Low-pressure Dielectric Barrier Discharge Research Articles

Electrode Cooling and Microwave Absorption by Phase Change Fluid Discharge Plasma

It is hard to realize the high microwave absorption property and the low operating temperature in a gas discharge plasma simultaneously, due to the electron number density, and electron neutral collision frequency physically needed for the former is a typical severe heating scenario for the latter. In this article, the phase change process is proposed to be introduced into the controlled area of the discharge plasma system to increase collision frequency and decrease the discharging electrode temperature at the same time. An ac high-voltage power-driven quasi-periodic array of the phase change fluid discharge (PCFD) device is investigated. The most apparent tendency of the PCFD plasma is the improved diffusivity and uniformity. At the same time, the temperature of the electrode and its vicinity, where the phase change material is reserved, is lower than the ambient temperature. Compared with the controlled discharge state of the low gaseous pressure dielectric barrier discharge (L-DBD) plasma without phase change process, the absorption attenuation in the <inline-formula> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula>-band is enhanced in all tested polarization angles, which driving strategy could control. Analyses show that the increased microwave absorption, frequency shift, and bandwidth broadening mainly result from the phase change process and its influences on the plasma discharge.

Low pressure DBD in He-Ne mixture. Spectroscopy of the Afterglow

The paper considers the possibility of using a low-pressure dielectric barrier discharge (DBD) as a plasma source for the active medium of a He-Ne-laser. The results of a spectroscopic study of the decay stage of a DBD plasma of a cylindrical configuration with a pronounced inverse population of the upper level of the 2p55s configuration, which makes the line of 632.8 nm one of the brightest in the visible region of the spectrum, are presented. Based on the analysis of data on the populations of the excited levels of the neon atom and the metastable levels of helium 21S0 and 23S1, it is shown that in the early stage of the DBD afterglow at helium pressures of a fraction of a Torr, the distribution of populations over the 2p55s and 2p54d levels of the neon atom, which is characteristic of the excitation transfer mechanism, is realized. In the late afterglow with the departure of helium atoms He21S0, emission in the visible region of the spectrum is formed mainly by transitions from levels of the 2p53p, configuration, the population of which is associated with He(23S1) atoms. At this stage, the population of the 2p55s and 2p54d states by electron-ion recombination processes is ineffective and does not lead to the formation of population inversion. As an optimal solution in terms of the 632.8 nm line brightness in the afterglow, it is proposed to use a discharge with electrodes along the outer surface of a cylindrical discharge tube, initiated at frequencies that exclude the recombination stage of the afterglow. Keywords: elementary processes, barrier discharge, inverse population, afterglow, helium-neon plasma, excitation transfer

Диэлектрический барьерный разряд в смеси He-Ne низкого давления. Спектроскопия послесвечения

The paper considers the possibility of using a low-pressure dielectric barrier discharge (DBD) as a plasma source for the active medium of a He-Ne laser. The results of a spectroscopic study of the decay stage of a DBD plasma of a cylindrical configuration with a pronounced inverse population of the upper level of the 2p55s configuration, which makes the line of 632.8 nm one of the brightest in the visible region of the spectrum, are presented. It is shown that in the early stage of the DBD afterglow, the distribution of the populations over the 2p55s and 2p54d levels of the neon atom is due to the excitation transfer mechanism Не(21S0) +Ne -- &gt; He(11S0) + Ne*. In the late afterglow with the departure of helium atoms Не(21S0), emission in the visible region of the spectrum is formed mainly by transitions from levels of the 2p53p configuration, the population of which is associated with Не(23S1) atoms. At this stage, the population of the 2p55s and 2p54d states by electron-ion recombination processes is ineffective and does not lead to the formation of population inversion. As an optimal solution in terms of the 632.8 nm line brightness in the afterglow, it is proposed to use a discharge with electrodes along the outer surface of a cylindrical discharge tube, initiated at frequencies that exclude the recombination stage of the afterglow.

