Aqueous Solution‐Processable,Flexible Thin‐Film Transistors Based on Crosslinked Chitosan Dielectric Thin Films

The hydrophilic character of chitosan (CS) limits its use as a gate dielectric material in thin‐film transistors (TFTs) based on aqueous solution‐processable semiconductor materials. In this study, this drawback is overcome through controlled crosslinking of CS and report, for the first time, its application to aqueous solution‐processable TFTs. In comparison to natural CS thin films, crosslinked chitosan (Cr‐CS) thin films are hydrophobic. The dielectric properties of Cr‐CS thin films are explored through fabrication of metal–insulator–metal devices on a flexible substrate. Compared to natural CS, the Cr‐CS dielectric thin films show enhanced environmental and water stabilities, with a high breakdown voltage (10 V) and low leakage current (0.02 nA). The compatibility of Cr‐CS dielectric thin films with aqueous solution‐processable semiconductors is demonstrated by growing ZnO nanorods via a hydrothermal method to fabricate flexible TFT devices. The ZnO nanorod‐based TFTs show a high field‐effect mobility (linear regime) of 10.48 cm² V^?1 s^?1. Low temperature processing conditions (below 100 °C) and water as the solvent are utilized to ensure the process is environmental friendly to address the e‐waste problem.     

Preparation and characterization of antimicrobial films based on nanocrystalline cellulose

Nanocrystalline cellulose (NCC) has great potential in applications in medical and food packaging due to its abundance, high specific surface area, biodegradability, biocompatibility, and reproducibility. N-Halamine is one of the most effective antibacterial agents, with broad-spectrum efficacy against microorganisms, good stability, and reproducibility. Due to the nanosize effect and high specific surface area of NCC, N-halamine-modified NCC is potentially an excellent biocidal compound. In this paper, an N-halamine precursor 1-hydroxymethyl-5,5-dimethylhydantoin (HDH) was used to modify NCC with cyanuric chloride (cych) as the bonding agent. After chlorination, the produced NCC-cych-HDH-Cl became antibacterial. The synthesized NCC-cych-HDH-Cl was added to a chitosan (CS) and polyvinyl alcohol (PVA) solution to prepare antibacterial films. The optimum mixing ratio of PVA and CS in the PVA/CS films and concentration of NCC-cych-HDH-Cl were investigated. The surface morphologies and mechanical properties of the antibacterial films were characterized with scanning electron microscopy, transmission electron microscopy, and mechanical strength tests. The results indicated that the film with 90/10 PVA/CS and 7.0% loading of NCC-cych-HDH-Cl exhibited excellent tensile strength. The antibacterial film with 5.91 × 10¹⁷ atoms/cm² of active chlorine displayed an excellent antibacterial property against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47101.     

Structures,morphological control,and antibacterial performance of tungsten oxide thin films

The present work describes structural, morphological, and antibacterial properties of thin film coatings based on tungsten oxide material on stainless-steel substrates. Thin films were prepared by RF magnetron sputtering of W targets in the oxygen/argon plasma environment in 60 W sputtering power. The characterization of the specimens was made on the basis of microstructure and antibacterial properties of the thin films surface. The effect of O₂/Ar ratio on the structure, morphology, and antibacterial properties of the tungsten oxide thin films was studied. Methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier Transform Infrared Spectroscopy (FTIR) were used to assess the properties of deposited thin films. XRD peak analysis indicates (100) and (200) of WO₃ phase with hexagonal structure. Moreover, the micro-strain, grain size, and dislocation density were obtained. It is noteworthy that by increasing the oxygen percentage from 10% to 20%, the grain size decreases from 81 to 23 nm while the film micro-strain and dislocation density increases. The SEM results illustrates that tungsten oxide thin films are made of interconnected nano-points in a chain shape with sphere-shaped grains with diameter variation from 10 to 100 nm. The FTIR spectra displays four distinct bands corresponds to O–W–O bending modes of vibrations and W–O–W stretching modes of the WO₃ films. The antibacterial effects of tungsten oxide thin films on steel stainless substrate against Escherichia coli bacteria are also examined for the first time and our observation shows that the number of bacteria on all tungsten oxide samples decreases after 24 h. The samples exhibit an excellent antibacterial performance. This paper renders a strategy through which the tungsten oxide thin films for antibacterial purpose and proposes that WO₃ thin films are ideal for various medical applications including stainless steel medical tools, optical coatings, and antibacterial coatings.     

