A study on the antimicrobial efficacy of RF oxygen plasma and neem extract treated cotton fabrics

The paper deals with a thorough investigation on the antimicrobial activity of RF oxygen plasma and Azadirachtin (neem extract) treated cotton fabric. The hydrophilicity of cotton fabric was found to improve when treated with RF oxygen plasma. The process parameters such as electrode gap, time of exposure and oxygen pressure have been varied to study their effect on improving the hydrophilicity of the cotton fabric. The static immersion test has been carried out to assess the hydrophilicity of the oxygen plasma treated samples and the process parameters were optimized based on these test results. The formation of carbonyl group during surface modification in the plasma treated sample was analysed using FTIR studies. The surface morphology has been studied using SEM micrographs.The antimicrobial activity was imparted to the RF oxygen plasma treated samples using methanolic extract of neem leaves containing Azadirachtin. The antimicrobial activity of these samples has been analysed and compared with the activity of the cotton fabric treated with neem extract alone. The investigation reveals that the surface modification due to RF oxygen plasma was found to increase the hydrophilicity and hence the antimicrobial activity of the cotton fabric when treated with Azadirachtin.     

Effect of dichlorodimethylsilane on plasma-treated cotton fabric

Cotton fabric was treated with dichlorodimethylsilane (DCDMS) solution by two methods. In the first method, the fabrics were directly dipped into DCDMS solution for different time intervals and in the second method, the fabric was first subjected to radiofrequency (RF) plasma treatment for different durations and optimized exposure power condition and then immersed in DCDMS solution. The physical properties of cotton fabrics, treated with DCDMS in the presence/absence of air plasma have been compared with those of the control fabrics. Changes in the surface morphology structure and composition were observed through scanning electron microscopy and attenuated total reflectance-IR. The change in colour parameters of the fabric due to the treatment was assessed by Dataflash 100 colour measurement spectrophotometer with colourtools QC 1.3 colour quality software. The water repellent property of untreated and modified fabrics was studied using AATCC test method 39 (1971). The effectiveness of the water repellent property was checked by washing the treated fabrics up to ten cycles. Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

Plasma treatment of polyester fabric to impart the water repellency property

Polyester fabric is treated with DCDMS solution by two methods: dipping the fabric directly in DCDMS solution for different intervals and dipping the fabric in DCDMS solution after its exposure into RF plasma chamber for different durations at optimized exposure power conditions. The physical properties of polyester fabric treated with DCDMS in the presence or absence of air plasma have been compared with control fabric. Different characterization techniques like scanning electron microscope, attenuated total reflectance-IR and Dataflash 100 colour measurement spectrophotometer are used to assess the surface morphology, composition and change in colour parameters. Water repellency property of both untreated and modified polyester fabric is studied using AATCC test method 39 (1971). The effectiveness of the water repellency property of modified polyester fabric is checked by repeated washing up to ten cycles. This article was presented at the Second International Conference on the Frontiers of Plasma Physics and Technology, 21–25 February 2005, Goa, India.     

Morphological alterations in salivary glands of Rhipicephalus sanguineus ticks (Acari: Ixodidae) exposed to neem seed oil with known azadirachtin concentration

Neem (Azadirachta indica) has attracted the attention of researchers worldwide due to its repellent properties and recognized effects on the morphology and physiology of arthropods, including ticks. Therefore, this study aimed to demonstrate the effects of neem seed oil enriched with azadirachtin on salivary glands of Rhipicephalus sanguineus ticks, targets of great veterinary interest because of their ability to transmit pathogens to dogs. For this, R. sanguineus semi-engorged females were subjected to treatment with neem seed oil, with known azadirachtin concentrations (200, 400 and 600 ppm). After dissection, salivary glands were collected and evaluated through morphological techniques in light microscopy, confocal scanning laser microscopy and transmission electron microscopy, so that the possible relation between neem action and further impairment in these ectoparasites feed performance could be established. Neem oil demonstrated a clear dose-dependent effect in the analyzed samples. The agranular (type I) and granular acini (types II and III) showed, particularly in individuals treated with the highest concentrations of the product, cells with irregular shape, intense cytoplasmic disorganization and vacuolation, dilation of rough endoplasmic reticulum lumen, besides alterations in mitochondrial intermembrane space. These morphological damages may indicate modifications in salivary glands physiology, demonstrating the harmful effects of compounds present in neem oil on ticks. These results reinforce the potential of neem as an alternative method for controlling R. sanguineus ticks, instead of synthetic acaricides.     