The Effect of Low-Pressure Dielectric Barrier Discharge (LPDBD) Plasma in Boosting Germination, Growth, and Nutritional Properties in Wheat

Plasma agriculture is an emerging technology, although the application of non-thermal plasma in wheat productivity is still in its early stage. This study deciphers the effect and mechanistic basis of non-thermal air-generated LPDBD (low-pressure dielectric barrier discharge) plasma in boosting germination, growth and nutritional properties in wheat. Seeds treated with LPDBD plasma exhibited cracked periphery and discernible expansion during seed germination. LPDBD plasma applied for 6 min showed a 22.11% increase in the germination percentage and a substantial increase in iron content in grains compared to non-treated controls. At the cellular level, the concentration of H2O2 in leaves significantly increased (3.56 µM g−1 FW) due to LPDBD treatment compared to controls. This increased level of H2O2 may act as a stimulating agent to trigger the physiological functions in wheat plants. In addition, plants sprouted from air-treated seeds exhibited a marked elevation in CAT and SOD activity accompanied by the increased expression of TaCAT and TaSOD genes in roots of wheat. Interestingly, the grain yield of wheat increased by 27.06% in response to plasma treatment compared to control. Further, grains harvested from plasma-treated plants showed a substantial elevation in iron and fat content as well as decreased moisture content that may contribute to the increased shelf life. The study will open up a new avenue for practical application of plasma in agriculture.

Evaluation of cross-linking and degradation processes occurring at polymer surfaces upon plasma activation via size-exclusion chromatography

Plasma activation is an attractive and widely used technique for the surface modification of polymeric substrates. Despite being extensively explored, the fundamentals of plasma activation processes remain not completely unraveled yet, mainly because of the complex physicochemical changes occurring at the polymer surface. In general, plasma treatment leads to a surface functionalization and/or polymer structure modification. The occurrence of plasma surface functionalization was elaborately studied via X-ray photoelectron spectroscopy (XPS), while the second process was in contrast investigated to a much lower extent. Therefore, this study aims at investigating the relative importance of polymer degradation and cross-linking upon standard plasma treatment conditions via size-exclusion chromatography (SEC). To do so, poly(methyl methacrylate) (PMMA) was subjected to different low and medium pressure dielectric barrier discharge (DBD) plasma treatments sustained in three different gases (Ar, He, N2), and poly(2-ethyl-2-oxazoline) (PEtOx) was treated with Ar plasma at medium pressure. Water contact angle (WCA) measurements were carried out to determine the surface chemistry equilibrium region for Ar plasma treatment at both pressures, after which WCA and XPS measurements were used to evaluate the surface chemistry modification upon the different treatments. The wettability of both PMMA and PEtOx increased for all treatments, which could be linked to the introduction of polar functionalities on the surface, as observed by XPS. By taking into consideration these chemistry changes, all SEC measurements indicated that polymer degradation was the dominant process, while some polymer coupling was observed for Ar plasma treatment at medium pressure. For PMMA treatment at low pressure, a similar degradation was observed for all gases. This was in contrast to the medium pressure treatments for which the Ar plasma induced a more significant chain scission in comparison to N2 and He. This could probably be attributed to the plasma properties, as Ar DBDs at medium pressure are known to consist of highly energetic microdischarges which are typically absent for the other treatments. Additionally, the different degradation behavior of PMMA and PEtOx highlighted the prominent influence of the initial chemical polymer structure on the plasma activation response. As such, this study further establishes the effective use of SEC in the evaluation of polymer degradation and cross-linking upon plasma activation.

Investigation of mechanisms involved in seed germination enhancement, enzymatic activity and seedling growth of rice (Oryza Sativa L.) using LPDBD (Ar+Air) plasma

The study investigates the effect of LPDBD (Low Pressure Dielectric Barrier Discharge) (Ar + Air) plasma on seed germination, seedling growth and antioxidant enzyme activity of rice. Rice seeds were treated with LPDBD (Ar + Air) plasma for 2min, 4min, 6min, 8min and 10min. Seed germination rate, seedling growth, total chlorophyll content, enzymatic activity, total soluble sugar and protein concentration were increased in plants grown from the LPDBD (Ar + Air) plasma treated seeds. It was observed that the sprouting of seeds and the growth of seedlings of rice depends on the feed gases used to generate plasma and plasma processing time. In the case of plantlets germinated from the plasma-treated seeds of rice, the H2O2 level was increased significantly both in leaves and roots for 6min, 8min and 10min treatment respectively. No significant change was observed in Nitric Oxide (NO) concentration in seed, leaf, or root of plants grown from LPDBD (Ar + Air) plasma-treated seeds. The amount of total soluble sugar and protein increased significantly in the case of 2min, 4min, 6min, 8min and 10min seed treatment. Although plants exhibited no significant increase in APX activities, but a significant increase of CAT and SOD activity in the leaf and root was found. This study reveals that LPDBD (Ar + Air) plasma is involved in the elevation of ROS species in leaf and root of rice plants which is tightly regulated by the upregulation of CAT activity that ultimately enhances the seed germination and growth of rice plantlets.

