An increased sustainabile awarness has inspired the development of new polymeric networks in a remarkable way and this strive should be combined with environmentally concerned end‐uses. Therefore, a UV‐crosslinked polyhydroxyurethane film with antibacterial properties is developed. First, a hydroxyurethane precursor is synthesized using aminolysis condensation, circumventing the use of isocyanates. The films are subsequently crosslinked under solvent‐free conditions through a UV‐triggered thiol‐ene mechanism. The reactions are monitored by 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy, and the networks have gel contents above 90%, and are transparent, hydrophilic, and highly flexible. Antibacterial properties are achieved by a controlled quaternization of the network's tertiary‐amine and methylation of thiol‐ether functionality, resulting in quaternary ammonium compounds (QACs) and sulfonium compounds. The antibacterial properties are evaluated against both Escherichia coli and Staphylococcus aureus using the agar plate diffusion and tube shaking methods. The QAC‐loaded films exhibit outstanding bactericide properties (>99.9%) and the antibacterial mechanism is demonstrated to be a dual killing mechanism, i.e., diffusion killing and contact active killing. 相似文献
We report a simple and effective strategy for fabrication of the nanocomposite containing chitosan (CS) and multiwall carbon nanotube (MWNT) coated on a glassy carbon electrode (GCE). The characterization of the modified electrode (CS‐MWNT/GC) was carried out using scanning electron microscopy (SEM) and UV–vis absorption spectroscopy. The electrochemical behavior of CS‐MWNT/GC electrode was investigated and compared with the electrochemical behavior of chitosan modified GC (CS/GC), multiwalled carbon nanotube modified GC (MWNT/GC) and unmodified GC using cyclic voltammetry (CV) and electron impedance spectroscopy (EIS). The chitosan films are electrochemically inactive; similar background charging currents are observed at bare GC. The chitosan films are permeable to anionic Fe(CN)63?/4? (FC) redox couple. Electrochemical parameters, including apparent diffusion coefficient for the Fe(CN)63?/4? redox probe at FC/CS‐MWNT/GC electrode is comparable to values reported for cast chitosan films. This modified electrode also showed electrocatalytic effect for the simultaneous determination of D‐penicillamine (D‐PA) and tryptophan (Trp). The detection limit of 0.9 μM and 4.0 μM for D‐PA and Trp, respectively, makes this nanocomposite very suitable for determination of them with good sensitivity. 相似文献
The diffusion of Pb through Pb(Zr0.2Ti0.8)O3(PZT)/Pt/Ti/SiO2/Si thin film heterostructures is studied by using time‐of‐flight secondary ion mass spectrometry depth profiling. The as‐deposited films initially contained 10 mol% Pb excess and were thermally processed at temperatures ranging from 325 to 700°C to promote Pb diffusion. The time‐of‐flight secondary ion mass spectrometry depth profiles show that increasing processing temperature promoted Pb diffusion from the PZT top film into the buried heterostructure layers. After processing at low temperatures (eg, 325°C), Pb+ counts were low in the Pt region. After processing at elevated temperatures (eg, 700°C), significant Pb+ counts were seen throughout the Pt layer and into the Ti and SiO2 layers. Intermediate processing temperatures (400, 475, and 500°C) resulted in Pb+ profiles consistent with this overall trend. Films processed at 400°C show a sharp peak in PtPb+ intensity at the PZT/Pt interface, consistent with prior reports of a Pt3Pb phase at this interface after processing at similar temperatures. 相似文献