Construction of Chlorine Labeled ZnO–Chitosan Loaded Cellulose Nanofibrils Film with Quick Antibacterial Performance and Prominent UV Stability

In this study, novel “green” and highly stable biocidal materials composed of cellulose nanofibrils (CNF) and ZnO–chitosan (ZnO–CS) hybrids are constructed by combing vacuum filtration and heat‐press processing without the use of any organic solvent. CNF/ZnO–CS films are soaked in a 10% sodium hypochlorite aqueous solution to endow antibacterial activity. The chlorinated CNF/ZnO–CS samples and chlorinated CNF/ZnO‐CS (CNF/ZnO‐CS‐Cl) possess quick antimicrobial activity against Staphylococcus aureus and Escherichia coli within 30 min of contact compared with CNF and CNF/ZnO–CS controls. The addition of ZnO endows the films with remarkable UV light stability. After exposure to a UV chamber for 24 h, the chlorine loadings on the prepared samples decrease to 0.13%, where 76% of the chlorine loss can be regained after rechlorination. Furthermore, cytotoxicity evaluations reveal the feasibility of the films for in vitro applications. The prepared rechargeable CNF/ZnO–CS–Cl films will have many promising antibacterial applications.     

改性纤维素和壳聚糖共混膜的制备及性能研究

将水溶性的纤维素衍生物——羟乙基纤维素与壳聚糖乙酸水溶液用溶液浇铸法制得羟乙基纤维素/壳聚糖(HEC/CS)共混膜。确定了该共混膜的最佳制备条件,并测试了其力学性能和生物降解性能。结果表明:HEC/CS共混膜具有好的抗菌性。     

Antibacterial activity of DLC and Ag–DLC films produced by PECVD technique

Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to its potential application as surface coatings on biomedical devices. Doped carbon films are also useful as biomaterials. As silver (Ag) is known to be a potent antibacterial agent, Ag–DLC films have been suggested to be potentially useful in biomedical applications. In this paper, DLC films were growth on 316L stainless steel substrates by using Plasma Enhanced Chemical Vapour Deposition (PECVD) technique with a thin amorphous silicon interlayer. Silver colloidal solution was produced by eletrodeposition of silver electrodes in distilled water and during the deposition process it was sprayed among each 25 nm thickness layer DLC film. The antibacterial activity of DLC, Ag–DLC and silver colloidal solution were evaluated by bacterial eradication tests with Escherichia coli (E. coli) at different incubation times. With the increase of silver nanoparticle layers in Ag–DLC, the total compressive stress decreased significantly. Raman spectra showed the film structure did not suffer any substantial change due to the incorporation of silver. The only alteration suffered was a slightly reduction in hardness. DLC and Ag–DLC films demonstrated good results against E. coli, meaning that DLC and Ag–DLC can be useful to produce coatings with antibacterial properties for biomedical industry.     

Preparation and characterization of antimicrobial PVA hybrid films with N‐halamine modified chitosan nanospheres

Chitosan is a promising candidate as an antimicrobial agent in food packaging materials and biomaterials due to its biocompatibility, biodegradability, non‐toxicity and biocidal activity. In this study, chitosan derivatives, α‐(5,5‐dimethyl hydantoin amino)‐chitosan (CS‐HDH), were synthesized. The CS‐HDH nanospheres were prepared by ionic gelation method and characterized by SEM, FT‐IR, XRD, and TGA‐DTG. The prepared novel chitosan nanospheres in the range of 200–300 nm had good dispersibility. The CS‐HDH nanospheres were used to prepare antibacterial PVA hybrid films by solvent evaporation technique. The surface morphology and thermal property of hybrid films were measured by SEM, AFM, and TGA‐DTG. The results of antibacterial test showed that the hybrid film with 1.24 × 10¹⁸ atoms/cm² of active chlorine exhibited excellent antibacterial properties against Staphylococcus aureus and Escherichia coli O157:H7, and all of bacteria could be inactivated within 5 min. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44204.     

