Dynamic mechanical properties of high molecular weight nylon 66 fiber

Dynamic mechanical properties of the ultrahigh molecular weight nylon 66 film and fiber produced by thermally induced solid-state polycondensation are presented. The α peak temperature of tan δ of these treated films and fibers is shifted 8–32°C higher than that of the appropriate control nylon 66 (film and fiber) while the maximum height of the tan δ peaks is decreased. The treated fibers have higher moduli at all temperatures (20–145°C) and humidities (30% RH) than do their control counterparts. The moduli of the treated fibers at 30% RH compare favorably with control yarn at 0% RH. These yarns also have a greater per cent of the 25°C modulus retention as temperature increases.     

How room-humidity during the coating affects the structural,optical and photocatalytic properties of TiO<Subscript>2</Subscript> films

TiO₂ thin films were obtained on glass slide substrates by the sol–gel technique. The substrates were coated by the immersion-removal method, at a constant withdrawal speed. The TiO₂ precursor solution and the substrate were maintained in a closed box with a controlled relative humidity (RH) during the removal of the substrate. The RH was varied in the 30–90% range in steps of 20%. The films were dried and after that sintered in an open atmosphere. The effect of the RH was studied on the structural, optical and photocatalytic properties. The films are polycrystalline with an anatase phase and show a high optical transmission in the UV–Vis range. The photocatalytic activity was evaluated by the photobleaching of methylene blue in an aqueous solution. The best photocatalytic activity was obtained for the films with 90% RH, this fact is mainly attributed to the highest porosity value obtained for these films.     

Investigation of relative humidity effects on the response behavior of a pH indicator-based OWG vapor sensor

The response of a pH indicator-based optical waveguide sensor was characterized with respect to the effects of relative humidity (RH) on the magnitude of the sensor response, and on the rate of response to both hydrochloric acid and ammonia/ammonium hydroxide vapors. Water vapor constitutes both a chemical and a systematic (optical) interference for the OWG sensor response to hydrochloric acid. Swelling of the polymer films upon exposure to water vapor results in a decrease in the loss of light at the polymer/air interface, resulting in an increase in the sensor signal. In addition, high RH conditions decrease the bromothymol blue indicator response to hydrochloric acid vapor. In contrast, the bromothymol blue indicator response to ammonia increases as the RH increases. High RH levels also increases the rate of diffusion (transport) of hydrochloric acid into (and out of) Nafion films, but does not affect the diffusion rate for poly(vinyl alcohol) polymer films. The RH does not appear to have any significant effect on the rate of transport of ammonia in any of the polymer films studied.     

Thin films composed of multiwalled carbon nanotubes, gold nanoparticles and myoglobin for humidity detection at room temperature.

Optically transparent and electrically conductive nanocomposite thin films consisting of multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs) and myoglobin molecules that glue GNPs and MWCNTs together are fabricated for the first time on glass substrates from aqueous solution. The nanocomposite thin film is capable of varying its resistance, impedance or optical transmittance at room temperature in response to changes in ambient humidity. The conductometric sensitivity to relative humidity (RH) of the nanocomposite thin film is compared with those of the pure and Mb-functionalized MWCNT layers. The pure MWCNT layer shows a small increase in its resistance with increasing RH due to the effect of p-type semiconducting nanotubes present in the film. In contrast, a four times higher sensitivity to RH is observed for both the nanocomposite and Mb-functionalized MWCNT thin films. The sensitivity enhancement is attributable to swelling of the thin films induced by water absorption in the presence of Mb molecules, which increases the inter-nanotube spacing and thereby causes a further increase of the film resistance. A humidity change as low as DeltaRH=0.3 % has been readily detected by conductometry using the nanocomposite thin film.     

Layer-by-layer immobilization of carbon dots fluorescent nanomaterials on single optical fiber

We report within this paper the development of a fiber-optic based sensor for Hg(II) ions. Fluorescent carbon nanoparticles were synthesized by laser ablation and functionalized with PEG₂₀₀ and N-acetyl-l-cysteine so they can be anionic in nature. This characteristic facilitated their deposition by the layer-by-layer assembly method into thin alternating films along with a cationic polyelectrolyte, poly(ethyleneimine). Such films could be immobilized onto the tip of a glass optical fiber, allowing the construction of an optical fluorescence sensor. When immobilized on the fiber-optic tip, the resultant sensor was capable of selectively detecting sub-micromolar concentrations of Hg(II) with an increased sensitivity compared to carbon dot solutions. The fluorescence of the carbon dots was quenched by up to 44% by Hg(II) ions and interference from other metal ions was minimal.     