Low-pressure OH radicals reactor generated by dielectric barrier discharge from water vapor

Hydroxyl (OH) radicals were generated by dielectric barrier discharge (DBD) from water vapor in a multi-pass cell with a volume of 8000 cm3. The cell was filled with the following water vapor at reduced pressure. The absolute OH number density was accurately determined by direct absorption spectroscopy using a tunable laser operating at 2.8 μm. The absolute OH number density was around 1012 molecules/cm3. Helium, methane, ethane, propane, and carbon monoxide were respectively introduced into the multi-pass cell to study their influences on the OH number density. The decay rate of OH number density was directly related to the reaction rates of the added gases. The low-pressure DBD OH multi-pass cell can be used as a reactor to further study the reaction kinetics associated with OH radicals.

Efficacy of low pressure DBD plasma in the reduction of T-2 and HT-2 toxin in oat flour

T-2 and its major metabolite HT-2 toxin are naturally occurring contaminants in cereals, with the highest concentrations determined in oats. Because of their toxicity and resistance to conventional methods used in mycotoxin degradation, development of new effective procedures for reduction of T-2/HT-2 toxin levels is needed. The aim of this study was to investigate the effect of different gas types within various timeframes on the efficiency of T-2 and HT-2 toxin degradation by low pressure dielectric barrier discharge (DBD) plasma in oat flour. Although humidity of the sample influences the intensity of the plasma, oxygen atoms efficiently oxidize the sample and produce CO and N2. Before and after treatment, T-2 and HT-2 toxin concentrations were analysed by the confirmatory liquid chromatography tandem-mass spectrometry (LC-MS/MS) method. The highest reduction of T-2 and HT-2 toxin of 43.25% and 38.54%, respectively, was achieved using nitrogen plasma and this proved to be time-dependent.

Effects of Microwave and Cold Plasma Assisted Hydrodistillation on Lemon Peel Oil Extraction

Abstract This study aimed to investigate the effect of low-pressure dielectric barrier discharge (DBD) plasma on microwave-assisted hydrodistillation of lemon peel oil extraction. Microwave pre-treated lemon peel powder was exposed to plasma treatment (1.0, 1.5, 2.0, and 2.5 kV) for 10 min. The treated lemon peel powders were subjected to hydrodistillation to extract the essential oil and the extraction yields were calculated. The extracted oil was analyzed for chemical composition with gas chromatography-mass spectrometry (GC-MS). Effect of plasma on the surface morphology of the lemon peel was observed in a scanning electron microscope (SEM) which revealed the formation of fissures and cracks owing to the higher extraction yield. Plasma treatment at 2.5 kV was observed higher extraction yield than conventional hydrodistillation (149.34 % rise) and the chemical composition of plasma treated sample essential oil remains significantly unchanged. Thus, DBD plasma could be a promising technique to enhance the lemon peel essential oil extraction.

Inactivation of Bacillus subtilis spores on the surface of small spheres using low-pressure dielectric barrier discharge

Inactivation of Bacillus subtilis spores on the surface of small spheres by dielectric barrier discharge (DBD) using relatively low AC high voltage (<10 kV0-p) for practical applications in the sterilization of small dried food was investigated. In this study the 6 and 10 mm gap distances were employed to place small dried foods inside the DBD, but a gap distance of more than 3 mm generally did not generate DBD at this applied voltage and atmospheric pressure. Therefore, the pressure was reduced to generate DBD and the relationship between discharge area rate and pressure was investigated using discharge area rate as the index. Low-pressure DBD (LPDBD) at 6 and 10 mm gap distances showed the maximum discharge area rates of 28% and 25% at 50 and 30 kPa, respectively. After 4 min treatment, B. subtilis spores on the surface of glass beads as the model of a small dried food were inactivated and the survival ratio decreased to 3.6 × 10−4 after the LPDBD treatment at 10 mm gap distance, and no viable cells were detected after the LPDBD treatment at 6 mm gap distance. Moreover, the humidification of the atmosphere was effective in improving the inactivation efficiency of LPDBD treatment, with which, B. subtilis spores were inactivated within 2 min of LPDBD treatment at 6 mm gap distance.

