Symposium PM2 : Plasma Processing via Liquid for Life Sciences and Environmental Applications

Plasma-activated medium (PAM) had been proposed as a new option of chemotherapy, and anti-tumor effects of PAM have been demonstrated for glioblastoma, ovarian, gastric, pancreatic, lung, and breast cancers through in vitro and in vivo experiments [1-4]. PAM is not limited for cancer therapy. For example, it was demonstrated that PAM was also useful for age-related macular degeneration [5]. For clinical applications of PAMs, understanding the molecular mechanisms is important, and effectiveness and safety tests through animal studies are inevitable [6-8]. We are challenging these issues to apply PAMs to medicine. PAMs were created by non-thermal atmospheric pressure plasma with ultrahigh electron density (approximately 2 x 10¹⁶ cm^-3). Diagnostics of gas phase and liquid phase for this plasma source were performed, and intracellular molecular mechanisms were investigated using several cell lines. It is concluded that PAMs roughly exhibit anti-tumor effects for most of cancer cell lines, however the sensitivities to PAMs are different from cells to cells. We are interested in the differences of sensitivities, especially selectivity between cancer cells and normal cells in PAM treatment. It was found that the PAM downregulated survival and proliferating signaling networks when the signaling pathways were constitutively activated. These results suggest that PAMs attack cancer specific signaling structures.The differences of sensitivities to PAMs are not only used for selective killing of cancer cells, but also select desirable cells (or eliminate undesirable cells). Thus, we will show a novel application that PAM is used to eliminate undifferentiated human induced pluripotent stem cells. Applications of PAMs are big challenges and creative ideas will broaden the ways in PAMs.To establish plasma medical science, understanding molecular mechanisms and effectiveness and safety tests are necessary.

[1] H. Tanaka, et al., Plasma Medicine, 1, 265-277 (2013).
[2] F. Utsumi, et al., Plos One, 8, e81576 (2013).
[3] K. Torii, et al., Gastric Cancer, 18, 635-43 (2014).
[4] N. Hattori, et al., Int J Oncol, 47, 1655-62 (2015).
[5] F. X. Ye, et al., Scientific Reports, 5, (2015).
[6] H. Tanaka, et al., Ieee Transactions on Plasma Science, 42, 3760-3764 (2014).
[7] H. Tanaka, et al., Physics of Plasmas, 22, 122003 (2015).
[8] H. Tanaka, et al., Clinical Plasma Medicine, 3, 72-76 (2015).

Immunomodulation, therapeutic interventions that change a patient’s immune responses, has become an attractive strategy for treatment of cancer.^[1] This approach aims to selectively kill cancerous cells while sparing normal tissue, by stimulating the body’s immune system to ultimately eliminate cancer.^[2] We have demonstrated that non-equilibrium atmospheric pressure plasma augments immune cell function in vitro in two ways:
1) Direct stimulation of immune cells with plasma ^{[3, 4]}
2) Indirect stimulation of immune cells via plasma induced immunogenic tumor cell death (ICD). Cancerous cells undergoing ICD express stress signals, known as damage associated molecular patterns (DAMPs), that can augment immune cell function.^[4]

This talk will discuss the translation of our in vitro observations to an in vivo mouse model. Using a nanosecond pulsed dielectric barrier discharge (nspDBD) plasma, we treated Balb/c mice with subcutaneous CT26 colorectal tumors. Following treatment, we saw increased immune cell recruitment and DAMP expression of cancerous cells in the local tumor environment. Furthermore, we saw development of a tumor specific, systemic immune response by quantifying specific T cells in the spleens of the mice. Taken together, we see that local plasma treatment can result in a specific and systemic immune response within the patient. This response has the potential to eliminate cancer and protect the patient from cancer recurrence.^[5] The implications of these effects of plasma on the clinical potential for treatment of cancers will be examined.
REFERENCES:

[1] Gea-Banacloche, Juan C., Principles of Molecular Medicine, Humana Press, pp 893-904, 2006.
[2] Mellman, I., G. Coukos, and G. Dranoff, Cancer immunotherapy comes of age. Nature, 2011. 480(7378): p. 480-489.
[3] Lin, A., et al., Uniform Nanosecond Pulsed Dielectric Barrier Discharge Plasma Enhances Anti-Tumor Effects by Induction of Immunogenic Cell Death in Tumors and Stimulation of Macrophages. Plasma Processes and Polymers, 2015. 12(12): p. 1392-1399.
[4] Miller, V., et al., Plasma Stimulation of Migration of Macrophages. Plasma Processes and Polymers, 2014. 11(12): p. 1193-1197.
[5] Kroemer, G., et al., Immunogenic Cell Death in Cancer Therapy. Annual review of immunology, 2013. 31: p.51-72.

Recent progress of medical application of atmospheric pressure plasma (APP) shows that the biological effects are mainly due to reactive oxygen and nitrogen species (RONS) in a liquid produced by exposure to APP. Especially, the contribution of hydrogen peroxide (H₂O₂) to the cellular responses, such as induction of apoptosis, was considered. Furthermore, nitrite (NO₂^-) and nitrate (NO₃^-) are also produced in a liquid exposed to APP in contact with ambient air. These nitrogen species have been also considered as a key factor in plasma medicine. Therefore, the production characteristics of RONS in a cell culture medium exposed to APP with different experimental parameters were investigated. Here, an atmospheric pressure plasma jet (APPJ) sustained by a pulsed power supply was used. In this study, applied voltages, feed gas (argon or helium), gap between the nozzle of APPJ and liquid surface, addition of oxygen in the feed gas, and humidification of the feed gas were examined. After APPJ irradiation to a cell culture medium, detection and quantification of RONS were conducted. It was shown that hydroxyl radical, peroxynitrite, NO₂^-, NO₃^-, and H₂O₂ were produced in the plasma-exposed cell culture medium. In addition, cellular responses of the plasma-irradiated cell culture medium in human lung cancer cell lines were also investigated. The correlation between the viability and the long-lived RONS in the cell culture medium will be discussed.