Transparent and flexible gas‐barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh‐gas‐barrier films with a brick–mortar–sand structure fabricated by layer‐by‐layer (LBL) assembly of XAl‐layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO2 infilling, denoted as (XAl‐LDH/PAA)n‐CO2. The near‐perfectly parallel orientation of the LDH “brick” creates a long diffusion length to hinder the transmission of gas molecules in the PAA “mortar”. Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO2 acts like “sand” to fill the free volume at the organic–inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl‐LDH/PAA)n‐CO2 film is among the best gas barrier films ever reported. 相似文献
Dye‐sensitized solar cells (DSCs) with nanotubular TiO2 electrodes of varying thicknesses are compared to DSCs based on conventional nanoparticulate electrodes. Despite the higher degree of order in one‐dimensional nanotubular electrodes, electron transport times and diffusion coefficients, determined under short‐circuit conditions, are comparable to those of nanoparticulate electrodes. The quasi‐Fermi level, however, is much lower in the nanotubes, suggesting a lower concentration of conduction band electrons. This provides evidence for a much higher diffusion coefficient for conduction band electrons in nanotubes than in nanoparticulate films. The electron lifetime and the diffusion length are significantly longer in nanotubular TiO2 electrodes than in nanoparticulate films. Nanotubular electrodes have a trap distribution that differs significantly from nanoparticulate electrodes; they possess relatively deeper traps and have a characteristic energy of the exponential distribution that is more than two times that of nanoparticulate electrodes.相似文献
A comprehensive dynamic diffusion model is developed to calculate the diffusion coefficients of low molecular weight penetrants (i.e., α‐olefins) in semi‐crystalline polyolefins from dynamic sorption measurements. The model also takes into account the extent of polymer swelling on the penetrant diffusion flux, resulting in a moving boundary value problem. The free volume theory is employed to calculate the dependence of the diffusion coefficient on the penetrant concentration. The solubilities and diffusivities of ethylene and propylene in semi‐crystalline high density polyethylene films were measured at different temperatures and pressures, using a Rubotherm® magnetic suspension microbalance operated in series with an optical view cell for the measurement of the degree of polymer swelling. It is shown that model predictions are in excellent agreement with the experimental dynamic measurements on the mass uptake of the sorbed species. Moreover, it is shown that the proposed model can predict correctly the diffusion coefficient of α‐olefins in semi‐crystalline polyolefins.
Transparent and flexible gas‐barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh‐gas‐barrier films with a brick–mortar–sand structure fabricated by layer‐by‐layer (LBL) assembly of XAl‐layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO2 infilling, denoted as (XAl‐LDH/PAA)n‐CO2. The near‐perfectly parallel orientation of the LDH “brick” creates a long diffusion length to hinder the transmission of gas molecules in the PAA “mortar”. Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO2 acts like “sand” to fill the free volume at the organic–inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl‐LDH/PAA)n‐CO2 film is among the best gas barrier films ever reported. 相似文献
Diffusion of antibody protein from hydrogel films and hydrogel encapsulated in a microcapillary was studied. Thin hydrogel
films were formed by crosslinking 6-acryloyl-B-O-methylgalactoside withN,N’-methylene-bis-acrylamide and the diffusive transport of monoclonal antimouse IgG-FITC into and out of the hydrated films was measured.