Effects of LPDBD Plasma and Plasma Activated Water on Germination and Growth in Rapeseed (Brassica napus)

The study deals with the effect of low pressure dielectric barrier discharge (LPDBD) plasma and plasma activated water (PAW) produced with Ar, O2 and Air on germination and growth in rapeseed. Although H2O2 concentration showed no significant changes, α‑amylase activity (germination inducer) significantly increased in seeds due to LPDBD plasma. In addition, the activity of SOD and CAT was significantly induced in seeds of rapeseed treated with PAW. Rapeseed plants grown from the LPDBD plasma treated seeds showed significant improvements in shoot characteristics, chlorophyll synthesis, total soluble protein and sugar concentration compared to controls. Interestingly, plasma treated plants also showed no significant variations of H2O2 in tissue(s) which is supported by the biochemical and molecular evidence(s) of antioxidant enzymes. Plants exhibited a significant increase in tissue APX and CAT activities along with BnAPX and BnCAT expression(s) in roots when seeds were treated with LPDBD Air/O2 and PAW O2. This suggests that LPDBD plasma might have been involved with elevated level of reactive oxygen species, which was tightly controlled through the upregulation of APX and CAT activities and thus trigger the growth and development in rapeseed plants. These findings reveal the role and mechanisms of LPDBD technique facilitating germination and growth in rapeseed plants.

Phase-resolved optical emission spectroscopy of a transient plasma created by a low-pressure dielectric barrier discharge jet

A transient plasma created by a low-pressure dielectric-barrier discharge operated with argon was investigated by means of optical emission spectroscopy and imaging. Images of the discharge and emission spectra were recorded with sub-phase resolution and relative densities of excited argon states were obtained. Profiles of densities and electron temperatures were evaluated for the discharge cycle by comparison with results of a collisional-radiative model (CRM). To overcome difficulties in sub-cycle modelling of the important argon 1s states, a combination of the CRM with a density estimation based on radiation-trapping is proposed. Absolute densities of all four 1s states were measured and additionally verified by tunable laser absorption spectroscopy. The presented combination may help to improve optical diagnostics of rare gas plasmas in cases were the dominating processes for the 1s states are not known with sufficient accuracy.

Mechanisms and Signaling Associated with LPDBD Plasma Mediated Growth Improvement in Wheat

This study investigates the effect and mechanisms of low pressure dielectric barrier discharge (LPDBD) produced with Ar/O2 and Ar/Air technique causing biological stimulation leading to improved germination and growth in wheat. Both plasma treatments caused rougher and chapped seed surface along with noticeable improvement in seed germination in wheat. Beside this, seed H2O2 concentration significantly increased compared to controls subjected to Ar/O2 and Ar/Air while this phenomenon was more pronounced due to Ar/Air plasma. Analysis of plants grown from the plasma treated seeds showed significant improvement in shoot characteristics, iron concentration, total soluble protein and sugar concentration in comparison with the controls more efficiently due to Ar/O2 plasma than that of Ar/Air. Further, none of the plasma treatments caused membrane damage or cell death in root and shoot of wheat. Interestingly, Ar/O2 treated plants showed a significant increase (2-fold) of H2O2 compared to controls in both root and shoot, while Ar/Air plasma caused no changes in H2O2. This phenomenon was supported by the biochemical and molecular evidence of SOD, APX and CAT in wheat plants. Plants derived from Ar/O2 treated seeds demonstrated a significant increase in SOD activity and TaSOD expression in roots of wheat, while APX and CAT activities along with TaCAT and TaAPX expression showed no significant changes. In contrast, Ar/Air plasma caused a significant increase only in APX activity in the shoot. This suggests that Ar/O2 plasma caused a slight induction in H2O2 accumulation without triggering the H2O2 scavengers (APX and CAT) and thus, efficiency affect growth and development in wheat plants. Further, grafting of control and Ar/O2 treated plants showed a significant increase in shoot biomass and H2O2 concentration in grafts having Ar/O2 rootstock regardless of the type scion attached to it. It indicates that signal driving Ar/O2 plasma mediated growth improvement in wheat is possibly originated in roots. Taken together, this paper delivers new insight into the mechanistic basis for growth improvement by LPDBD technique.