GaAs半导体表面的等离子氮钝化特性研究

采用射频(RF)等离子方法,对Ga As样品进行了150 W高功率等离子氮钝化及快速退火处理。经过该方法钝化后的样品,光致发光(PL)强度上升了91%。XPS分析得出,Ga As样品表面的氮化效果随着氮等离子体功率的增加而逐渐趋于明显。氮化后的样品表面未发现氧化物残余。样品在空气中加热放置30 d,PL强度下降不明显,说明表面钝化层具有良好的稳定性。     

Experimental and statistical analysis of dielectric barrier discharge plasma effect on sonochemically TiO2 coated cotton fabric using complete composite design

A single step ultrasonic biosynthesis method was used to synthesize and coat TiO₂ nanoparticles onto DBD plasma functionalized raw cotton. Titanium isopropoxide was reduced with aloe vera plant extract into TiO₂ nanoparticles. The effect of DBD plasma treatment on self-cleaning property of TiO₂ coated fabric was optimized statistically by using a complete composite design. To induce functional groups on the cotton fabric surface, the fabric was pre-treated with DBD plasma over various periods of time. The plasma exposure time, molarity of solution and ultrasonication time were optimized using complete composite design package. TiO₂ nanoparticles revealed spherical shape and anatase phase with average crystallite size of 10.46 nm. The statistically optimized plasma exposure time, molarity and sonication time was 7 min, 0.80 and 75 min, respectively. The plasma activation of fabric significantly improved the adsorption, tensile strength and self-cleaning ability of TiO₂ coated fabric.     

Helium/oxygen atmospheric pressure plasma jet treatment for hydrophilicity improvement of grey cotton knitted fabric

The influence of atmospheric pressure plasma jet (APPJ) treatment on the hydrophilicity of grey cotton knitted fabric (GCKF) was investigated. For comparison, specimens which had undergone different treatments were tested by contact angle measurement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), fourier-transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) and X-ray diffraction (XRD). The results imply that helium/oxygen APPJ could improve the hydrophilicity of GCKF by modifying the surface properties. In addition, combining dewaxing processes with He/O₂ APPJ treatment was found to tremendously improve the hydrophilicity of GCKF. The mechanism of this was also confirmed by Ruthenium Red staining which showed most of pectic substances inside the cotton fiber existed beneath the waxy layer and on top of the cellulose microfibril.     

纺织纤维及其制品非破坏性快速鉴别的研究

纺织纤维的快速鉴别对我国纺织品生产过程质量控制、贸易和市场监督具有重要实际意义。文章收集了的12种纺织纤维共214个样品,研究了各种形态样品的近红外光谱测量方法。采用多元光散射校正方法消除噪声和基线漂移对光谱的影响。对样品总集光谱进行系统树分析,发现组成接近的纤维样本能均够聚类在一起,有些不同种类纤维之间有交叠。结合近红外光谱和簇类的独立软模式方法(SIMCA),可以实现化学组成非常接近的不同纤维种类的区分。该研究结果表明,采用近红外分析技术,实现非破坏性地快速鉴别纺织纤维是可行的。     

