Low-temperature Plasma Treatment Research Articles

Effects of low-temperature plasma, microwave and 60Co γ-irradiation treatments on the flavor characteristics of lychee whole fruit powder

Powdering whole lychee fruit is one of the most effective methods for improving the comprehensive utilization rate of lychees. In this study, lychee whole fruit powder (LWFP) was prepared and treated with low-temperature plasma, microwave, and 60Co γ-irradiation treatments to enhance its quality. Volatile organic compounds (VOCs) were analyzed using Headspace Solid Phase Micro-extraction Gas Chromatography-mass Spectrometry (HS-SPME-GC-MS), Headspace Gas Chromatography Ion Mobility Spectrometry (HS-GC-IMS), and electronic nose (E-nose) techniques. Electronic tongue (E-tongue) analysis revealed that both sweetness and bitterness were significant taste indicators of LWFP. GC-MS analysis revealed that the predominant volatile compounds in LWFP were terpenoids and alcohols, specifically nerol, geraniol, ɑ-pinene, hexylbenzene, ɑ-caryophyllene, caryophyllene oxide, and isoamylenol. GC-IMS identified small-molecule aldehydes such as 2-methyl propanal, hexanal, propanal, and 2-methylbutanal as significant contributors to the aroma profile. Moreover, key aromatic contributors include dimethyl sulfide, 1-penten-3-one, and acetic acid. Notably, microwave treatment exerted the most significant effect on the aroma profile of lychee. In contrast, low-temperature plasma and irradiation treatments exhibited similar and consistent changes. Specifically, microwave treatment primarily increased the concentration of larger terpenoid molecules such as nerol, 1-phenylhexane, and caryophyllene oxide, whereas low-temperature plasma and irradiation had a greater impact on smaller aldehyde molecules such as hexanal and 2-methylbutanal. All treatments enriched the sweet fruity, brilliant woody, and cabbage scents of LWFP.

Exploring the efficacy of in-vitro low-temperature plasma treatment on single and multispecies dental cariogenic biofilms

The primary aim of this study was to investigate the impact of treatment with low-temperature plasma (LTP) for varying exposure durations on a multispecies cariogenic biofilm comprising C. albicans, L. casei, and S. mutans, as well as on single-species biofilms of L. casei and C. albicans, cultured on hydroxyapatite discs. Biofilms were treated with LTP-argon at a 10 mm distance for 30 s, 60 s, and 120 s. Chlorhexidine solution (0.12%) and NaCl (0.89%) were used as positive (PC) and negative controls (NC), respectively. Argon flow only was also used as gas flow control (F). Colony-forming units (CFU) recovery and confocal laser scanning microscopy (CLSM) were used to analyze biofilm viability. LTP starting at 30 s of application significantly reduced the viability of multispecies biofilms by more than 2 log10 in all treated samples (p < 0.0001). For single-species biofilms, L. casei showed a significant reduction compared to PC and NC of over 1 log10 at all exposure times (p < 0.0001). In the case of C. albicans biofilms, LTP treatment compared to PC and NC resulted in a significant decrease in bacterial counts when applied for 60 and 120 s (1.55 and 1.90 log10 CFU/mL, respectively) (p < 0.0001). A significant effect (p ≤ 0.05) of LTP in single-species biofilms was observed to start at 60 s of LTP application compared to F, suggesting a time-dependent effect of LTP for the single-species biofilms of C. albicans and L. casei. LTP is a potential mechanism in treating dental caries by being an effective anti-biofilm therapy of both single and multispecies cariogenic biofilms.

Biomechanical surface roughness analysis of ramie-low melt polyester nonwovens exposed to plasma

This study aims to characterize ramie-low melt polyester nonwoven fabrics treated with low-temperature plasma and to analyze 3-D images based on object-depth mapping (ODM) using the MATLAB® R2022a software. We examined the low-temperature plasma treatment of nonwoven ramie fabrics using a plasma generator with 30 kV output power, six-minute treatment times, and a 4.5 cm distance between electrodes. The fabric’s chemical properties and surface topography were investigated using scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). An analysis of the SEM images was performed using a statistical approach and image processing to determine the level of surface roughness. FTIR analysis revealed that fabrics exposed for six minutes differed from those that were not. Our findings indicated that plasma treatment caused the following: 1) Ramie fabrics to become more hydrophilic, as shown by their increased T% in the FTIR of hydrophilic functional groups such as hydroxyl (O-H), carboxyl (-COOH), and carbonyl (C=O); 2) A higher surface roughness was observed in nonwoven fabric during SEM testing and image processing; 3) Plasma treatment of fabrics resulted in a higher coefficient of variation (CV) than untreated fabrics; 4) Nonwoven fabric mass reduction. Based on this study, we found the relationship between plasma-treated ramie fabric and textiles in biomechanics. Plasma treatment reduced the mass of ramie fabric by 0.11 %, according to our findings. We found that the greater the mass reduction, the greater the surface roughness value. The novelty of this study is the use of 3-D images based on object-depth mapping (ODM) using the MATLAB® R2022a software in SEM to observe surface roughness to the physical properties of ramie fabric for the first time.