Photodynamic therapy (PDT) is a treatment modality that takes advantage of the cytotoxic effects induced by a light source and a photosensitizer to generate singlet oxygen species [1]. In this study, cold atmospheric plasma (CAP) [2], of which wavelengths are widely coverd from 250 nm to 800 nm, was used for the first time as a light source in photodynamic therapy. 5-ALA and gold nanoparticles 2-4 nm in diameter were encapsulated inside polymersomes by self-assembly. Both fibroblasts (ATCC, PCS-201-011) and melanoma A375 (ATCC, CRL-1619) cells were seeded on a 96-well plate maintained in DMEM (ATCC) supplemented with 10% FBS (ATCC) and 1% penicillin/streptomycin (Sigma). After 24 hours of incubation, polymersomes with different concentrations (from 100 to 500 μg/ml) were added to the cells and were further co-cultured overnight. Then, both cells with nanoparticles were exposed under a CAP light source for 90s. Cell viability of the two cell lines was quantified by an MTS assay, and cell morphology was observed under confocal microscopy. Cell viability results with the 5-ALA mediated photodynamic therapy indicated that using CAP as light source significantly decreased melanoma cell number when compared with non-CAP treatment. Specifically, at concentrations of 200 μg/ml, the melanoma cell number reduced by more than 50% when compared to controls. More importantly, this treatment was non-cytotoxic to healthy fibroblasts. In addition, confocal images indicated that the 5-ALA/PDT treated melanoma cells lost their cellular protrusions and showed a polygonal, nearly epithelial cell-like appearance in contrast to the elongated cells with multiple protrusions in untreated controls. All of these results showed that 5-ALA/ PDT with CAP as a light source is a novel effective PDT method for anti-tumor applications deserving further study.
Acknowledgement: This study was supported by Northeastern University.
References: [1] L. M. Rossi, P. R. Silva, L. R. Vono, et al. Langmuir, 2008, 24, 12534-12538.
[2] M. Wang, X. Cheng, W. Zhu, et al. Tissue engineering: Part A, 2014, 5(20), 1060-1071.

There is currently significant interest in the use of helium (He) and argon (Ar) plasma jets in a range of healthcare applications, which include wound and cancer therapy, sterilisation and surface disinfections. A strong link is emerging between the plasma generation of reactive oxygen and nitrogen species (RONS) and the outcomes in a range of biological and medical applications. However, gaps exist in our understanding between plasma-RONS generation and the controlled delivery of these RONS into solutions, tissue fluids and tissues. Herein, we investigate protocols for measuring the delivery of three RONS (hydrogen peroxide – H₂O₂, nitrite – NO₂^- and nitrate – NO₃^-) and molecular oxygen (O₂) through tissue models and into models of tissue fluids.

Whilst, direct plasma jet treatments deliver more RONS and O₂ into tissue fluid (than tissue) for equivalent treatments times, in the case of the former RONS delivery only occurs whilst the plasma jets are ignited; in the latter the transport of RONS through tissue continues well after the plasmas are extinguished. The He plasma jet tested was more effective at delivering H₂O₂ and nitrite directly into tissue fluid, but the Ar jet delivered more nitrate. The Ar plasma jet was also more effective at delivering nitrate deeper into tissue. In tissue, He vs Ar jet delivery of H₂O₂ was initially comparable. Interestingly, neither jet delivered significant nitrite into the tissue model.
Direct treatment of tissue fluid is deoxygenating, and a greater effect is seen with He (cf Ar). This effect is known as “sparging". In contrast, in the tissue models both jets oxygenated the subsurface. These results indicate that in the context of direct and indirect plasma jet treatments of real tissue and tissue fluids, the choice of process gas (He or Ar) and indirect (through tissue) and direct (blood) treatments could have a profound effect on the concentrations of RONS and O₂. Irrespective of operating gas, sparging of tissue fluid (in an open wound) for long prolonged periods during direct jet treatment, could have implications for healthy tissue function; whilst through-tissue plasma jet treatment may provide a method to reperfuse oxygen-starved tissue.
The assays we will describe can be readily adopted (by others) and may support the future development of plasma sources to deliver specific (metered) doses of RONS.

The combined plasma delivery of reactive oxygen and nitrogen species (RONS) and molecular oxygen (O₂) could offer a new avenue in developing effective therapeutic strategies for the treatment of diseased tissue. However, to ensure the safe and effective clinical use of plasma sources, it is essential to understand what (1) RONS are delivered, (2) the rate of delivery (3) the penetration depth of RONS into tissue and (4) how the tissue perturbs the delivery of RONS. In this presentation, I will focus on the fundamentals of how non-thermal atmospheric-pressure plasma jets deliver RONS deep within tissue (>> 1 mm). Our approach involves the use of agarose (and pig skin) targets as surrogates for real tissue [1,2], and synthetic cell models (phospholipid membrane vesicles with diameters of 100 nm to 2 mm) [3]. RONS are detected using embedded chemical reporters, or by in-situ UV absorption spectroscopy for the real-time detection of RONS. In addition, I will discuss how plasma jets can be effectively implemented for oxygenation of tissue fluid and tissue. The assays described in this paper support the future development of plasma sources that are designed to deliver highly-specific doses of RONS/O₂ for disease treatment (e.g. in cancer therapy).
References
1. Probing the transport of plasma-generated RONS in an agarose target as surrogate for real tissue: dependency on time, distance and material composition, E. J. Szili, J.-S. Oh, S.-H. Hong, A. Hatta, R. D. Short, Journal of Physics D: Applied Physics 48, 202001 (2015).
2. In-situ UV Absorption Spectroscopy for Monitoring Transport of Plasma Reactive Species through Agarose as Surrogate for Tissue, J.-S. Oh, E. J. Szili, N. Gaur, S.-H. Hong, H. Furuta, R. D. Short, A. Hatta, Journal of Photopolymer Science and Technology 28, 439 (2015)
3. Ionized gas (plasma) delivery of reactive oxygen species (ROS) into artificial cells, S.-H. Hong, E. J. Szili, A. T. A. Jenkins, R. D. Short, Journal of Physics D: Applied Physics 47, 362001 (2014).

Interest in plasma medicine continues to grow as the potential link between reactive oxygen and nitrogen species (RONS) and cellular signalling is being investigated. In order to establish a firm link between plasma-generated RONS and cellular signaling, accurate and reproducible procedures need to be developed to quantify the plasma delivery of RONS into biological systems. Ideally, these assays should be affordable and readily accessible in most laboratories without the need of sophisticated analytical equipment. Chemical reporters are ideally suited, because if used properly, can provide quantified data on RONS in solution, with affordable spectroscopic equipment (e.g. microplate reader for high-throughput measurement). For example, one of the most common reporters (used for more than 50 years) is 2′,7′-dichlorodihydrofluorescin (DCFH), which is a broad range RONS reporter. In the presence of RONS, the dye is converted into a green fluorescent product. But the measurement of RONS with chemical reporters is likely to be affected by variables such as the composition of the solution and UV light. Artifacts may arise due to interaction between the dye and molecular oxygen, cross-reactivity between RONS and photo-oxidation of the dye. In other words the change in intensity of the probe is not solely an outcome of reaction with RONS. In this talk, I will discuss in detail how to mitigate the above issues in order to provide reliable and accurate measurements on the plasma delivery of RONS into biological systems. The protocols described in this talk can be readily adopted by other researchers to assess the delivery of RONS into tissue fluid and tissue.