金微盘电极的加工和表征

微电极具有常规电极无法比拟的优良的电化学特性^[1,2].它包括单微电极和微电极阵列, 其中单微电极的整体尺寸小, 可用于微区分析研究. 目前微盘电极的工艺改善目标主要包括: 电极整体尺寸小、 电极材料和绝缘层之间的粘附性高及电极具有明确的和可重复的形状和尺寸等^[3]方面.     

Highly sensitive optical humidity probe

A highly sensitive optical humidity probe based on reflectance measurements has been developed using Nafion^®-crystal violet (CV) films. This sensor can be used to calibrate relative humidity (RH) in the range 0-0.25% with a detection limit (blank signal + 3σ_b, where σ_b = the standard deviation (S.D.) of the blank signal) of 0.018% RH (∼4.37 ppm) and exhibited low hysteresis. The sensor films were fully reversible in dry nitrogen and reversal times were shown to be dependent on exposure time and % RH. The response to 1% RH was highly reproducible (S.D. = 1.67%, number of samples (n) = 5). Hydrogen chloride gas did not interfere with the response of the sensor to RH but did reduce sensor reversal times. This sensor displayed sufficient sensitivity that it could be used to detect ppm levels of moisture in process gases such as nitrogen and HCl.     

Simplification and evaluation of a gold-deposited SPR optical fiber sensor.

The structure of the sensing element of a gold-deposited optical fiber sensor was simplified and quantitative analyses of various alcohols with the sensor showed improvement of the performance. The sensor uses surface plasmon resonance (SPR) at the interface of a sample solution and a thin (10 - 70 nm) gold film deposited on half of the exposed core of the optical fiber. The sensor with a film thickness of 45 nm can detect a small change of 5.6 x 10(-5) refractive index (RI) units in the refractivity. The response time is less than 0.5 min and the relative standard deviation for measurements is less than or equal to 1%. A straight line with a correlation coefficient of 0.9995 was obtained below 10%, v/v in the calibration curve for methanol solutions of benzyl alcohol. The minimum of the response curve due to the maximum excitation of SPR in the refractivity range from 1.33 to 1.44 RI units shifts to a lower refractivity as the film becomes thicker. The response curves of the sensors were calculated from SPR theoretical equations while considering of the distribution in the thickness of the deposited gold films. The improvement in the performance of the sensor is discussed.     

Theoretical analysis of gold-deposited optical fiber sensor and characterization of the gold film.

Gold-deposited optical fiber sensors with film thicknesses from 30 to 60 nm were prepared, and the responses to a wide range of a refractivity (1.33-1.54 refractive index (RI) units) were investigated both experimentally and theoretically. The response curve of the sensor has two minima in the refractivity range from 1.33 to 1.44 and at 1.462 RI units. The former minimum is due to surface plasmon resonance (SPR) in the thin gold film, and shifts to a lower refractivity as the film becomes thicker. The response curves of the sensors with film thicknesses of 45 and 60 nm agreed well with those calculated from SPR theoretical equations. Morphology observations of the surfaces of deposited gold films on glass by atomic force microscopy (AFM) and a variation in resistance of the films with various thicknesses show the structure of the gold films. We concluded that the thin deposited gold films have many defects, and that the core of the gold-deposited optical fiber leaks light through the defects to the sample solution with the same refractivity (1.462 RI units) as that of the core.     

Starch-iodine films respond to water vapor

Starch-iodine indicator films were found to have useful spectroscopic properties for the detection of water vapor. The large colorimetric response of these easily prepared films was easily detected by the absorption of 632.8 nm HeNe laser light, using a planar integrated optical waveguide (IOW) platform. The detection limit of a prototype sensor was found to be below 5% relative humidity (RH), with response times of the order of seconds.     

Fluorescent Optosensor for Humidity Measurements in Air

A fiber‐optic sensor for relative‐humidity (RH) monitoring in environmental samples is described based on the adiabatic photoreaction that produces an intramolecular charge‐transfer excited state, which is the basis of the sensor response. The sensitive membranes are obtained immobilizing a highly fluorescent dye, 4‐[2‐(pyrazin‐2‐yl)‐1,3‐oxazol‐5‐yl]benzenamine (pzoxba; formerly called appzox), in hydroxypropylcellulose (HPC). The composition of the sensing films was optimized to a final ratio pzoxba/HPC of 1.8⋅10⁻⁵ mol g⁻¹ with a 100‐μm membrane thickness. The optode response spans from 1.68 to 100% RH, with a detection limit of 0.56% (Table 2). Typical response times (t₉₀) to 0 – 100% relative humidity are 1 – 2 min, the relative standard deviation for repeated measurements being 0.77 – 1.8%. The optode is insensitive to typical organic vapor interferents of commercial capacitive sensors (see Table 3) as well as to molecular oxygen, an important quencher of other luminescence‐based optical sensors. The proposed optode was successfully applied and validated for continuous monitoring of the relative humidity level in environmental samples.     