Properties of different chitosan/low‐density polyethylene antibacterial plastics

A series of low‐density polyethylene (LDPE) antibacterial functional plastics were prepared by mechanical blending with commercial chitosan (CS), self‐made water‐soluble chitosan (W‐CS), and microchitosan as antibacterial agents. The effects of the antibacterial agent content on the elongation at break of the obtained plastics were tested, and the bacteriostatic effects against Escherichia coli, Bacillus subtilis, and Proteus species were investigated. The results indicate that the elongation at break of LDPE with antibacterial agent decreased and had a slower decline when the mass ratio of CS to LDPE was greater than 0.5 : 100. The LDPE‐based plastics showed different antibacterial activities against the three experimental strains, and plastics with W‐CS exhibited the best antibacterial activity against B. subtilis. However, the antibacterial content had little effect on the antibacterial ratio. Moreover, 6‐week soil burial tests indicated that the addition of CS caused a decrease in the resistance of LDPE to microbiological deterioration in a natural environment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fabrication and characterization of chitosan/poly(vinyl alcohol) electrospun nanofibrous membranes containing silver nanoparticles for antibacterial water filtration

Electrospun nanofibrous membranes (ENMs) were fabricated based on chitosan/poly(vinyl alcohol) (CS/PVA) with a 70/30 mass ratio containing silver nanoparticles (AgNPs) via the electrospinning method. AgNPs were produced on the surface of CS/PVA nanofibers by adding AgNO₃ to a CS/PVA blend solution as a silver rendering component. The presence of AgNPs in the polymer blend solution was detected by UV spectrophotometry. The morphology of nanofibers before and after cross-linking with glutaraldehyde was investigated by the field emission scanning electron microscopy. The formation and size distribution of AgNPs onto the surface of nanofibers were observed by transmission electron microscopy and confirmed by energy dispersing X-ray spectroscopy. As-spun and cross-linked CS/PVA nanofibers revealed a smooth surface with diameters ranging from 58 to 73 nm and 95 to 109 nm, respectively. The effect of AgNP formation on the chemical structure of nanofibers was explored by Fourier transform infrared spectroscopy. Static and dynamic antibacterial filtration efficiencies of CS/PVA ENMs, containing differing amounts of AgNO₃, have been tested against Escherichia coli, a gram negative bacterium. The antibacterial assessment results exhibited a significant increase in both static and dynamic antibacterial filtration efficiencies of the prepared CS/PVA ENMs by addition of AgNO₃ as a bactericidal agent.     

Preparation of aminated poly (L-lactic acid) film coated with multilayers of mussel-inspired heparin-like carboxymethylcellulose sodium and chitosan for anticoagulant materials

In this study, dopamine hydrochloride was grafted onto the sulfated carboxymethylcellulose sodium with different sulfated degree (DA-g-SCMC_S) as heparin-like polysaccharides. By studying the preliminary structure and coagulation time of DA-g-SCMC_S, the DA-g-SCMC2 possessing good anticoagulant properties were selected to be assembled layer by layer on the surface of aminated poly (L-lactic acid) (APLLA) film with chitosan (CS). The characterization properties including morphologies and wettability of DA-g-SCMC2/CS multilayers modified APLLA films were studied by scanning electron microscope and water contact angle instrument. Anticoagulation tests revealed that the (DA-g-SCMC2/CS)₁₅ multilayers modified APLLA film experienced a decrease of 37.5% and 73.68% in the adsorption of bovine serum albumin (BSA) and fibrinogen (FBG), respectively. And the platelet adhesion ability was reduced by 92.42% compared with the APLLA film. The degree of platelet activation (PF4 and TAT) and hemolysis rates of modified APLLA films also decreased significantly. Besides, the modified APLLA films promoted the growth of L929 cells and exhibited remarkable anti-inflammatory and antibacterial abilities. To summarize, the APLLA films modified with heparin-like multifunctional DA-g-SCMC2/CS multilayers exhibit outstanding biocompatibility, cytocompatibility, anti-inflammatory, and antibacterial characteristics, showcasing their potential as anticoagulation materials.     

An antibacterial coating based on a polymer/sol-gel hybrid matrix loaded with silver nanoparticles

In this work a novel antibacterial surface composed of an organic-inorganic hybrid matrix of tetraorthosilicate and a polyelectrolyte is presented. A precursor solution of tetraethoxysilane (TEOS) and poly(acrylic acid sodium salt) (PAA) was prepared and subsequently thin films were fabricated by the dip-coating technique using glass slides as substrates. This hybrid matrix coating is further loaded with silver nanoparticles using an in situ synthesis route. The morphology and composition of the coatings have been studied using UV-VIS spectroscopy and atomic force microscopy (AFM). Energy dispersive X-ray (EDX) was also used to confirm the presence of the resulting silver nanoparticles within the thin films. Finally the coatings have been tested in bacterial cultures of genus Lactobacillus plantarum to observe their antibacterial properties. It has been experimentally demonstrated that these silver loaded organic-inorganic hybrid films have a very good antimicrobial behavior against this type of bacteria.     