Attaching biomolecules to surfaces is a complex process and usually involves multiple steps including surface preparation, depositing primer layers, attaching linker chemistries and then using complex wet chemical processing to finally bond the target molecule to the surface. This has rendered the process time consuming, complex and difficult to control in an industrial setting. Here, we report on how plasma can offer a one-step tool that delivers equivalent or superior coatings in an easy to operate, clean and controlled process. The simplicity and uniformity of the process opens up a wide range of potential applications. These can range from attaching proteins for diagnostics, improving the biocompatibility of medical implants and even as far as direct placement of biological materials onto wound sites to enhance healing. In this talk, we will review the state of art and provide insight into how the process can be controlled for optimum performance.

We have successfully carried out local reagent injection and perforation to materials of variety of hardness using bubble cavitation and plasma cavitation. Cavitation and plasma was generated by pulse discharge of microelectrode having special tip structure. Injection to soft material such as animal cell was performed only by cavitation of directional high-speed ejected micro-bubbles, whilst the perforation to hard materials such as plants cells or metals were achieved by synergistic effect of cavitation of bubble and plasma ablation. The novel device we proposed has ability to perforate wide range of materials with high dynamic range without changing the setting. The talk is especially focusing on the plasma-induced bubbles in micro-fluidic environment and its applications to bio-medical fields. It is important to note that the applications are not only the local regent injection and perforation to materials of variety of hardness, but also the molecular condensation system using reactive air-liquid interface of electrically-induced bubbles. One of the applications is the protein crystallization by using plasma-induced bubbles. The plasma-induced bubbles can contribute to wide range of research fields such as gene therapy including direct gene injection to biological materials of variety hardness and new material development and so on.

Artificial introduction of cell-impermeable molecules, such as DNA, RNA, proteins, antibodies, and dyes have been used in various field such as life science, medicine, pharmacy, and agriculture. In particular, gene transfection, which is a fundamental technique used to deliver nucleic acids into mammalian cells, is widely used for experimental and therapeutic purposes. For example, viral vector, electroporation, lipofection, and sonoporation methods have been used for introducing foreign DNA. These methods have both advantages and disadvantages for efficiency, viability, running cost, safety and so on. Therefore, the more safe, effective, and low-cost novel transfection method should be developed.
In this study, we have demonstrated a method for gene transfection quite different from conventional one. This method is based on water-in-oil droplet manipulation by using electrostatic force. When a water droplet is placed in oil, it is driven reciprocally between a pair of electrodes by applying a DC electric field. This droplet motion is brought about as follows when the DC voltage is turned on, a droplet is carried to one electrode by Coulomb force possibly due to inherent charge. When the droplet touches to the electrode, it is charged with the same polarity as the electrode. The droplet then starts to move to the other electrode and the same process occurs repeatedly. In this process, local and intense electric field is applied to the droplet in a very short time when it touches the electrode. This local intense electric field must work on a gene transfection. We have investigated a novel gene transfection by using the droplet containing cultured mammalian cells and foreign plasmid DNA. The transfection efficiency was obtained and compared with that of the lipofection.

Atmospheric pressure plasma is applied as a novel and valuable tool in the fields of biology and medicine, for the various purposes such as selective killing of tumor cells, sterilization, hemostasis, and gene transfection. Reactive oxygen and nitrogen species (ROSs and RNSs) produced by atmospheric pressure plasma would play crucial roles for those plasma-induced biological reactions. However, many aspects are still unclear how ROSs and RNSs affect and/or pass through cell membranes. Artificial lipid bilayers are useful cellmembrane model systems for investigating the fundamental interaction between cell membranes and chemical and biological agents. Recently, we investigated the effects of atmospheric pressure plasma on the basis of dielectric barrier discharge (DBD) on a supported lipid bilayer (SLB), which is an artificial cell membrane system formed at a solid-liquid interface [1]. In this study, we showed the degeneration of SLB in its physical properties, and considered the cause of these phenomena by ROS.
DOPC (dioleoylphosphatidylcholine) and Rb-DOPE (rhodamine B dioleoylphosphatidyl-ethanolamine) were used as a lipid and fluorescent dye-labeled lipid, respectively, and SLB consisted of them. SLB was prepared in a buffer solution (pH 7.4) by the vesicle fusion method, and introduced into a DBD-plasma irradiator [1], which was settled in a glove box and filled with He. We applied AC high voltage at 15 kHz for the DBD-plasma irradiation of DOPC-SLB with the electric energy in the range of 4.1 − 20.9 kW s. We observed the morphology of DOPC-SLB using an epi-fluorescence microscope (epi-FM) and atomic force microscope (AFM), and measured its fluidity by fluorescence recovery after photobleaching (FRAP) method [1]. After the DBD-plasma irradiation of 4.1 − 8.2 kW s, the FRAP results showed that the fluidity of the DOPC-SLB reduced approximately 30%, even though there was almost no change in the membrane morphology. By further irradiation of 11.5 − 20.9 kW s, micropores appeared on the DOPC-SLB and their number density increased with the irradiation energy. Assay using ROS-sensitive fluorescence probes which can detect peroxynitrite(ONOO^-) and hydroxyl radical(OH) [2] indicated the degeneration of these species in the buffer solution by the plasma irradiation. And from the result of the assay, the major species in the buffer solution were suggested to be OH. It seems reasonable that plasma-generated OH induced the oxidation of the acyl chain in DOPC, which propagated consuming dissolved O₂ in the hydrophobic region of bilayer and degenerated the DOPC-SLB fluidity and structure.
References
[1] R. Tero, et al., Appl. Phys. Express, 7, 077001 (2014); Y. Suda, et al., Jpn. J. Appl. Phys., 54, 01AF03 (2015); Y. Suda, et al., Jpn. J. Appl. Phys., 55, 03DF05 (2016).
[2] K. Setsukinai et al., J. Biol. Chem., 278, 3170 (2003).

