Optical and electrical nano eco-sensors using alternative deposition of charged layer

This review focuses on layer by layer (LBL) assembly-based nano ecological sensor (hereafter, eco-sensor) for pesticide detection, which is one of the most versatile methods. The effects of pesticides on human health and on the environment (air, water, soil, plants, and animals) are of great concern due to their increasing use. We highlight two of the most popular detecting methods, i.e., fluorescence and electrochemical detection of pesticides on an LBL assembly. Fluorescence materials are of great interest among researchers for their sensitivity and reliable detection, and electrochemical processes allow us to investigate synergistic interactions among film components through charge transfer mechanisms in LBL film at the molecular level. Then, we noted some prospective directions for development of different types of sensing systems.     

Optical properties and crystallinity of hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by rf-PECVD

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared in a home-built radio-frequency (rf) plasma enhanced chemical vapour deposition (PECVD) system have been studied. The rf powers were fixed in the range of 5 W-80 W. The optical properties and crystallinity of the films were studied by X-ray diffraction (XRD), Micro-Raman scattering spectroscopy, high resolution transmission electron microscope (HRTEM), and optical transmission and reflection spectroscopy. The XRD and Micro-Raman scattering spectra were used to investigate the evidence of crystallinity in order to determine the crystallite sizes and crystalline volume fraction in the films. The HRTEM image of the film was used to correlate with the crystallinity that was determined from XRD and Micro-Raman scattering spectra. Optical constants such as refractive index, optical energy gap, Tauc slope, Urbach energy and ionic constants were obtained from the optical transmission and reflectance spectra. From the results, it was interesting to found that the optical constants showed a good correlation with the crystallinity within the variation of rf power. Also, the ionic constants of the films showed an indication of the degree of crystallinity in the films. The variation of the optical energy gap with the rf power based on structure disorder and the quantum confinement effect is discussed.     

An α-K3PMo3W9O40 film loaded with silver nanoparticles: Fabrication, characterization and properties

A composite film consisting of the mixed-addenda Keggin-type polyoxometalate α-K₃PMo₃W₉O₄₀ (PMo₃W₉) and silver nanoparticles (AgNPs) was fabricated on quartz, silicon, and ITO by the layer-by-layer self-assembly method. The regular growth of the multilayer film was monitored by UV–vis spectroscopy, and the morphology was measured by atomic force microscopy (AFM). The multilayer film embedded by AgNPs exhibited the photo-luminescence ascribed to electronic transitions from excited states to d levels of the silver nanoparticles. The composite film also showed electrocatalytic activity towards reduction of NO₂⁻, H₂O₂, ClO₃⁻, BrO₃⁻, and IO₃⁻ attributed to tungsten-centered and molybdenum-centered redox processes of PMo₃W₉.     

Bone morphogenetic protein‐2 immobilization on porous PCL‐BCP‐Col composite scaffolds for bone tissue engineering

The objective of this study was to develop novel porous composite scaffolds for bone tissue engineering through surface modification of polycaprolactone–biphasic calcium phosphate‐based composites (PCL–BCP). PCL–BCP composites were first fabricated with salt‐leaching method followed by aminolysis. Layer by layer (LBL) technique was then used to immobilize collagen (Col) and bone morphogenetic protein (BMP‐2) on PCL–BCP scaffolds to develop PCL–BCP–Col–BMP‐2 composite scaffold. The morphology of the composite was examined by scanning electron microscopy (SEM). The efficiency of grafting of Col and BMP‐2 on composite scaffold was measured by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Both XPS and FTIR confirmed that Col and BMP‐2 were successfully immobilized into PCL–BCP composites. MC3TC3‐E1 preosteoblasts cells were cultivated on composites to determine the effect of Col and BMP‐2 immobilization on cell viability and proliferation. PCL–BCP–Col–BMP‐2 showed more cell attachment, cell viability, and proliferation bone factors compared to PCL–BCP‐Col composites. In addition, in vivo bone formation study using rat models showed that PCL–BCP–Col–BMP‐2 composites had better bone formation than PCL–BCP‐Col scaffold in critical size defect with 4 weeks of duration. These results suggest that PCL–BCP–Col–BMP‐2 composites can enhance bone regeneration in critical size defect in a rat model with 4 weeks of duration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45186.     