Fast enhancement on hydrophobicity of poplar wood surface using low-pressure dielectric barrier discharges (DBD) plasma

The hydrophilicity of woody products leads to deformation and cracks, which greatly limits its applications. Low-pressure dielectric barrier discharge (DBD) plasma using hexamethyldisiloxane was applied in poplar wood surface to enhance the hydrophobicity. The chemical properties, micro-morphology, and contact angles of poplar wood surface before and after plasma treatment were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDX), atomic force microscopy (AFM), and optical contact angle measurement (OCA). Moreover, tinfoil film was used as the base to reveal the enhancement mechanism. The results showed that hexamethyldisiloxane monomer is first broken into several fragments with active sites and hydrophobic chemical groups. Meanwhile, plasma treatment results in the formation of free radicals and active sites in the poplar wood surface. Then, the fragments are reacted with free radicals and incorporated into the active sites to form a network structure based on the linkages of Si-O-Si and SiOC. Plasma treatment also leads to the formation of acicular nano-structure in poplar wood surface. These facts synergistically enhance the hydrophobicity of poplar wood surface, demonstrating the dramatically increase in the equilibrium contact angle by 330%.

In vitro killing of mycobacteria by low temperature atmospheric pressure plasma and dielectric barrier discharge plasma for treatment of tuberculosis

BackgroundTo prove the efficacy of cold atmospheric plasma (CAP) to inactivate mycobacteria in vitro, we tested the susceptibility of important mycobacterial species to evaluate potential alternative treatment options. MethodsWe tested 8 different mycobacterial species M. tuberculosis22MTB: Mycobacterium tuberculosis. (MTB) (resistant against isoniazid (INH)), M. marinum, M. ulcerans, M. abscessus, M. chelonae, M. africanum, M. terrae and M. avium against two typical CAP devices, a low temperature atmospheric pressure plasma jet (APPJ) and a dielectric barrier discharge plasma (DBD). The tests followed a modified standard procedure by comparing obtained inhibition zones after irradiation of 3, 15, 30 and 60s on selective (Löwenstein-Jensen) medium. ResultsIrradiation by both sources proved high antimycobacterial killing effectiveness against all species including the INH-resistant strain of M. tuberculosis and a set of most important mycobacterial pathogens causing mycobacteriosis. Plasma irradiation <t=60s resulted in significant microbiocidal reduction of mycobacteria of the MTBC-complex and important nontuberculous mycobacteria (NTM) in vitro. DBD and APPJ plasma killed all isolates on Löwenstein-Jensen medium. ConclusionPlasma treatment (both sources) may serve as a future option for treatment of skin tuberculosis evolved from M. tuberculosis (lupus vulgaris), NTM and leprosy and also for surface decontamination after suspected contact with acid fast microbes.

Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl4/O2/N2 Gas Mixtures

Low-pressure dielectric barrier discharge (DBD) TiCl4/O2 and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15°. Compared to titanium oxide films deposited in TiCl4/O2 gas mixtures, those in TiCl4/O2/N2 gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2 gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20°, while that of undoped titanium oxide films is larger than 64° when they are measured after one week. The low-pressure TiCl4/O2 plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film's fragmentation due to the over-high film stress. Optical emission spectra (OES) of TiCl4/O2 DBD plasmas at various power supply driving frequencies are presented.