Impact of plasma-modified pretreatment on the tensile properties of carbon fiber-reinforced epoxy composites

Abstract Low-temperature jet plasma modification technology is a surface treatment method designed to enhance the surface properties of materials without causing severe thermal damage. This technique modifies surface characteristics by creating plasma and utilizing ions and reactive groups within the plasma to chemically interact with the material’s surface. In this study, surface modification of carbon fibers was carried out by using low-temperature jet mixed oxygen plasma technology at treatment speeds of 25 mm/s, 50 mm/s, 100 mm/s, and 200 mm/s. Following the modification process, carbon fiber-reinforced epoxy composites were fabricated by using a hand-lay-up technique. Subsequently, the tensile properties of the carbon fiber composites were tested to evaluate the impact of the plasma treatment on their mechanical performance. The experimental results demonstrated a significant enhancement in the tensile properties of the composites when the carbon fibers were pretreated at a rate of 50 mm/s. This enhancement was evidenced by an impressive increase of 82.38% in tensile strength and 30.96% in tensile modulus compared to untreated samples. This signifies that low-temperature plasma treatment has a beneficial effect on enhancing the surface properties of carbon fibers and improving the performance of composites. This finding provides substantial support for the extensive application of carbon fiber composites.

Cold Nitrogen Plasma: A Groundbreaking Eco-Friendly Technique for the Surface Modification of Activated Carbon Aimed at Elevating Its Carbon Dioxide Adsorption Capacity

The commercially available activated carbon was modified using barrier and spark discharge low-temperature nitrogen plasma treatment. The samples were investigated using nitrogen sorption at a temperature of −196 °C, XRD, SEM, and FTIR methods, and elemental analysis. The nitrogen content on the surface was increased, but other properties, such as specific surface area, total pore volume, pseudocrystallite height, and pseudocrystallite width, remained unchanged. The activated carbons after nitrogen plasma treatment indicated higher CO2 adsorption than the pristine ones. Since the investigated materials only differed in their nitrogen content, it has been unequivocally demonstrated that the increased presence of nitrogen is responsible for the enhanced adsorption of CO2. The low-temperature nitrogen plasma treatment of activated carbon is a promising method for enhancing CO2 capture.

Plasma-induced surface interactions of Pd/SrTiO3 catalyst for improved performance of photocatalytic degradation of toluene

Defective engineering and the addition of noble metal are effective strategies to realize the high photocatalytic performance of SrTiO3 perovskite. Here, the Pd/SrTiO3 catalyst was successfully prepared by the low-temperature plasma treatment coupling with photochemical deposition of metal Pd, which was applied to the photocatalytic degradation of toluene. Compared with single STO, STON, and Pd-STO catalysts, the prepared Pd-STON catalyst shows the excellent UV photocatalytic performance toward toluene degradation, realizing a ca.80 % degradation efficiency within 90 min reaction time. Based on various characterizations, it revealed that plasma treatment promoted the formation of surface oxygen defects, and strengthened the metal-support interaction. The resultant surface oxygen vacancy accelerated the migration rate of photogenerated electrons and the separation of electrons and holes in space, benefiting for superior performance. It is expected that this study can provide new avenues for the rational design of highly efficient photocatalysts for potential practical applications.

Structure and Properties of Bioactive Titanium Dioxide Surface Layers Produced on NiTi Shape Memory Alloy in Low-Temperature Plasma.