氧化锌薄膜/锡掺杂玻璃光波导元件及其对氯苯的气敏性研究

建立了玻璃光波导气敏元件检测氯苯气体的方法.采用浸渍-提拉法将ZnO敏感膜固定在锡掺杂玻璃光波导表面,研制出了检测氯苯气体的ZnO薄膜/锡掺杂玻璃光波导气敏元件,并用该玻璃光波导气敏元件对挥发性有机气体进行了检测.实验结果表明,在室温下,气敏元件对氯苯气体有明显的响应,而对相同浓度的其它挥发性有机气体的响应相对较小,对...     

Comparison of formats for the development of fiber-optic biosensors utilizing sol-gel derived materials entrapping fluorescently-labelled protein

The development of fiber-optic biosensors requires that a biorecognition element and a fluorescent reporter group be immobilized at or near the surface of an optical element such as a planar waveguide or optical fiber. In this study, we examined a model biorecognition element-reporter group couple consisting of human serum albumin that was site-selectively labelled at Cys 34 with iodoacetoxy-nitrobenzoxadiazole (HSA-NBD). The labelled protein was encapsulated into sol-gel derived materials that were prepared either as monoliths, as beads that were formed at the distal tip of a fused silica optical fiber, or as thin films that were dipcast along the length of a glass slide or optical fiber. For fiber-based studies, the entrapped protein was excited using a helium-cadmium laser that was launched into a single optical fiber, and emission was separated from the incident radiation using a perforated mirror beam-splitter, and detected using a monochromator-photomultiplier tube assembly. Changes in fluorescence intensity were generated by denaturant-induced conformational changes in the protein or by iodide quenching. The analytical parameters of merit for the different encapsulation formats, including minimum protein loading level, response time and limit-of-detection, were examined, as were factors such as protein accessibility, leaching and photobleaching. Overall, the results indicated that both beads and films were suitable for biosensor development. In both formats, a substantial fraction of the entrapped protein remained accessible, and the entrapped protein retained a large degree of conformational flexibility. Thin films showed the most rapid response times, and provided good detection limits for a model analyte. However, the entrapment of proteins into beads at the distal tip of fibers provided better signal-to-noise and signal-to-background ratios, and required less protein for preparation. Hence, beads appear to be the most viable method for interfacing of proteins to optical fibers.     

pH值与湿度的光纤传感器研究

本文采用溶胶凝胶法和包埋法分别将对pH值和湿度敏感的指示剂修饰在光纤纤芯表面,制成了具有较宽检测范围的光纤pH传感器和光纤湿度传感器。通过X射线能谱仪(EDX)对所制备的pH和湿度敏感膜的表面成分进行了分析,并采用光功率计对敏感膜进行了光学检测。结果表明:当pH值在4.5~13的范围内变化时,光输出功率与pH值近似呈线性变化规律;当相对湿度(RH)在25%~80%的范围内变化时,光输出功率与RH值近似呈线性变化规律,并且二者在其检测范围内均具有良好的可逆性。     

Polyelectrolytes in thin liquid films

The review addresses the influence of polyelectrolytes on the statics and dynamics of thin liquid films. Both, changes of interfacial and bulk properties, contribute to the overall behaviour of thin films formed from aqueous polyelectrolyte solutions. Therefore, the chapter is separated into two parts: polyelectrolytes at film interfaces and polymers in film bulk.     