Dry plasma synthesis of graphene oxide–Ag nanocomposites: A simple and green approach

A room temperature dry reduction approach, i.e., a low pressure dielectric barrier discharge (DBD) plasma jet, was presented to synthesize highly dispersed graphene oxide-based Ag nanoparticles. TEM, EDS, XRD and XPS tests were used for the characterization of the as-prepared nanocomposites. By comparing the Ag nanoparticles prepared by the DBD plasma jet with and without hydrogen plasma pretreatment, it was found that the latter were highly monodispersed with a uniform size of around 2nm and deposited on the surface of the graphene oxide as a form of face-centered cubic structure, and it also showed a better antibacterial activity against Escherichia coli, which may be due to the smaller particle size, larger surface area and more beneficial dispersity of Ag nanoparticles.

Development of a Portable Mass Spectrometer Characterized by Discontinuous Sample Gas Introduction, a Low-Pressure Dielectric Barrier Discharge Ionization Source, and a Vacuumed Headspace Technique

The present study has attempted to downscale a mass spectrometer in order to make it portable and enable onsite analysis with it. The development of a small mass spectrometer required the use of a compact pump whose displacement was small, decreasing the sensitivity of that spectrometer. To get high sensitivity with a small mass spectrometer, we have integrated novel techniques: a highly sensitive ionization source and efficient extraction of sample vapor. The low-pressure dielectric barrier discharge ionization (LP-DBDI) source made it possible to increase the conductance between the source and the mass analyzer, compared with ambient ionization sources, enhancing the efficiency of the ion transfer from the ionization source to the mass analyzer. We have also developed a vacuumed headspace method efficiently transporting the sample vapor to the ionization source. The sensitivity was further enhanced by also using a discontinuous sample gas introduction technique. A prototype portable mass spectrometer using those novel techniques was found to be sensitive enough to detect 0.1 ppm methamphetamine, 1 ppm amphetamine, 1 ppm 3,4-methylenedioxymethamphetamine, and 10 ppm cocaine in liquid.

Sensitive low‐pressure dielectric barrier discharge ion source

We developed a novel highly sensitive soft ionization method: a low-pressure dielectric barrier discharge ionization (LP-DBDI) source. In this configuration, samples pass through the inside of a dielectric barrier discharge (DBD). Since samples pass through a DBD and its plasma jet, high ionization efficiency is expected. Furthermore, high transmission efficiency from the ion source to the mass spectrometer is also expected since the ion source is placed in a vacuum. Mass spectrometric detection was carried out in positive ion mode using an ion trap mass spectrometer. The LP-DBDI source or a conventional atmospheric pressure chemical ionization (APCI) source was attached to the mass spectrometer. Samples were vaporized and sent to ion sources with air flowing at a constant flow rate of 1.5 L/min. The LP-DBDI source was compared with a conventional APCI source. Mass spectra of methyl salicylate, 2-undecanone and methamphetamine were acquired using the LP-DBDI source. Protonated molecules were mainly observed in the mass spectra. The sensitivities for methyl salicylate and 2-undecanone obtained using the LP-DBDI source were 44 times and 39 times higher, respectively, than those obtained using an APCI source. LP-DBDI is a soft ionization method characterized by only minor fragmentation, similar to APCI. The sensitivity of the LP-DBDI source was found to be about 40 times higher than that of the conventional APCI source.

Comparison of low and atmospheric pressure air plasma treatment of polyethylene

Surface activation of polyethylene (PE) samples has been carried out using low pressure plasmas (at two different operating frequencies, namely, 40 kHz and 13·56 MHz) and dielectric barrier discharge (DBD) (50 Hz frequency and at atmospheric pressure), and the results are compared. The surface of the PE samples has been exposed to these different plasmas for various time durations ranging from 1 to 30 min. The treated samples have also been studied for their aging behaviour by exposing them to the ambient atmosphere for up to 7 days. The plasma induced morphological changes were studied using an scanning electron microscope and an atomic force microscope, while the formation of various functional groups was identified using Fourier transform infrared analysis. The surface energy values were observed to increase from 27·5 dyne cm−1 (of untreated PE) to 73·8 and 52·2 dyne cm−1 after low pressure 40 kHz and 13·56 MHz air plasma treatment respectively and to 35·6 dyne cm−1 after the DBD air plasma treatment. The low pressure plasma treatment at an operating frequency of 40 kHz has produced the best results in the surface activation of PE. During the aging process, the formation of C = C bonds was observed on the surface of PE.