The NiTi alloy, known for its shape memory and superelasticity, is increasingly used in medicine. However, its high nickel content requires enhanced biocompatibility for long-term implants. Low-temperature plasma treatments under glow-discharge conditions can improve surface properties without compromising mechanical integrity. This study explores the surface modification of a NiTi alloy by oxidizing it in low-temperature plasma. We examine the impact of process temperatures and sample preparation (mechanical grinding and polishing) on the structure of the produced titanium oxide layers. Surface properties, including topography, morphology, chemical composition, and bioactivity, were analyzed using TEM, SEM, EDS, and an optical profilometer. Bioactivity was assessed through the deposition of calcium phosphate in simulated body fluid (SBF). The low-temperature plasma oxidization produced titanium dioxide layers (29-55 nm thick) with a predominantly nanocrystalline rutile structure. Layer thickness increased with extended processing time and higher temperatures (up to 390 °C), though the relationship was not linear. Higher temperatures led to thicker layers with more precipitates and inhomogeneities. The oxidized layers showed increased bioactivity after 14 and 30 days in SBF. Low-temperature plasma oxidation produces bioactive titanium oxide layers on NiTi alloys, with a structure and properties that can be tuned through process parameters. This method could enhance the biocompatibility of NiTi alloys for medical implants.

Deposition of a polymer thin film on a silver surface for surface plasmon sensing

We report a deposition method of a polymer thin film on the silver surface of a surface plasmon sensor for preventing sensitivity degradation in refractive index measurements due to the poor chemical stability of the silver. The deposition of a poly(methyl methacrylate) thin film with a ∼15 nm thickness was conducted by employing a spin coating technique along with a hydrophilicity enhancement of the silver surface using an atmospheric low-temperature plasma treatment. We experimentally verified the thickness by measuring the propagation constant of the surface plasmon. The measured propagation constants that showed the standard deviation at the order of 10−4 indicated microscopical uniformity. Furthermore, the reproducibility of thickness was experimentally verified.

Enhanced Hydrogen Generation through Low-Temperature Plasma Treatment of Waste Aluminum for Hydrolysis Reaction.

This study investigates the low-temperature hydrogen plasma treatment approach for the improvement of hydrogen generation through waste aluminum (Al) reactions with water and electricity generation via proton-exchange membrane fuel cell (PEM FC). Waste Al scraps were subjected to ball milling and treated using two different low-temperature plasma regimes: Diode and magnetron-initiated plasma treatment. Hydrolysis experiments were conducted using powders with different treatments, varying molarities, and reaction temperatures to assess hydrogen generation, reaction kinetics, and activation energy. The results indicate that magnetron-initiated plasma treatment significantly enhances the hydrolysis reaction kinetics compared to untreated powders or those treated with diode-generated plasma. Analysis of chemical bonds revealed that magnetron-initiated hydrogen plasma treatment takes advantage by promoting a dual procedure: Surface cleaning and Al nanocluster deposition on top of Al powders. Moreover, it was modeled that such H2 plasma could penetrate up to 150 Å depth. Meanwhile, electricity generation tests demonstrate that only 0.2 g of treated Al powder can generate approximately 1 V for over 300 s under a constant 2.5 Ω load and 1.5 V for 2700 s with a spinning fan.

Low-Temperature Plasma Pretreatment Enhanced Cholesterol Detection in Brain by Desorption Electrospray Ionization-Mass Spectrometry Imaging.

Cholesterol is a primary lipid molecule in the brain that contains one-fourth of the total body cholesterol. Abnormal cholesterol homeostasis is associated with neurodegenerative disorders. Mass spectrometry imaging (MSI) technique is a powerful tool for studying lipidomics and metabolomics. Among the MSI techniques, desorption electrospray ionization-MSI (DESI-MSI) has been used advantageously to study brain lipidomics due to its soft and ambient ionization nature. However, brain cholesterol is poorly ionized. To this end, we have developed a new method for detecting brain cholesterol by DESI-MSI using low-temperature plasma (LTP) pretreatment as an ionization enhancement. In this method, the brain sections were treated with LTP for 1 and 2 min prior to DESI-MSI analyses. Interestingly, the MS signal intensity of cholesterol (at m/z 369.35 [M + H - H2O]+) was more than 2-fold higher in the 1 min LTP-treated brain section compared to the untreated section. In addition, we detected cholesterol, more specifically excluding isomers by targeted-DESI-MSI in multiple reaction monitoring (MRM) mode and similar results were observed: the signal intensity of each cholesterol transition (m/z 369.4 → 95.1, 109.1, 135.1, 147.1, and 161.1) was increased by more than 2-fold due to 1 min LTP treatment. Cholesterol showed characteristic distributions in the fiber tract region, including the corpus callosum and anterior commissure, anterior part of the brain where LTP markedly (p < 0.001) enhanced the cholesterol intensity. In addition, the distributions of some unknown analytes were exclusively detected in the LTP-treated section. Our study revealed LTP pretreatment as a potential strategy to ionize molecules that show poor ionization efficiency in the MSI technique.