Surface immobilisation of transition metal substituted Krebs type polyoxometalates, [X2W20M2O70(H2O)6] (X = Bi or Sb, M = Co or Cu), by the layer by layer technique

A series of transition metal (i.e. Cu²⁺ and Co²⁺) substituted Krebs type polyoxometalates (POMs), of the general formula [X₂W₂₀M₂O₇₀(H₂O)₆]ⁿ⁻, X = Sb or Bi, M = Co(II) or Cu(II), have been successfully immobilised onto carbon electrode surfaces through the employment of the layer-by-layer (LBL) technique. This involved the construction of alternating anionic POM, [X₂W₂₀M₂O₇₀(H₂O)₆]ⁿ⁻, layers and the cationic metallodendrimer, Ru(II)-metallodendrimer as the cationic layers, in addition to a [poly(diallyldimethylammonium chloride)] PDDA base layer. Stable multielectron redox couples associated with the W–O framework, for the Krebs type POMs, and the Ru(III/II) for the metallodendrimer, were clearly observed upon layer construction and redox switching within the pH domain of 2–6.5. The constructed multilayer assemblies exhibited pH dependent redox activity and thin layer behaviour up to 100 mV s⁻¹. The porosity and permeability of the individual multilayer assemblies towards an anionic probe were determined by AC impedance and cyclic voltammetry. The surface morphology of each multilayer was also determined by Atomic Force Microscopy (AFM).     

层层自组装制备透明超疏水表面

利用层层自组装技术在玻璃表面上沉积二氧化硅纳米颗粒与聚苯乙烯球,高温烧结去除苯乙烯球后可在玻璃基底上构筑由二氧化硅纳米颗粒组成的阶层纳米粗糙微观结构,然后利用1H,1H,2H,2H-全氟癸基三乙氧基硅烷(FAS)进行表面疏水化处理制备透明超疏水表面,该表面与水的接触角高达166°。实验考察SiO2颗粒粒径对超疏水表面性能的影响并针对超疏水表面进行了扫描电镜、傅立叶变换红外光谱、接触角及热重表征。     

Carbon nanotube networks on different platforms

Carbon nanotube (CNT) networks are an emerging class of material with potential applications that range from biotechnology to sensors. However, the design and fabrication of CNT networks with specific properties necessitates a deep understanding on how a variety of factors affect the performance of these materials. Of particular interest is how the substrate on which the CNT networks are assembled also influences on the applicational aspects of the CNT network. In this review, we overview the variety of substrates reported as CNT networks supports, and the different applications of these networks. Substrates can be varied from rigid to flexible to porous materials. Interestingly, the method of network preparation and the nature of the scaffold have a direct influence on the properties and the potential applications of the final material.     

氧化石墨烯/壳聚糖层层自组装复合膜的制备及其在环保领域中的应用

利用层层自组装技术将氧化石墨烯与壳聚糖进行自组装,制备出一种新型的氧化石墨烯/壳聚糖复合膜,并利用原位合成的方法引入纳米银粒子。采用紫外可见光谱(UV-Vis)、红外光谱(FTIR)、X射线衍射(XRD)和原子吸收等分析方法对复合膜的自组装行为和催化性能进行了研究。实验结果表明,氧化石墨烯与壳聚糖可通过层层自组装技术制备出新型复合膜,这种复合膜可包裹纳米银粒子,膜内纳米银粒子对4-硝基苯酚的催化活性较高,并且可实现循环使用。此外,在稳定性实验中,复合膜不会释放纳米银粒子或银离子,避免了给水体带来二次污染。因此,这种材料在水处理等环保领域中可能具有巨大的潜在实用价值。