Controlling the morphological,structural, and optical properties of one-dimensional PCDTBT nanotubes by template wetting

In this study, the synthesis of poly [N-9′-heptadecanyl-2, 7-carbazole-alt-5, 5-(4′, 7′-di-2-thienyl-2′, 1′, 3′-benzothiadiazole)] (PCDTBT) nanotubes via a templating method is reported. PCDTBT nanotubes were successfully grown by immersing the porous alumina template into 15 mg/ml of solution concentration for 2- and 24-h periods and annealed at 50°C. Changes in morphological and optical properties between nanotubes of different infiltration times (2 and 24 h) as well as its thin films are observed. The longer infiltration time of 24 h produced nanotubes with enhanced morphological, structural, and optical properties. Nanotubes that are formed between 2 and 24 h of infiltration show enhancement in absorption, photoluminescence, and shift in Raman peak if compared to their thin films.     

Effects of Excess Bismuth Content in Precursor Solutions on Ferroelectric Properties of BiFeO3 Thin Films Prepared by a Chemical Solution Deposition

Cr-substituted BiFeO₃ (BFCr) thin films prepared from precursor solutions with stoichiometric composition and various excess Bi contents ranged from 5 to 20 mol% were fabricated on Pt/TiO₂/SiO₂/Si(100) substrates by a chemical solution deposition method, and the effects of excess Bi content in precursor solutions on the ferroelectric properties of the as-deposited BFCr thin films were studied. It was found that the BFCr thin film prepared from precursor solution with excess Bi content of 5 mol% exhibited the best dielectric constant-frequency and polarization-electric field characteristics. In detail, its dielectric constant is 158 at frequency of 100 kHz and remnant polarization (P_r) value is 49 μ C/cm² at electric field of 600 kV/cm.     

Effect of Annealing Temperature on the Optical Spectra of CdS Thin Films Deposited at Low Solution Concentrations by Chemical Bath Deposition (CBD) Technique

Two different concentrations of CdCl(2) and (NH(2))(2)CS were used to prepare CdS thin films, to be deposited on glass substrate by chemical bath deposition (CBD) technique. CdCl(2) (0.000312 M and 0.000625 M) was employed as a source of Cd(2+) while (NH(2))(2)CS (0.00125 M and 0.000625 M) for S(2-) at a constant bath temperature of 70 °C. Adhesion of the deposited films was found to be very good for all the solution concentrations of both reagents. The films were air-annealed at a temperature between 200 °C to 360 °C for one hour. The minimum thickness was observed to be 33.6 nm for film annealed at 320 °C. XRD analyses reveal that the films were cubic along with peaks of hexagonal phase for all film samples. The crystallite size of the films decreased from 41.4 nm to 7.4 nm with the increase of annealing temperature for the CdCl(2) (0.000312 M). Optical energy band gap (E(g)), Urbach energy (E(u)) and absorption coefficient (α) have been calculated from the transmission spectral data. These parameters have been discussed as a function of annealing temperature and solution concentration. The best transmission (about 97%) was obtained for the air-annealed films at higher temperature at CdCl(2) (0.000312 M).     

Physically crosslinked polyvinyl alcohol/chitosan/gum tragacanth hydrogels loaded with vitamin E for wound healing applications

For the healing process, in this study, an innovative polymeric hydrogel network including polyvinyl alcohol (PVA)/chitosan (CS)/gum tragacanth (GT) loaded with vitamin E (VE) was produced by the freeze–thaw approach. In order to investigate the characteristics of the prepared samples, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) analyzes were performed. Also, water vapor transmission rate (WVTR), swelling ratio, gel fraction and mechanical properties were measured. Then, to observe their cytocompatibility, MTT assay and cell adhesion studies were assessed. The results of FTIR confirmed the presence of PVA, CS, GT, and VE in hydrogel films. As well as, the SEM images showed the effect of the freezing and thawing method in creating a smooth surface with small and regular pores. It was found with adding the CS and GT to PVA improves swelling ratio, gel fraction, WVTR and elongation of hydrogel films. Further, in examining the adhesion and cytotoxicity of the samples, the non-toxic quiddity of the PVA/CS/GT hydrogel films was corroborated. In the end, the antibacterial properties revealed that the film containing GT and CS had the greatest antibacterial activity. According to the observed results, PVA/CS/GT hydrogel films loaded with VE can be good for wound healing applications.     