Performance enhancement of Ge/Si avalanche photodetector by specific sidewall passivation using remote oxygen plasma treatment

We report an obvious improvement in the performance of a separated absorption charger-layer multiplication Ge/Si avalanche photodetector, achieved by passivating the sidewalls with a low-temperature remote oxygen plasma (ROP) treatment. The dangling bonds on the Ge surface can be efficiently passivated by the formation of an ideal Ge/GeO2 interface. With ROP passivation, the leakage current of the device shows a three- to fourfold decrease at 300 K, resulting in a dark current (I dark) of 3.5 × 10−6 A at 90% avalanche voltage (V br) and 3.4 × 10−7 A at punch-through voltage (V puhch-through) for the 26 μm-diameter device. A reduction of over tenfold is demonstrated at 200 K and the passivation mechanism is revealed. In addition, a multiplication gain of 94 is obtained under 1550 nm illumination. The device with ROP passivation shows an improved gain bandwidth product of 190 GHz. The enhanced high-frequency response of the device with ROP passivation can be attributed to the alleviation of the retarding effect caused by the interface state on the sidewalls. Without using a trans-impedance amplifier, an opening eye diagram at 28 Gbps is demonstrated, indicating reliable device transmission performance.

An analysis of ramie fiber (Boehmeria nivea L. Gaud) treated with low temperature plasma using a mathematical model

This research aims to characterize low-temperature plasma-treated ramie fibers (Boehmeria nivea L. Gaud), create a mathematical model, and analyze them using image processing. The effects of low-temperature plasma treatment on ramie fibers were investigated using 30 kV output powers, 4-min treatment times, and a 4 cm electrode distance. SEM and FT-IR spectroscopy were used to investigate various aspects of the ramie fiber’s chemical properties and surface topography. This study used a statistical approach to analyze the SEM images. The statistical analysis was used to investigate the surface roughness using the SEM images. FT-IR analysis discovered that fibers that were exposed for four minutes differed from untreated fibers. According to the findings, plasma treatment caused: (1) ramie fiber became more hydrophilic, as indicated by the presence of hydrophilic functional groups such as hydroxyl (O–H), carboxyl (O–C), and carbonyl (C=O) in FT-IR with a deeper T%, (2) ramie fiber mass reduction was accompanied by an increase in surface roughness via SEM testing and image processing, and (3) plasma-treated fiber had a coefficient of mass variation (CV) of 0.7211 higher than untreated fiber. The novelty of this study is the use of image processing in SEM to observe surface roughness and its relationship to the chemical structure of ramie fibers observed with FT-IR. Another novelty of this research is the mathematical model of the interaction of plasma species with the ramie fibers on the plane electrode for the first time.

Modeling of low-temperature plasma inhibition and mechanism of Aspergillus flavus on corn kernels surface

ABSTRACT This study was conducted to optimize a process of low-temperature plasma treatment for the decontamination of Aspergillus flavus (A. flavus) on corn kernels. Impacts of plasma-treated time (30, 60, 90 s), plasma-treated power (300, 400, 500 W), and vacuum degree (85, 90, 95 Pa) on the decontamination effect in this process were explored. The optimal conditions included vacuum degree at 90 Pa, plasma treating time of 90 s, and plasma treating power of 500 W, under which the A. flavus spores was 4.03 log (cfu/g). Plasma treatment triggered antioxidative defense system, broke cell structures, and dispersed cell contents. A large number of free radicals act on lipids and proteins, and malondialdehyde (MDA) accumulate in large quantities, further leading to damage to cell structures.

Ferroelectric memory devices using hafnium aluminum oxides and remote plasma-treated electrodes for sustainable energy-efficient electronics

In this work, we adopt a low-temperature sustainable plasma treatment approach for the fabrication of ferroelectric memory devices. From our experimental results, we found that the ferroelectric polarization characteristics of HfAlOx ferroelectric device could be further improved by using low-temperature nitrogen plasma treatment on bottom TiN electrode for surface modification. The low-temperature nitrogen plasma treatment on TiN bottom electrode not only prevent electrode oxidation, but also lowers the generation of defect traps at the interface between ferroelectric HfAlOx and TiN bottom electrode during high-temperature ferroelectric annealing process. Besides, the nitrogen-treated bottom electrode also can improve bias-stress induced instability and cycling endurance of HfAlOx ferroelectric devices due to the effective suppression of randomly distributed defect traps or oxygen vacancies near the surface of bottom electrode.