基于近红外光谱和变量优选的棉麻混纺织物棉含量快速检测

纺织品纤维成分的快速检测对其生产过程质量监控、贸易和市场监督均具有重要的意义。利用近红外光谱技术联合变量优选对棉麻混纺织物中的棉含量进行快速检测研究。采用NIRFlex N-500型傅里叶近红外光谱仪在4 000～10 000 cm-1光谱范围内采集样本的反射光谱,对样本光谱进行范围初选和预处理分析。在此基础上,利用UVE(uninformative variables elimination),SPA(successive projections algorithm)及CARS (competitive adaptive reweighted sampling)方法对光谱变量进行优选,再应用PLS(partial least squares)建立棉麻混纺织物中的棉含量预测模型。最后,采用最优预测模型对未参与建模的样本进行预测。研究结果表明,4 052～8 000 cm-1光谱范围为棉含量较优的建模光谱范围。CARS变量选择方法能较为有效地提高预测模型的精度,CARS-PLS模型的校正集、预测集相关系数和均方根误差分别为0.903,0.749和8.01%,12.93%。因此,近红外光谱联合CARS变量优选可以用于棉麻混纺织物棉含量的快速检测,CARS方法可以有效简化预测模型,提高预测模型性能。     

等离子体处理的聚丙烯和聚乙烯的粘合体

采用射频辉光放电等离子体和介质阻挡放电等离子体对聚丙烯（PP）和聚乙烯（PE）进行处理后,使用聚氨酯进行粘接,并测试了混合粘合体的剪切强度。介质阻挡放电功率是100 W时,等离子体处理对混合粘合体的剪切强度无影响。介质阻挡放电的功率为200 W、处理时间20 s时,等离子体处理效果最佳,剪切强度为1.58 MPa,是未处理的混合粘合体的14.36倍。介质阻挡放电的功率是300 W时,样品在10 s内就被击穿。射频辉光放电等离子体中,使用空气处理后最大剪切强度为1.60 MPa（100 W,3 min）,使用氮气处理后的最大剪切强度为1.57 MPa（200 W,3 min）。通过扫描电镜（SEM）对等离子体处理前后的PP表面形貌观察,发现未处理样品的表面比较平滑,而经等离子体放电处理后的样品表面变得疏松,出现了大量泡状物质,表面粗糙程度提高。     

Effect of Low-Pressure Radio Frequency Plasma on Knitted Fabrics Made of Natural Cellulose Fibers

The effect nonequilibrium low-temperature plasma has on knitted fabric made of natural cellulose fibers is considered. It is shown that plasma treatment improves the hydrophilicity of the material and can replace the liquid preparation of knitted fabrics for dyeing.     

Surface physical-morphological and chemical changes leading to performance enhancement of atmospheric pressure plasma treated polyester fabrics for inkjet printing

Without any preprocessing, polyester fabric has lower ability to hold on water due to the smooth morphology and chemistry property of polyester fibers. Therefore, patterns directly printed with pigment inks have poor color yields and easily bleed. In this paper, atmospheric pressure plasma was used to pretreat polyester fabric in order to provide an active surface for the inkjet printing. The results showed that surface-modified polyester fabrics could obtain the effects of features with enhanced color yields and excellent pattern sharpness. SEM images indicated that the rough surface of plasma treated fibers could provide more capacities for the fabric to capture inks and also facilitate the penetration of colorant particles into the polyester fabric. XPS analysis revealed that air + 50%Ar plasma introduced more oxygen-containing groups onto the fabric surface than air plasma. Although AFM images indicated that etching effects generated by air plasma treatments were more evident, the air/Ar plasma treated sample has higher K/S value and better color performance. These studies have also shown that the chemical modification of plasma appears to be relatively more significant for improving the effect of inkjet printing.     

Structural and optical properties of amorphous hydrogenated silicon carbonitride films produced by PECVD