We developed a sterilization technology by pulsed discharge plasma in water for the purpose of reduction of the microorganisms which existed in condensed water exhausted from an air-conditioner. In this paper, we report the generation characteristic of OH radicals by using pulsed discharge plasma in water, and the bactericidal effect using pulsed discharge plasma in the condensed water, and discuss the sterilization mechanism of pulsed discharge plasma in water.
We found the following things, as a result of investigating the sterilization technology by pulsed discharge plasma in water.
(1) Luminescence of OH radicals and Hα radicals, etc. is seen in pulsed discharge plasma in the condensed water. The luminescence intensity of the OH radicals is decreased with decreasing applied voltage regardless of the wire diameter of a high-voltage. The amount of hydrogen peroxide generation increases in proportion to luminescence intensity of OH radicals.
(2) The bactericidal effect increases with increasing input power and electrical conductivity. But the bactericidal effect decreases with increasing total organic carbon concentration. The pulsed discharge plasma in water can sterilize various kinds of microorganisms, but the bactericidal effects depend on microbial species. The effect decreases in the order of bacteria> yeasts> fungi. Although these microorganisms coexist in the actual condensed water, the pulsed discharge plasma underwater can sterilize them all.
(3) As treatment time by pulsed discharge plasma in water becomes longer, the amount of bacteria is reduced and the hydrogen peroxide concentration is increased. On the other hand, feeding of hydrogen peroxide every one hour did not reduce the amount of bacteria. Therefore, the sterilizing effect of the pulsed discharge plasma treatment is not due to hydrogen peroxide.
(4) The survival rates after one-hour discharge treatment by pulsed discharge plasma in water was correlated with the luminescence intensity of OH radicals. This result suggests the contribution of OH radicals to the sterilization ability. But the sterilization performance was about the same, though the luminescence intensity was different when pulsed discharge plasma of 3mm in diameter was compared with that of 2mm in diameter. From the evaluation of the structure of microorganisms after treatment by pulsed discharge plasma in water, ultraviolet rays generated by the discharge may also contribute the sterilization ability. The sterilization capability by pulsed discharge plasma in water is dependent on the amount of OH radicals and ultraviolet rays.

Atmospheric pressure plasma (APP) emerged as a promising tool in medicine and has been shown effective for cancer, wound, dental, and esthetic treatments both in vitro and in vivo studies. More recently, there have been growing interests in applying the APP for food processing and agriculture, thanks to its antimicrobial functions either by killing microbes or by inhibiting the growth of microbes. At high enough dosage, bacterial cells were destructed completely, but there remained concerns on whether the harsh conditions would not compromise the quality the foods or agricultural products. Therefore, it would be desired to find the optimal treatment condition at which the bacterial cells would be deactivated while the quality of the products is preserved. In our study, we investigated the minimum dosage of the APP at which the microbial growth and motility were effectively suppressed so that these deactivated cells would not be able to infect host cells when consumed along with the foods. In the context of agriculture, we also employed the APP to treat soil living nematodes. Both the nematode motility and the hatching rate of the eggs were reduced by more than 50% after a short exposure to the APP. The plasma contains numerous effectors, both chemical and physical, which include charged particles, reactive oxygen species (ROS), nitric oxides, ozone, UV, and electric current. These reactive compounds can interact with living targets and alter their physicochemical properties. In particular, ROS has been identified as a predominant key factor in the plasma-induced processes. Also, the effects of ROS would differ depending on the subject of interest. Under an identical treatment condition, cancer cells die while the other healthy cells remain intact because the intrinsic intracellular level of ROS is different between two cell types, leading only the cancer cells to go above the threshold to be apoptosized. Likewise, epithelial cells undergo apoptosis while fibroblasts do not under the same treatment condition, likely due to the different levels of antioxidants that scavenge the intracellular ROS. The very same treatment condition that destroys the bacteria would inhibit the growth and motility of nematodes, due to the difference in ROS managing capacity.

Non-equilibrium cold atmospheric pressure plasma (CAP) generates a complex cocktail of reactive oxygen and nitrogen species (RONS) in open air environments which enable the inactivation of many pathogens. CAP is particularly an effective disinfection tool for heat sensitive items as it operates at close to room temperature conditions.

We present a study of virus inactivation by a two-dimensional array of micro dielectric barrier discharges, operating with an air flow through it, allowing for large area treatments. In this work, feline calicivirus, a surrogate of human norovirus that is responsible for many gastroenteritis outbreaks, is studied. Virus suspended in solution and applied on dry stainless steel discs has been studied and the inactivation efficiency is compared.

In case of the plasma treatment of virus on stainless steel discs, humidity is found to significantly enhance virus inactivation. Comparing the O₃ densities for the used plasma conditions with previous studies using ozonizers suggests that the densities and contact time are sufficient to explain the inactivation of virus by O₃. The inactivation of virus in solution is much less efficient. This suggests that the O₃ transfer is limited due to the absence of liquid stirring. The virus inactivation in solution correlates with a change in the pH and the measured NO₂^- concentration suggesting an involvement of RNS in the solution phase inactivation.

Atmospheric pressure plasmas are a rich source of reactive oxygen and nitrogen species (RONS) that can inactivate bacteria. Many studies on the inactivation of planktonic bacteria have been reported although most studies have achieved diminished bacterial inactivation when using buffered solutions. The inactivation has often been shown to require a reduction in pH in combination with the production of H₂O₂ and HNO₂ leading to peroxynitrate chemistry. We report a study of bacterial inactivation (Pseudomonas aeruginosa (PA14) and Staphylococcus aureus (USA300)) in saline and phosphate buffered saline (PBS) in vitro for both planktonic bacteria and biofilms. We successfully inactivated bacteria in both liquid and biofilm phases. Short lived species play a role in inactivating bacteria in the case of Ar plasma. Long lived OCl^- plays a role in case of Ar + 1% O₂/air plasma. The inactivation is successful even in buffered solution although it requires the presence of Cl^- in the case of Ar + 1% O₂/air plasma. The underlying mechanism of the inactivation will be discussed in detail.

Non-equilibrium atmospheric pressure plasmas interacting with liquids offer a unique source of highly reactive chemistry beneficial for many applications in biology, medicine and advanced materials manufacturing. Plasma-liquid interactions can involve synthesis of nanoparticles (NPs). While the technical capability and application potential are clear, the underlying mechanisms of these processes are poorly understood.

The presentation will discuss the reaction pathways responsible for the synthesis of AgNPs at the plasma-liquid interface. This will include a detailed analysis of the reduction mechanism of Ag⁺, the initial step for the formation of NPs in solution, through various plasma produced species including solvated electrons, UV photons and hydrogen atoms. The effect of plasma on surfactants (like fructose) and the involvement of the surfactant in the synthesis process will also be elucidated.

Electrical discharge plasmas in liquids have been studied for a number of years for applications in different environmental, biological or medical applications. However, the physics underlying the complex phenomena of electric discharge formation in liquid media as well as the chemistry of plasma/liquid interactions induced by these discharges is not fully understood. OH radical is one of the most strongly oxidative species produced by plasma in water and is also building block of H2O2 which is an important agent in the chemical activity of plasma-liquid systems. So far, pulse durations applied for generation of discharge plasmas in liquids were typically in the range of microseconds. The average energy of electrons formed by streamer-like discharges in water was estimated to be 0.5–2 eV. This would be sufficient to cause only vibration and rotational excitation rather than electron dissociative reactions of water. Therefore, metastable induced or thermal dissociation of water molecules and electron dissociative recombination of water ions are proposed as more likely pathways of plasmachemical production of OH radicals in water. Recently, a fundamentally different type of discharge generated in water by application of high-voltage pulses with nanosecond duration was reported by several authors. The observed discharge was reported to have a different nature from the discharges with microsecond pulse duration. This suggests, that it might be possible to vary electron energy distribution in the discharge and plasmachemical processes in water by pulse duration of pulsed power used for discharge in water.