Effects of the application of low-temperature atmospheric plasma on titanium implants on wound healing in peri-implant connective tissue in rats

PurposeThis study aimed to clarify the effects of surface modification of titanium (Ti) implants by low-temperature atmospheric pressure plasma treatment on wound healing and cell attachment for biological sealing in peri-implant soft tissue.MethodsHydrophilization to a Ti disk using a handheld low-temperature atmospheric pressure plasma device was evaluated by a contact angle test and compared with an untreated group. In in vivo experiments, plasma-treated pure Ti implants using a handheld plasma device (experimental group: PL) and untreated implants (control group: Cont) were placed into the rat upper molar socket, and samples were harvested at 3, 7 and 14 days after surgery. Histological evaluation was performed to assess biological sealing, collagen- and cell adhesion-related gene expression by reverse transcription quantitative polymerase chain reaction, collagen fiber detection by Picrosirius Red staining, and immunohistochemistry for integrins.ResultsIn in vivo experiments, increased width of the peri-implant connective tissue (PICT) and suppression of epithelial down growth was observed in PL compared with Cont. In addition, high gene expression of types I and XII collagen at 7 days and acceleration of collagen maturation was recognized in PL. Strong immunoreaction of integrin α2, α5, and β1 was observed at the implant contact area of PICT in PL.ConclusionsThe handheld low-temperature atmospheric pressure plasma device provided hydrophilicity on the Ti surface and maintained the width of the contact area of PICT to the implant surface as a result of accelerated collagen maturation and fibroblast adhesion, compared to no plasma application.

Effects of plasma treatment on biodegradation of natural and synthetic fibers

This study investigates the application of plasma treatment as a means to enhance biodegradation and modify the structural characteristics of fibrous composites. The methodological component of the study includes the selection of the research object; production of composites; low-temperature plasma treatment, and treatment of biodegradability and mechanical strength of samples. The strengthening of fibers with cellulose leads to a significant improvement in mechanical strength. Such an indicator as mechanical strength increases from 18 to 21 MPa. Treatment of natural fibers with low-temperature plasma led to an increase in mechanical strength from 18 to 25 MPa. Treating reinforced fibers with low-temperature plasma currently results in an even greater enhancement in mechanical strength, increasing from 18 to 29 MPa.The electron microscopy of samples reveals some differences in cell wall microfibrils between plasma-treated and non-treated samples. The non-treated fibres are found to have chips and voids. Meantime, the plasma-treated fibres show structural changes in certain regions which resemble wood charring. Through a comprehensive analysis, this research underscores the substantial impact of plasma treatment on the degradation kinetics and morphological features of cellulose-based composites. The results reveal distinct alterations in the composition and behavior of plasma-treated fibres, signifying a shift towards enhanced biodegradability. The natural fibres examined in this study contained 28–30% lignin, whereas the composites exhibited a lower lignin content of 21–23%. These findings corroborate the inference that plasma treatment induces significant changes in fibre structure, accelerating the biodegradation process by 7 days.

Effect of Low-Temperature Oxygen Plasma Treatment of Titanium Alloy Surface on Tannic Acid Coating Deposition.

In this study, the effect of low-temperature oxygen plasma treatment with various powers of a titanium alloy surface on the structural and morphological properties of a substrate and the deposition of a tannic acid coating was investigated. The surface characteristics of the titanium alloy were evaluated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Following this, the tannic acid coatings were deposited on the titanium alloy substrates and the structural and morphological properties of the tannic acid coatings deposited were subject to characterization by XPS, SEM, and spectroscopic ellipsometry (SE) measurements. The results show that the low-temperature oxygen plasma treatment of titanium alloys leads to the formation of titanium dioxides that contain -OH groups on the surface being accompanied by a reduction in carbon, which imparts hydrophilicity to the titanium substrate, and the effect increases with the applied plasma power. The performed titanium alloy substrate modification translates into the quality of the deposited tannic acid coating standing out by higher uniformity of the coating, lower number of defects indicating delamination or incomplete bonding of the coating with the substrate, lower number of cracks, thinner cracks, and higher thickness of the tannic acid coatings compared to the non-treated titanium alloy substrate. A similar effect is observed as the applied plasma power increases.