Amorphous hydrogenated silicon carbonitride thin films (a-Si:C:N:H), deposited by plasma enhanced chemical vapour deposition (PECVD) using hexamethyldisilazane (HMDSN) as monomer and Ar as feed gas, have been investigated for their structural and optical properties as a function of the deposition RF plasma power, in the range of 100-300 W. The films have been analysed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), UV-vis-NIR spectrophotometry and atomic force microscopy (AFM). From the analysis of the FT-IR spectra it results that the films become more amorphous and inorganic as RF plasma power increases. The incorporation of oxygen in the deposited layers, mainly due to the atmospheric attack, has been evaluated by XPS and FT-IR spectroscopy. Reflectance/transmittance spectra, acquired in the range of 200-2500 nm, allow to descrive the film absorption edge for interband transitions. A relationship between the optical energy band gap, deduced from the absorption coefficient curve, and the deposition RF plasma power has been investigated. The reduction of the optical energy gap from 3.85 to 3.69 eV and the broadening of the optical absorption tail with RF plasma power increasing from 100 to 300 W are ascribed to the growth of structural disorder, while the increase of the refractive index, evaluated at 630 nm, is attributed to a slight densification of the film. The AFM analysis confirms the amorphous character of the films and shows how the deposited layers become rougher when RF plasma power increases. The wettability of the film has been studied and related to the chemical composition and to the morphology of the deposited layers.     

Surface morphology changes of poly(ethyleneterephthalate) fabrics induced by cold plasma treatments

Some selective cold plasma processing modify specific surface properties of textile polymeric materials such as their dyeability, wettability and hydrorepellence. To correlate the sample surface changes with the acquired surface properties allows one to obtain information on the chemical and physical processing involved in plasma treatment. In this work, atomic force microscopy (AFM) has been applied to investigate the morphological and topographical surface modifications induced by RF cold plasma processing of poly(ethyleneterephthalate) (PET) fabrics. Rms surface roughness and surface area of the samples are measured before and after the treatments. The morphology changes have been analysed as a function of the treatment time and air gas pressure. Measurements have been performed also using plasmas produced by different gases such as He, Ar, SF₆ and CF₄. The PET shows different behaviour with different gas plasmas. In the case of air, He and Ar gases the sample surface modifications seem to be mainly due to etching effects, while the fluorine atoms grafting probably is responsible for surface rearrangement process using SF₆ and CF₄ gases. As a consequence different surface properties are produced in the plasma treated samples. Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

Influence of argon/oxygen atmospheric dielectric barrier discharge treatment on desizing and scouring of poly (vinyl alcohol) on cotton fabrics

The effect of argon/oxygen atmospheric dielectric barrier discharge (DBD) treatment on desizing and scouring of polyvinyl alcohol (PVA) on cotton fabric was studied with respect to the treatment duration of 1, 2, 4 and 6 min. X-ray photoelectron spectroscopy (XPS) analysis indicated that oxygen concentration increased for the plasma treated PVA film. Solubility measurement revealed that plasma treatment increased PVA solubility in hot washing but less effective in cold washing. Scanning electron microscopy (SEM) showed that the fiber surfaces were as clean as unsized fibers after 6 min treatment followed by hot washing. Wickability analysis indicated that the capillary heights of plasma treated fabrics increased significantly as the plasma treatment duration increased. The results of the yarn tensile strength test showed that the plasma treatment did not have a negative effect on fabric tensile strength.     

Effect of rf cold plasmas on polysaccharides

Low temperature-low pressure argon, nitrogen, and air plasmas generated with rf radiation have been used to treat cotton cellulose and other saccharides. The physical and chemical nature of each substrate was altered by the cold plasma. Although no gross topographical changes of the cotton surface were visible even under the electron microscope, plasma-treated cotton wetted more rapidly and more uniformly than its control, and other saccharides were more soluble in water and other chemical reagents (such as ammonium hydroxide) after plasma treatment. Free radicals were created within the cellulose matrix and structures of all other saccharides. ESR signals, which indicate presence of carbon radicals, degenerated asymmetrically, implying that other types of radicals also existed. ESCA spectra of cotton cellulose showed that some carbon atoms had been oxidized and some oxygen atoms reduced during plasma activation. Activated cottons displayed chemiluminescence and had redox powers that varied with their environments. When cotton and organic monomers were simultaneously present in cold plasma, reactive centers initiated polymerization ofthin films upon the cotton surface. Plasmaactivated cottons exhibited the same chemical reactions as a-hydroxyperoxides or their precursors from living organisms.     