Nanocomposite-based lignocellulosic fibers 1. Thermal stability of modified fibers with clay-polyelectrolyte multilayers

The layer-by-layer (LbL) assembly process of creating highly structured thin films derived from layers of polyelectrolytes and nanoparticles was adopted in this study to modify the surface of lignocellulosic fibers. Aqueous dispersions of clay nanoplatelets were created with ultrasonication and characterized with dynamic light scattering and atomic force microscopy in which confirmed the presence of individual clay nanoplatelets. Film thickness of never-dried clay and poly(diallyldimethylammonium chloride) (PDDA) multilayers was studied with a quartz crystal microbalance with dissipation monitoring (QCM-D). Using identical LbL deposition parameters, a slurry of steam-exploded wood fibers was modified by alternate adsorption of PDDA and clay with multiple rinsing steps after each adsorption cycle. Zeta potential measurements were used to characterize the fiber surface charges after each adsorption step while SEM images revealed that the LbL film masked the cellulose microfibril structure. Using a thermogravimetric analyzer, LbL modified steam-exploded wood fibers were observed to attain increased thermal stability relative to the unmodified material tested in both air and nitrogen atmospheres. Significant char for the LbL clay coated steam-exploded wood suggests the multilayer film serves as a barrier creating an insulating layer to prevent further decomposition of the material. This nanotechnology may have a positive impact on the processing of lignocellulosic fibers in thermoplastic matrices, designing of paper-based overlays for building products, and modification of cellulosic fibers for textiles.     

Glucose oxidase-incorporated hydrogel thin film for fast optical glucose detecting under physiological conditions

Hydrogel biosensors usually suffer from a slow response, which severely hinders their practical applications. Here a new optical glucose biosensor was designed, using glucose-sensitive hydrogel films as both glucose-sensing material and Fabry-Perot cavity. The film was fabricated by layer-by-layer assembly from partially oxidized dextran (PO-Dex), chitosan, and glucose oxidase (GOD). The film responds to glucose because the incorporated GOD converts glucose to gluconic acid, and thus lowers the local pH in the film, and, in turn, triggers the pH-sensitive film to swell. The glucose-induced swelling causes a shift of Fabry?Perot fringes on the reflection spectra of the film, from which the glucose concentration can be reported. The new sensor works well under physiological conditions. Potential interferents, such as diols for phenylboronic acid-based sensors and electroactive compounds for electrochemical sensors, do not influence the new sensor. The sensor can respond reversibly over a wide range of glucose concentration. Particularly, it responds linearly within the clinically relevant glucose range (0–20 mM). More importantly, because the film is very thin, the new sensor can respond quickly, making it potential for real-time, continuous glucose monitoring.     

Photochemical modification of an optical fiber tip with a silver nanoparticle film: a SERS chemical sensor

We present a method of photochemical modification of an optical fiber tip with a silver nanoparticle film. The deposited silver nanoparticle film displays alternating light and dark circles, which are similar to a radial diffraction pattern. The modified optical fiber is examined as a chemical sensor for in situ detection. The modified fibers show excellent SERS activity, a low limit of detection (LOD), and good reproducibility. The maximum SERS activity of the sensor was achieved within 5.0 min of deposition. Thus, the method is also quite rapid.     

温度敏感水凝胶包覆长周期光纤光栅传感器研究

以N-异丙基丙烯酰胺(NIPAM)为单体、N,N'-亚甲基双丙烯酰胺(MBAA)为交联剂、安息香二甲醚(DMPA)为引发剂,利用紫外光引发聚合制备了一系列温度敏感性聚(N-异丙基丙烯酰胺)(PNIPAM)水凝胶,并对其性能进行了测定.结果表明,PNIPAM水凝胶的平衡膨胀比随着交联程度的变化而改变.当交联程度适当时,水凝胶可具有最大的溶胀比.在此研究基础上,利用浸渍提拉法在长周期光纤光栅(LPFG)包层外制备了PNIPAM水凝胶薄膜包覆层.研究了得到的LPFG传感器对温度和湿度的响应性,该类型传感器表现出对温度的灵敏响应性.     

Electrical and humidity characterization of m-NA doped Au/PVA nanocomposites

The Meta-Nitroaniline (m-NA) doped (by varying weight percentage (wt. %)) gold/polyvinyl alcohol (Au/PVA) nanocomposites were synthesized using gold salt and hydrazine hydrate (HH) by in situ process. The composite was coated on ceramic rods having two end electrodes by drop casting method for studying their electrical behavior at different relative humidity (RH) levels, ranging from 4 to 95% RH at room temperature. The optimized wt. % was used to prepare coatings of various thicknesses (20-40 μm) of the films. As the humidity decreases, the resistance increases. The low humidity sensing characteristic can be tailored by varying wt. % of m-NA and thicknesses of the nanocomposite films. The resistive-humidity sensor shows two regions of sensitivity having highest sensitivity for lower RH. The sensor response and recovery time is about 6-10 s and 52 s respectively. The dynamic range of variation of the resistance allows a promising use of the films as a humidity sensor. The material was characterized by X-ray diffraction (XRD) and impedance spectroscopy at 60% RH.