Oxygen plasma treatment-enhanced humidity sensing performance of MoS2 nanoparticles-anchored nitrogen-doped laser-induced graphene

The monitoring of humidity has elicited considerable interest in diverse fields. Nevertheless, the intricate nature of preparatory procedures employed for humidity sensors poses a formidable challenge in the pursuit of a streamlined, expeditious, and highly efficient technique for fabricating humidity-sensitive materials. Herein, the fundamental formation principle of polyimide (PI) film serves as the underpinning for the application of a swift and effective laser direct writing technique in creating a composite integrating MoS2 nanoparticles anchored within nitrogen-doped laser-induced graphene (MoS2@NLIG). Subsequently, a rapid low-temperature oxygen plasma treatment is administered to enhance humidity sensing capabilities of the MoS2@NLIG composite. The oxygen plasma treatment-enhanced MoS2@NLIG humidity sensor exhibits exceptional capability in detecting relative humidity (RH) with a significant sensitivity of 61,219.97 Ω/%RH across an extensive range from 11% to 95%RH, while maintaining a hysteresis as minimal as 3.72%. Moreover, the sensor exhibits outstanding response and recovery times with respective values of 9 s and 15.5 s. Additionally, the humidity sensor demonstrates the capacity to identify human exhalation, potentially serving as a valuable electronic device for monitoring clinical respiration.

Sputtering-grown undoped GeSn/Ge multiple quantum wells on n-Ge for low-cost visible/shortwave infrared dual-band photodetection

Multispectral photodetectors (PDs) operating in visible (VIS) to shortwave infrared (SWIR) wavelength ranges are highly desired for various civil and military applications. Traditional vertical p-i-n SWIR PDs lack the detection ability for VIS light due to photon dissipation in the neutral regions. Herein, an i-n type PD was proposed and demonstrated with sputtering-grown undoped Ge0.92Sn0.08/Ge multiple quantum wells (MQWs) on n-Ge substrate to realize VIS/SWIR dual-band detection from 400 to 2000 nm. Three response peaks resulted from the resonate cavity effect at 430, 660 and 1530 nm, respectively, were observed. Benefiting from the defect-free coherent GeSn/Ge MQWs and low-temperature surface plasma treatment, a remarkably low bulk leakage current density of 5.9 mA/cm2 and a low surface leakage current of 37.5 μA/cm were achieved at room temperature under −1 V, resulting in an ultralow dark current density of 13.36 mA/cm2 for a 200-μm-diameter PD. Temperature-dependent electrical characterizations revealed that the dark current was ideally dominated by carrier diffusion mechanism. Eminent detectivities of 5.2 × 108, 7.1 × 108 and 5.6 × 109 Jones at 410, 660 and 1530 nm, respectively, under −1 V were achieved simultaneously at room temperature. This work provides a path way for fabricating low-cost, VIS/SWIR dual-band PDs with complementary metal–oxide–semiconductor (CMOS) compatible technology.

In-Situ FTIR and Laser Induced Fluorescence RONS Characterization of Atmospheric Pressure Nanosecond-Pulsed Surface DBD Plasma for Indirect Treatments of E. Coli

We study the bactericidal efficacy of surface dielectric barrier discharge low-temperature plasma treatments, powered by nanosecond high voltage pulses. We achieve ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim $$\\end{document}4-log reduction in Escherichia coli population, after 10 min treatments, at a distance of 1.5 cm from the plasma surface. To investigate the reactive oxygen and nitrogen species (RONS) responsible for the bactericidal effect, we employ in-situ fourier transform infrared (FTIR) spectroscopy to measure a selection of relevant species, such as O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}, NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_5$$\\end{document}. The measurements are taken under various relative humidity conditions to replicate the bacteria treatment environment. While RONS originating from nitrogen chemistry are detected, nitric oxide (NO), a pivotal molecule in nitrate production, is absent due to the sensitivity limitations of FTIR detection. To overcome this limitation, we employ laser induced fluorescence utilizing a picosecond-pulsed laser to measure the kinetics of NO produced by the plasma. Our results show that the NO concentration is smaller than 1 ppm and primarily localized near the plasma surface, with concentrations increasing proportionally with relative humidity. Notably, at a distance of 1.5 cm from the plasma surface, at which the E. coli is treated, the concentration of NO falls below 50 ppb. Although NO is pivotal in generating secondary reactive species within the plasma, our results suggest that it does not directly contribute to the bacteria inactivation process. Instead, other molecules, such as O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}, NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}, and N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O, which are found in higher concentrations, may be responsible for the bactericidal properties observed in indirect plasma treatments.