Functionalization of PET and PA6.6 woven fabrics

In the present work as received woven fabrics of polyethylene terephthalate (PET) and polyamide 6.6 (PA6.6) were exposed to a continuous dielectric barrier discharge (DBD), in air at atmospheric pressure, at selected discharge power values and conveyor speeds. The chemical modification of the fabric surface was studied by contact angle analysis, attenuated total reflection (ATR)-FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). The results confirmed that the treatment changed the fabric surface chemistry, increasing its wettability by polar liquids and its oxygen content. Contact angle results showed different behaviour of the two polymer fabrics toward ageing effects; while PET showed a contact angle increase along the subsequent days of treatment, the PA6.6 fabric maintained its hydrophilicity even 15 days after treatment. The surface morphology analysed by scanning electron microscopy (SEM), did not show any significant difference before and after treatment.     

ADBD plasma surface treatment of PES fabric sheets

Plasma treatment of textile fabrics is investigated as an alternative to the environmentally hazardous wet chemical fabric treatment and pretreatment processes. Plasma treatment usually results in modification of the uppermost atomic layers of a material surface and leaves the bulk characteristics unaffected. It may result in desirable surface modifications, e.g. surface etching, surface activation, cross-linking, chain scission and oxidation. Presented paper contains results of the applicability study of the atmospheric pressure dielectric discharge (ADBD), i.e. dielectric barrier discharge sustaining in air at atmospheric pressure and ambient temperature for synchronous treatment of several sheets of fabric. For tests sheets of polyester fabric were used. Effectivity of the modification process was determined with hydrophilicity measurements evaluated by means of the drop test. Hydrophilicity of individual sheets of fabric has distinctly increased after plasma treatment. Plasma induced surface changes of textiles were also proven by identification of new functional groups at the modified polyester fabric surface. Existence of new functional groups was detected by ESCA scans. For verification of surface changes we also applied high-resolution microphotography. It has shown distinct variation of the textile surface after plasma treatment. Important aspect for practical application of the plasma treatment is the modification effect time-stability, i.e. time stability of acquired surface changes of the fabric. The recovery of hydrophobicity was fastest in first days after treatment, later gradually diminished until reached almost original untreated state.     

Ultrasound irradiation based in-situ synthesis of star-like Tragacanth gum/zinc oxide nanoparticles on cotton fabric

Application of natural biopolymers for green and safe synthesis of zinc oxide nanoparticles on the textiles is a novel and interesting approach. The present study offers the use of natural biopolymer, Tragacanth gum, as the reducing, stabilizing and binding agent for in-situ synthesis of zinc oxide nanoparticles on the cotton fabric. Ultrasonic irradiation leads to clean and easy synthesis of zinc oxide nanoparticles in short-time at low-temperature. FESEM/EDX, XRD, FT-IR spectroscopy, DSC, photocatalytic activities and antimicrobial assay are used to characterize Tragacanth gum/zinc oxide nanoparticles coated cotton fabric. The analysis confirmed synthesis of star-like zinc oxide nanoparticles with hexagonal wurtzite structure on the cotton fabric with the average particle size of 62 nm. The finished cotton fabric showed a good photocatalytic activity on degradation of methylene blue and 100% antimicrobial properties with inhibition zone of 3.3 ± 0.1, 3.1 ± 0.1 and 3.0 ± 0.1 mm against Staphylococcus aureus, Escherichia coli and Candida albicans.     

激光大气等离子体光谱特性实验研究

报道了对波长为1．06μm的脉冲激光在气体样品中产生的等离子体进行光谱研究的结果。气体样品为一个标准大气压的纯氮、纯氧和空气,光谱探测范围为300～900nm。结果表明,各种气体样品的激光等离子体光谱均表现为连续谱和线状谱的叠加,文中分别给出了连续谱和线状谱的基本特征,讨论了这些特征与等离子体物理特性的关系,并分析了纯氮、纯氧与空气激光等离子体光谱之间的异同。给出了激光等离子体光谱的时间演化和空间分布的基本特征,并初步讨论了与这些特征相关的等离子体物理特性。这些结果有助于加深对激光等离子体特性和机理,特别是对等离子体产生后的弛豫过程和复合机制的了解。