Synthesis of ordered mesoporous carbon thin films at various temperatures in vapor infiltration method

Mesoporous carbon thin films with ordered structures were prepared by using resorcinol-surfactant self-assembly. A mixture of resorcinol, surfactant, and ethanol coated on silicon substrates was exposed to formaldehyde vapor as a cross-linking agent to form structured resorcinol/formaldehyde resin films. The films were then carbonized at 800 °C in an inert atmosphere to remove the surfactant and to obtain structured carbon materials. With this vapor infiltration method, thin films with several structures were obtained from the same precursor solution by employing different vapor infiltration temperatures. The results were interpreted from the transformation of the self-assembly during the vapor infiltration process.     

交联壳聚糖/蒙脱土复合膜的制备及性能研究

以壳聚糖（CS）为基质材料，蒙脱土（MMT）为填料，采用戊二醛（GA）交联改性并结合溶液插层法制备了交联壳聚糖/蒙脱土（CS/GA/MMT）复合膜。通过扫描电子显微镜、X射线衍射仪、红外光谱仪及热重分析仪对复合膜的结构进行了表征，考察了MMT用量对复合膜的吸水性能、水蒸气阻隔性能和力学性能的影响。结果表明，交联改性CS可提高CS膜的耐水性，CS/GA膜的吸水率较CS膜降低了9.6 %；MMT可提高复合膜的耐水性、水蒸气阻隔性能、力学性能和热稳定性；当MMT的用量为CS质量的5 %时，复合膜的各项性能较好，吸水率、水蒸气透过率和断裂伸长率较CS膜分别降低了37.3 %、36.7 %和41.9 %，且拉伸强度提高了160.5 %。     

Effects of plasticizer/cross-linker on the mechanical and thermal properties of starch/PVA blends

Biodegradable blends of potato starch and polyvinyl alcohol were prepared by solution casting method. Citric acid was employed to introduce the plasticizing effect into the starch materials. Glutaraldehyde as cross-linker was used to enhance the properties of the blend films. Cross-linking is a common method to improve the strength and stability of starch products. The effects of citric acid and glutaraldehyde on the mechanical properties, thermal properties and swelling degree were investigated. The prepared films were measured for their antibacterial activities and biodegradability. The blend samples were characterized by the thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and FTIR analysis techniques. From the mechanical properties study, it was analyzed that the blend films showed improvement in their tensile strength after cross-linking with glutaraldehyde. The SEM micrographs indicated that the blend films were smooth without any cracks, pores and were well cross-linked. The TGA curves showed that there was an increase in the thermal stability of the blend films after cross-linking as compared to uncross-linked blend films. The prepared films showed good antibacterial properties against Gam-positive and Gram-negative bacteria. The biodegradability of the blends was determined by placing the samples in compost soil for different time intervals and were found to be biodegradable in nature.     

Preparation and evaluation of an antibacterial dental cement containing quaternary ammonium salts

A novel PQAS‐containing antibacterial glass‐ionomer cement has been developed. The functional QAS and their constructed PQAS were synthesized, characterized, and formulated into the light‐cured cements. Compressive strength (CS) and bacterial (S. mutans and lactobacillus) viability were used to evaluate the mechanical strength and antibacterial activity of the cements. Flexural (FS) and diametral tensile strengths (DTS) were tested as well. Fuji II LC cement was used as control. The specimens were conditioned in distilled water at 37°C for 24 h prior to testing. All the PQAS‐containing cements showed a significant antibacterial activity, accompanying with an initial CS reduction. The effects of chain length, loading, and grafting ratio of the QAS were significant. Increasing chain length, loading, grafting ratio significantly enhanced antibacterial activity but reduced the initial CS of the formed cements. The antibacterial effect of the substitute chain lengths from free QAS seem more significant in water than those from their polymers (PQAS) after integrating to the cement. The experimental cement showed less CS reduction and higher antibacterial activity than Fuji II LC. The long‐term aging study indicates that the cement might have a long‐lasting antibacterial function with no PQAS leaching. Within the limitations of this study, it appears that the experimental cement is a clinically attractive dental restorative that can be potentially used for long‐lasting restorations due to its high mechanical strength and long‐lasting antibacterial function. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

L1_0有序FePt磁记录薄膜研究进展

L10有序FePt合金薄膜具有高磁晶各向异性能、高矫顽力、高磁能积、高居里温度和抗腐蚀能力强等优点,能够满足超高密度磁记录的要求,极有可能成为下一代超高密度磁存储介质。详细介绍了FePt薄膜近年来的研究成果,分析了降低FePt有序化温度,减小FePt颗粒的粒径,减弱晶粒间相互作用和控制其易磁化轴取向的方法,并对其应用前景作了分析。