In this work, nanosecond pulsed corona discharge in deionized water was studied by means of time resolved optical emission spectroscopy and by chemical methods. FID generator was used for high-voltage pulse generation of pulse length 7 ns (FWHM) and amplitude up to 110 kV. Chemical activity of the nanosecond discharge was evaluated by measuring the hydrogen peroxide production in water and using phenol as chemical probe. Comparison with the pulsed discharge plasma in liquid operated in microsecond pulse duration range was made in order to assess effects of the input pulse power parameters (pulsed duration) on plasmachemical processes induced by electrical discharge plasma in the liquid. Fundamental issues regarding the mechanism of OH radical formation by the discharge plasma in water will be addressed.

This work was supported by the Czech Science Foundation (project 15-12987S).

Recently, we have shown that atmospheric pressure dielectric barrier pressure (DBD) plasma irradiation to plant seeds can induce continuous growth enhancement of the plants, shorten the harvesting period, and improve significantly the crop yield [1-5]. Reactive oxygen species (ROS) and reactive nitrogen (RNS) produced by plasmas often interacts with living cells surrounded by water. Therefore interaction among plasmas, water, and seeds is an important research topic. Here we have demonstrated that air, O₂ and N₂ atmospheric pressure DBD plasma irradiation to DI water, that is, plasma activated water (PAW) induces growth enhancement of plants. Experiments were carried out with a scalable DBD device [1-5]. The device consisted of 20 electrodes of a stainless rod of 1 mm in outer diameter and 60 mm in length covered with a ceramic tube of 2 mm in outer diameter. The electrodes were arranged parallel with each other at a distance of 0.2 mm. We employed a 8x12 formatted 96-well microplate of 1ml capacity for each well filled with DI-water. The microplate was set at 3 mm below the electrode. Plasma of O₂, Air and N₂ gas was irradiated to DI-water for 180s to make PAW. The discharge voltage and current were 9.2 kV and 0.2 A. Then, PAW was keep for 1 hour and 1 day in room temperature. 10 radish sprout (Raphanus sativus L.) seeds were put into petri dish filled with 1,3,5 and 10 ml of PAW. The plants from these seeds were cultivated under dark condition in 3 days. The seedling length was analyzed statistically with tukey test one side anova. For 1 hour PAW the seedling length after 3 days cultivation is 70%, 50% and 15% long for O₂, Air and N₂ plasmas compared to control, whereas 1 day PAW the length it is 62%, 47% and 8% long for O₂, Air and N₂ (P<0.05). Therefore, long lifetime ROS is effective for the growth enhancement, while short lifetime ROS is very effective as previously reported [5].
This work was supported by MEXT KAKENHI Grant No. 24108009 and JSPS KAKENHI Grant No. 24340143.
S. Kitazaki, D. Yamashita, H. Matsuzaki, G. Uchida, K. Koga, M. Shiratani, N. Hayashi, TENCON 2010 - 2010 IEEE Region 10 Conference (2010) 1960.
S. Kitazaki, K. Koga, M. Shiratani, N. Hayashi, MRS Proceedings 1469 (2012) mrss12-1469-ww02-08.
S. Kitazaki, T. Sarinont, K. Koga, N. Hayashi, M. Shiratani, Curr. Appl. Phys. 14 (2014) S149.
K. Koga, S. Thapanut, T. Amano, H. Seo, N. Itagaki, N. Hayashi, M. Shiratani: Appl. Phys. Exp. 9 (2016) 016201.
T. Sarinont, T. Amano, P. Attri, K. Koga, N. Hayashi, and M. Shiratani: Arch. Biochem. Biophys (2016) http://dx.doi.org/10.1016/j.abb.2016.03.024.

Electrical discharge plasma is an effective and versatile advanced oxidation process due to the formation of reactive species such as hydroxyl radicals, hydroperoxyl radicals, and hydrogen peroxide. Plasma treatment also includes a broad range of other treatment mechanisms, including electron-based reduction, UV radiation, cavitation, and thermal degradation.
Despite promising results of bench-scale studies and evident potential advantages of plasma water treatment, the technology has not been used in practice. A major obstacle hindering the progress in developing plasma reactors is associated with the absence of general principles to guide the design of new reactors with higher efficiency. In an attempt to improve the feasibility of plasma-based water treatment technology and develop basic guidelines for reactor design and optimization, we have determined that the size of the contact area between the plasma and the treated solution is the single most important factor affecting the plasma reactor performance. Building on this knowledge, we have modified the traditional gas-discharge plasma reactor to maximize this contact area, which resulted in the development of the enhanced contact plasma reactor. The enhanced contact electrical discharge plasma reactor rapidly and efficiently degrades many chemicals including pharmaceuticals, personal care products, disinfection byproducts, and several perfluoroalkyl acids (PFAAs). Of all the compounds evaluated, perfluorooctanoic acid and perfluorooctanesulfonic acid were degraded the fastest.
We have determined the efficacy of the plasma process for treatment of a wide range of different compounds of environmental importance and used the results of this investigation to construct a model to predict the approximate treatability of any compound based on just a few of the compound’s physical properties. We have determined design guidelines for plasma reactor scale up as well as the efficiency and relative competitiveness of the scaled up process for selected compounds.

Gas-liquid electrical discharge plasma reactors have been extensively evaluated for the degradation of many organic compounds in the liquid phase. Such plasma reactors have been shown to produce a range of oxidizing and reducing species and of particular importance is the efficient production of the hydroxyl radical. Hydroxyl radicals are formed at and near the interface of the plasma with the liquid phase and can lead to the degradation of organic compounds dissolved in water. The water pollutant 1,4-dioxane is widely present in groundwater that contains trichloroethane (TCA) and/or trichloroethylene (TCE), and despite the widespread attention on the removal of TCA and TCE from groundwater, only more recently has attention been directed at 1,4-dioxane. While 1,4-dioxane is not easily biodegradable it does react with hydroxyl radicals to produce biodegradable products. In this study we report on the combination of a gas-liquid non-thermal plasma reactor for the initial oxidation of dioxane and a bioreactor for further degradation of products.