Diffusion coefficients in 2 and 4% crosslinked hydrogel films were measured. The measured diffusion constants determined for
IgG in both the 2 and 4% hydrogel films were comparable to the free diffusion of IgG in bulk water (Dmean ∼ 10-7cm2/s). In addition, 2% crosslinked hydrogels were prepared in a capillary tube and the transport of antimouse IgG-FITC into
and out of the hydrated hydrogel was measured. Kinetic analysis indicated that the protein transport through the capillary
hydrogel was faster than would be expected for a simple diffusion process. Finally, by utilizing the diffusion of antibody
from the capillary hydrogel, transfer of antibody to a silica surface was demonstrated. A capillary hydrogel loaded with antimouse
IgG-FITC was used to transfer the protein to a silica surface forming a 30-μm spot of antibody, which was imaged using fluorescence
microscopy. These results may lead to the development of a nonlithographic method of patterning antibodies on surfaces for
use in integrated microimmunosensors. 相似文献
Bacterial polyhydroxyalkanoates (PHAs) are perceived to be a suitable alternative to petrochemical plastics because they have
similar material properties, are environmentally degradable, and are produced from renewable resources. In this study, the
in situ degradation of medium-chain-length PHA (PHAMCL) films in tropical forest and mangrove soils was assessed. The PHAMCL was produced by Pseudomonas putida PGA1 using saponified palm kernel oil (SPKO) as the carbon source. After 112 d of burial, there was 16.7% reduction in gross
weight of the films buried in acidic forest soil (FS), 3.0% in the ones buried in alkaline forest soil by the side of a stream
(FSst) and 4.5% in those buried in mangrove soil (MS). There was a slight decrease in molecular weight for the films buried
in FS but not for the films buried in FSst and in MS. However, no changes were observed for the melting temperature, glass
transition temperature, monomer compositions, structure, and functional group analyses of the films from any of the burial
sites during the test period. This means that the integral properties of the films were maintained during that period and
degradation was by surface erosion. Scanning electron microscopy of the films from the three sites revealed holes on the film
surfaces which could be attributed to attack by microorganisms and bigger organisms such as detritivores. For comparison purposes,
films of polyhydroxybutyrate (PHB), a short-chain-length PHA, and polyethylene (PE) were buried together with the PHAMCL films in all three sites. The PHB films disintegrated completely in MS and lost 73.5% of their initial weight in FSst, but
only 4.6% in FS suggesting that water movement played a major role in breaking up the brittle PHB films. The PE films did
not register any weight loss in any of the test sites. 相似文献
Mesoporous films of platinized carbon nanotube–zirconia–Nafion composite have been used for the immobilization of tris(2,2′‐bipyridyl)ruthenium (II) (Ru(bpy)32+) on an electrode surface to yield a solid‐state electrogenerated chemiluminescence (ECL) sensor. The composite films of Pt–CNT–zirconia–Nafion exhibit much larger pore diameter (3.55 nm) than that of Nafion (2.82 nm) and thus leading to much larger ECL response for tripropylamine (TPA) because of the fast diffusion of the analyte within the films. Due to the conducting and electrocatalytic features of CNTs and Pt nanoparticles, their incorporation into the zirconia–Nafion composite films resulted in the decreased electron transfer resistance within the films. The present ECL sensor based on the Pt–CNT–zirconia–Nafion gave a linear response (R2=0.999) for TPA concentration from 3.0 nM to 1.0 mM with a remarkable detection limit (S/N=3) of 1.0 nM, which is much lower compared to those obtained with the ECL sensors based on other types of sol‐gel ceramic–Nafion composite films such as silica–Nafion and titania–Nafion. 相似文献
Gallic acid (GA)–loaded cellulose acetate (CA) nanofiber mats with 10 to 40 wt.% GA contents (based on the weight of CA) were fabricated by electrospinning. The effects of GA contents and applied potential on the morphology and the average diameters of fibers were studied. The electrospun fiber mats containing 20 and 40 wt.% GA were investigated for their potential use as carrier of GA in wound dressing application. The GA‐loaded CA films were prepared by solvent casting technique for use in comparative studies. Determination of the release characteristics of GA from the GA‐loaded fiber mats and films was carried out by the total immersion and the transdermal diffusion through a pig skin method in acetate buffer solution (pH 5.5) or normal saline (pH 7.0) at either 32 or 37°C, respectively. In the total immersion method, the maximum amounts of the GA released from the fiber mats containing 20 and 40 wt.% GA in the acetate buffer were approximately 97% and 71% (based on the weight of initial GA), while those of the GA released into the normal saline were approximately 96% and 81%, respectively. Lower values were observed in the experiments of the transdermal diffusion through a pig skin method. The corresponding GA‐loaded CA films showed the lower amounts of GA released into media. The as‐loaded and the as‐released GA remained its antioxidant activity as investigated by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) assay. Lastly, the GA‐loaded CA fiber mats exhibited antibacterial activity against Staphylococcus aureus, which showed the potential for use as wound dressing materials. 相似文献