The application of air non-thermal plasma above the water surface is becoming a realistic alternative to the more established advanced oxidation processes for water remediation [1]. In these systems a humidified air flow above the water is subjected to an electrical discharge generating an air plasma which contains reactive oxygen species, such as ozone and OH radical, able to oxidize the organic pollutants until CO₂ and H₂O. Two prototype reactors for the degradation of organic pollutants in which plasma is produced by corona or dielectric barrier discharges (DBD) in the air above the liquid have been developed and extensively characterized at the Department of Chemical Sciences of the University of Padova [2-4]. The reaction mechanisms and the role of the major oxidizing species, ozone and hydroxyl radicals, were investigated through the study of the oxidation process of well known models, such as phenol and t-butanol. Most useful was the comparison with experiments of ozonation, for which rate constants are available in the literature, and the use of gases different from air, notably nitrogen and argon. The role of nitrogen reactive species was also analyzed. It was found that the concentration of species containing nitrogen is negligible when air is used to generate the plasma. The study was thus extended to investigate on the efficiency of the system in the oxidation of emerging organic pollutants [5]. The CO₂ produced in the degradation process of pharmaceuticals, pesticides and perflurinated alkylated substances was quantified by FT-IR and the oxidation intermediates were analyzed by LC/UV-Vis and LC/ESI-MSⁿ. Despite its simplicity, our plasma reactors proved to be effective in the complete conversion of various compounds into CO₂.
An account of these results will be given with particular attention to the most recent findings regarding emerging organic pollutants.

[1] B. Jiang, J. Zheng, S. Qiu, M. Wu, Q. Zhang, Z. Yan, Q. Xue. Chem. Eng. J. 2014, 236, 348.
[2] E. Marotta, M. Schiorlin, X. Ren, M. Rea and C. Paradisi, Advanced oxidation process for degradation of aqueous phenol in a dielectric barrier discharge reactor, Plasma Process. Polym. 2011, 8, 867.
[3] E. Marotta, E. Ceriani, V. Shapoval, M. Schiorlin, C. Ceretta, M. Rea and C. Paradisi, Characterization of plasma-induced phenol advanced oxidation process in a DBD reactor. Eur. Phys. J. Appl. Phys. 2011, 54, 13811.
[4] E. Marotta, E. Ceriani, M. Schiorlin, C. Ceretta and C. Paradisi, Comparison of the rates of phenol advanced oxidation in deionized and tap water within a dielectric barrier discharge reactor. Water Res. 2012, 46, 6239.
[5] S. Krishna, E. Ceriani, E. Marotta, A. Giardina, P. Špatenka, C. Paradisi. Products and mechanism of verapamil removal in water by air non-thermal plasma treatment. Chem. Eng. J. 2016, 292, 35.

Recently, atmospheric-pressure plasmas in contact with liquid are energetically studied. We have studied the gas-phase and liquid-phase reactions in atmospheric-pressure DC glow discharge with liquid electrode [1]. The DC glow discharge with liquid electrode is considered as electrolysis with plasma electrode, which supplies electrons or positive ions to the liquid surface. By the electron irradiation of the aqueous solution surface, Au and Ag nanoparticles (NPs) are easily synthesized through the reduction of Au³⁺ and Ag⁺, respectively [2].
In this work, we studied the synthesis of ferromagnetic NPs from iron ion by the plasma-induced electrochemical reaction. Since the reduction of Fe²⁺ was difficult in the aqueous solution, we attempted the synthesis of magnetite NPs. Magnetite is iron oxide consisting of Fe²⁺ and Fe³⁺, therefore, the ratio of Fe²⁺ and Fe³⁺ during the synthesis is important. We used a magnetite NPs synthesis system with combination of iron electrolysis and plasma electrolysis, in which Fe²⁺ was supplied by iron electrolysis, a part of Fe²⁺ was oxidized into Fe³⁺, and the electron irradiation of the liquid surface induced the rapid synthesis of magnetite NPs. The experimental setup is as follows. A stainless-steel nozzle electrode as a cathode with inner and outer diameters of 500 μm and 800 μm, respectively, is placed at 1 mm above the solution surface, while iron electrode is immersed in the solution as an anode. He gas is injected from the nozzle electrode, and the He flow is surrounded by the sheath flow of N₂ to prevent the unnecessary oxidation. By applying a DC voltage between the nozzle and iron electrodes, a stable glow discharge is obtained in contact with liquid. NaCl aqueous solution is used as electrolyte.
We confirmed the faster synthesis of magnetite NPs using plasma without adding any chemicals than the conventional coprecipitation method. Then, the question is what reactions are promoted to synthesize Fe₃O₄ by the plasma-induced reaction. The synthesis of magnetite NPs depended on the discharge current, liquid conductivity, local pH of the solution, and the dissolved oxygen (DO) concentration. The initial DO concentration strongly affected the oxidation rate of Fe²⁺ into Fe³⁺ judging from the color change of the solution. The consumption of DO using plasma was much faster than the natural oxidation of Fe²⁺. We also found that high liquid conductivity caused the low DO concentration due to the salting-out effect. Therefore, the reaction between DO and plasma-induced species such as hydrated electron will be the important factor for the magnetite formation.

Acknowledgement: This work was supported by JSPS KAKENHI Grant Number JP15H03584.

[1] F. Tochikubo et al., Jpn. J. Appl. Phys. 53, 126201 (2014)
[2] N.Shirai et al., Jpn. J. Appl. Phys. 53, 046202 (2014)

We reported an approach to produce nanostructured polycrystals in the form of films by first crystallizing the “grains” first as ligand-capped nanocrystals synthesized in solution as colloids, then depositing them by self-assembly, and finally removing the ligands by plasma processing (i.e., “nanocrystal plasma polymerization”, NPP). Since this approach bypasses stochastic bulk nucleation, it can form polycrystals with uniform, nanoscale grain sizes, but the evolution of the structure, composition, and cohesiveness of the films during the removal of the ligands is unclear. For example, it is not known whether trace amounts of carbon remain behind between the particles, whether bonds are formed between the particles, and how the plasma successfully removes organics from the inside of these films. In this work we answer these questions by an integrated analysis of the morphology, composition, and mechanical properties of colloidal nanocrystal assemblies during the removal of the ligands by O2 plasma.
We will describe the structural, chemical, and mechanical evolution of films of colloidal nanoparticles upon exposure to an O₂ plasma (500 mTorr, 7 W, 6 h to 168 h of exposure). The particles in the arrays are initially separated by organic ligands (trioctyphosphine oxide, TOPO) that bind to the particle’s surface through the phosphine oxide group. The plasma removes the alkyl tails of the ligands over the course of several hours (carbon concentration is 1.3 ± 0.5 at. % after 168 hrs). Before finally settling into an all-inorganic polycrystal, the arrays go through an intermediate, highly porous state (~0.5 void fraction) where the particles are joined by necks of ligand molecules. This highly porous state obtained after ligand removal result in high surface area materials with 100% crystallinity, good mechanical properties, and bare inorganic surfaces that could be very attractive for any application involving interface processes (e.g., energy storage, photovoltaics, catalysis) and the study of these processes as a function of material structure

References:
Nanocrystals as Precursors for Flexible Functional Films
L. Cademartiri*, G. von Freymann, A. C. Arsenault, J. Bertolotti, D. S. Wiersma, V. Kitaev, G. A. Ozin*
Small 2005, 1 (12), 1184-1187
Building Materials from Colloidal Nanocrystal Arrays: Preventing Crack Formation During Ligand Removal by Controlling Structure and Solvation
S. Shaw, B. Yuan, X. Tian, K. J. Miller, B. M. Cote, J. L. Colaux, A. Migliori, M. G. Panthani, L. Cademartiri*
Advanced Materials, accepted
Evolution of the Structure, Composition, and Mechanical Properties of Colloidal Nanocrystal Films Upon Removal of Ligands by O₂ Plasma (communication)
Santosh Shaw, Julien L. Colaux, Jennifer L. Hay, Frank C. Peiris, Ludovico Cademartiri*
Advanced Materials, revision submitted

Ferromagnetic shape memory alloys are an upcoming class of smart
materials with strong magneto-mechanical coupling, that have been attracting
increasing interest during the past years. Exhibiting magnetization changes
upon straining and, vice versa, reversible strains of several percent in response
to an external magnetic field, they are perfectly suited for biomedical
sensing or actuation. This particularly holds true as they can be operated
at constant (body) temperature at frequencies ranging from quasi-static to
some kHz. In contrast to the "prototype" Ni-Mn-Ga alloy, where the FSM effect
was initially discovered, Fe-Pd FSM alloys reveal excellent "basic" biocompatibility,
which makes them hot candidates for in-vitro and in-vivo use. For use in cell and tissue actuators or strain sensors, sufficient adhesion to
mediate strains clearly constitutes a prerequisite.

When contacting functional hard materials to biomedical applications, control of
interfaces with cells and tissue constitutes one of the largest challenges.
Assembly of biomolecules within an inert-gas-plasma constitutes a novel
approach to synthesize strongly adherent bioactive coatings that dramatically
enhance coupling to living matter. As proof of concept we demonstrate
plasma assisted functionalization with
the amino-acid, L-lysine, by plasma-treatment, resulting in flexible, yet
ultra-durable coatings. Containing high amounts of NH2 functional groups,
they mediate strong adhesion of cells and tissues, which is
is confirmed by cell tests with NIH/3T3 embryonic murine fibroblasts. In doing
so, we demonstrate excellent biocompatibility, exceeding conventional
poly-L-lysine coatings in terms of cells focal adhesion density. The binding
chemistry behind these scenarios are unraveled by employing ab initio
computer calculations.

[1] U. Allenstein, F. Szillat, A. Weidt, M. Zink and S. G. Mayr,
J. Mater. Chem. B, 2 (2014) 7739-7746
[2] M. Zink, F. Szillat, U. Allenstein and S. G. Mayr, Adv. Func. Mat. 23 (2013) 1383.

In this work, we apply one-step direct current arc discharge method to synthesize highly concentrated graphite-encapsulated magnetic nanoparticles functionalized with amino groups uniformly without further modification or any other pre/post-treatment procedures. The synthesis was accomplished by adding different volume ratios of NH₃ into He/CH₄ gas mixture under various gas pressures. The optimized number of functionalized amino groups is calculated to be ~3.22×10⁵ per nanoparticle prepared at 50 Torr with 0.1% of NH₃. As the volume ratios of NH₃ decrease from 1.0% to 0.1%, the optical emission peaks of CN and NH are intensified gradually, and the surface structural integrity also increases. These results indicates that NH₃ not only provides -NH/-NH₂ functional groups to incorporate with the dangling bonds activated by H radicals, but also constructs networks to flatten the outmost graphitic surfaces of encapsulated nanoparticles. As the working gas pressure changes from 25 Torr to 100 Torr, the outmost shells formed by the dissociated CH₄/NH₃ molecules tend to be relatively less disordered.

Plasma polymer thin films are of great interest in surface engineering in a wide range of applications. Herein, by using soft atmospheric plasma deposition conditions and by adapting these conditions to the used perfluorodecyl acrylate (PFDA) and dodecyl acrylate (DOCA) precursors[1], it appears possible not only to get a high retention of monomer functionalities but a co-polymerization close to conventional methods. In fact plasma copolymerisation highlighted the recent years promising and interesting prospects to tailor the surface by mixing antagonist precursor [2]. Moreover superhydrophobic coating have attracted significant attention nowadays. These coating showed interest applications in human life for antibacterial activities purposes for example thanks to their low surface energy and high repellency. In order to expand their use and to control the surface wettability from superhydrophobic to hydrophobic properties, the ratio of both previous monomer have been adjusted leading to copolymer of pp(PFDA-co-DOCA). The surface wettability have been characterized by means of water contact angle and the hysteresis have been evaluated in order to determine the wettability regime from cassie-baxter to wenzel.
In order to explain the wettability properties of the different ratio of co-monomer chemical, topographical and molecular investigations have been performed.
FTIR, XPS, NMR have been performed on deposits in order to gain chemical information. AFM and SEM provided topographical characterization of the deposits. Moreover in order to prove the copolymerization mechanism between both monomer during atmospheric plasma a new powerful tool mass spectrometry will be proposed.
Finally, antibacterial performances of the different plasma coatings will be discussed in function of the wettability properties.


[1] J. Petersen, C. Becker, T. Fouquet, F. Addiego, V. Toniazzo, A. Dinia and D. Ruch, RSC Advances, 2013, 3, 4416-4424.
[2] C. Chahine, F. Poncin-Epaillard, D. Debarnot, Plasma Process Polymer, 2015, 12, 493-501.

Nano-carbons like Grapnenes have greatly been interested in various fields of researches,where the large scale synthesis of nano-carbon should be free from using excess energies for firing, sintering, melting,vaporizing and/or expensive equipments. We, propose here Soft processing of functionalized Graphenes at ambient conditions. The Soft processing provides number of advantages which includes (a) simple reaction set up,(b) at ambient conditions, (c) simple procedure and (d)less operating costs and wastes.
In the present study, we have utilized “Submerged Liquid Plasma [SLP]”[1-4] and “Electrocemical Exfoliation[ECE] methods. In the ECE, graphite anode is exfoliated electrochemically by H₂O₂-NaOH[5,6] or Glycine-H₂SO₄[7] aqueous solutions under ambient temperature and pressure,for 5-30 min with +1-+5 volt, into 3-6 layers Graphene Nanosheets[GNs]. Those conditions are much milder than those reported before using other chemicals like ionic liquids and/or H₂SO₄-KMnO₄,etc.,because O₂^2- ions or ionic complex like Glycine-HSO₄^- would assist the exfoliation of graphite layers. Our products:GNs suspended in solutions can be transformed in the 2nd step in the same container using BrCH₂CN/dioxane into N-FG, further into Au-Hybridized N-FG by the sonification with Au nanoparticles. We have confirmed the excellent catalytic performance of those hybrids[5,6] It should be noted that Soft Processing can directly produce “Graphene Ink”;Graphenes dispersed in various liquids, under mild conditions..
References
1) J. Mater Chem A,(2014) 2, 3332; 2) Scientific Reports, 4(2014), 04395; 3) Carbon,78
(2014),446; 4) J. Mater Chem A, 2015, 3,3035-3043,5) Sci. Rep. 4 ,4237 (2014); 6) Nanoscale
(2014) 6,12758; 7) Adv. Funct. Mater. 2015, 25, 298-305.

Nano-carbons like Graphenes have greatly been interested in various fields of research including Biomedical areas. We believe that the large scale synthesis of nano-carbon should be free from using excess energies for firing, sintering, melting and/or expensive equipments. We, propose here Soft processing of functionalized Graphenes at ambient conditions. The Soft processing provides number of advantages which includes (a) simple reaction set up,(b) at ambient conditions, (c) simple procedure and (d)less operating costs. In the present study, we have utilized “Submerged Liquid Plasma [SLP]” methods. SLP methods resulted the direct synthesis of Nitrogen functionalized Graphene Nano-sheets from Graphene suspension and/or Graphite electrode in acetonitrile liquids.[1,2] Products contains few layers (< 5) Graphene nanosheets. Unsaturated or high energy functional group (e.g. C＝C, C＝N and C≡N) have formed in the products. We could confirm those functionalized Graphenes are electrochemically active. Using pencil rods instead of Graphite rods we have also succeeded to prepare the Nano-clay/Graphene hybrids by this SLP methods [3]. Reduction and functionalization of Graphene oxides [2] and Synthesis of Graphene/Au Hybrids [4] also realized by SLP. It should be noted that Soft Processing can directly produce “Graphene Ink” where Graphenes dispersed in various liquids, under mild conditions..
References
1) J. Mater Chem A,(2014) 2, 3332; 2) Scientific Reports, 4(2014), 04395; 3) Carbon,78
(2014),446; 4) J. Mater Chem A,(2015) 3, 3035

One of our research interests is the decomposition of persistent organic compounds, e.g., acetic acid and perfluorooctane sulfonate (PFOS), in water using plasmas. PFOS is one of excellent surface-active agents; however, PFOS is toxic and has substantial bioaccumulation and biomagnifying properties. We achieved a very high energy efficiency in the decomposition of PFOS using plasmas generated within gas bubbles compared with that using other methods such as sonochemical reactions. It is proposed that the thermal cleavages of the C–C bonds of PFOS molecules occurred successively at the plasma–liquid interface because they adsorbed on the interface. However, as gas supply is necessary for the plasma generation, we used a diaphragm discharge for the decomposition of PFOS. The reactor consisted of two solution containers separated by a ceramic plate with a small hole, and each container had an electrode. An AC voltage at 20 kHz was applied to the electrodes to generate a diaphragm discharge in the hole. When a 300-mL PFOS solution with an initial concentration of 50 mg/L was treated by the discharge with an average power input of 211 W, we found that 85% of PFOS was decomposed after 300 min. Fluorine ion, sulfonate ion, and perfluorocarboxylic acids (PFCAs, C_nF_2n+1COOH, n = 1–7) were generated during the treatment as byproducts. As the energy efficiency was not very high compared with that using plasmas generated within gas bubbles, further optimization of reactor configuration and voltage waveform is needed.

We first present a one-pot synthesis method of well-defined polyhedral gold nanocrystals (AuNCs)/ polyelectrolyte composite film. Well-defined AuNCs were generated during polymerization process of ionic liquids and surfactants to the polyelectrolyte matrix using atmospheric pressure plasmas. Structure of the resulting composite film was characterized using several analysis tools such as scanning electron microscope (SEM) and transmission electron microscope (TEM). The solution remaining after removing the composite film was characterized by ultraviolet-visible (UV-vis) spectroscopy. We found that the composite film contained a large amount of AuNCs which were various polyhedrals including tetrahedron, tetragonal bipyramid, truncated bipyramid, and decahedron. Interestingly, the AuNCs were stereoscopically distributed in the matrix without any agglomeration and size and shape of AuNCs were controlled by changing plasma exposure time and Au precursor concentration. The size of AuNCs decreased along a cross-section of the composite film in the direction from top to bottom. Through systematic investigations, we proposed the formation mechanism of AuNCs/polyelectrolyte composite film through interfacial liquid plasma polymerization. This resulting composite film containing polyhedral AuNCs holds a promise in various applications such as biosensors or plasmonic sensors based on its unique features.

Since recently, silver nanoparticles have attracted a huge interest by the scientific community thanks to their long term and broad-spectrum antimicrobial properties. This has given rise to intense researches on clean, controlled and efficient synthesis routes. Amongst them, liquid phase – pulsed laser ablation (LP-PLA) exhibits highly promising outcomes, allowing a safe, in-situ, tunable production of metallic nanomaterial of high purity. This method consists in focusing a pulsed incident laser beam on a metallic target immersed in a liquid. The interaction between laser and target material create a plasma plume charged of species of the target and the media. This plasma phase has a strong impact on the composition, size and shape of the generated nanostructures. Selecting correct laser parameters like the fluence, the wavelength,… and suitable solvent permit to monitor as well the species in the plasma as the final material
In this paper, the production of silver nanoparticles (Ag NPs) by nanosecond laser ablation in two acrylate monomers, dodecyl acrylate (DOCA) and perfluorodecyl acrylate (PFDA), have been investigated in order to provide a well-controlled nanoparticle/polymer antibacterial materials owning a long term antibacterial effect by adjusting the release of silver ions. Ablation process in high carbon content organic solvent have shown the formation of Ag NPs embedded in graphitic matrix. The influence of the fluence and the number of pulses have been, for the first time, investigated to find trends to better controlled these kind of structures and adjust their bactericidal activity. Based on AAS, Raman, UV-Visible and TEM analysis, the complex mechanisms of silver ablation in monomeric precursor has been elucidated and consists in two steps: i) at low pulses number, the formation of AgNPs included in a graphitic matrix and ii) at higher pulses number, the secondary absorption of laser pulses by the colloids in solution run in the case of DOCA to the modification or removal of the graphite and release or coalescence of the particles depending on the fluence. For the second monomer, PFDA, the matrix formed is so thick that only the graphite species are changed conserving particles size intact.
So this study highlight the potential of this technics to gives colloidal solutions of tuinable Ag NPs in monomer from particles embedded in a matrix or native of diameter of few nanometres to 20 nm.