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A pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd(2+), Co(2+), Cu(2+), and Hg(2+). The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.

The worldwide increase in the number of people suffering from diabetes has been the driving force for the development of glucose sensors. The recent past has devised various approaches to formulate glucose sensors using various nanostructure materials. This review presents a combined survey of these various approaches, with emphasis on the current progress in the use of electrospun nanofibers and their composites. Outstanding characteristics of electrospun nanofibers, including high surface area, porosity, flexibility, cost effectiveness, and portable nature, make them a good choice for sensor applications. Particularly, their nature of possessing a high surface area makes them the right fit for large immobilization sites, resulting in increased interaction with analytes. Thus, these electrospun nanofiber-based glucose sensors present a number of advantages, including increased life time, which is greatly needed for practical applications. Taking all these facts into consideration, we have highlighted the latest significant developments in the field of glucose sensors across diverse approaches.

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The core–shell form of ZnO–ZnS based heterostructural nanofibers (NF) has received increased attention for use as a photocatalyst owing to its potential for outstanding performance under visible irradiation.

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Here, we describe the visual colorimetric detection of Hg2+ based on a flexible fluorescent electrospun nanofibrous membrane (NFM). It is an efficient approach, in which we have effectively integrated fluorescent gold nanoclusters (AuNC) into electrospun polyvinyl alcohol nanofibers. Interestingly, the resulting composite nanofibers (AuNC*NFM) are shown to retain the fluorescence properties of AuNC and exhibit red fluorescence under UV light, being cogent criteria for the production of a visual colorimetric sensor. Furthermore, capabilities with regard to the stability of the AuNC*NFM have been under observation for a period of six months, with conditions matching those of typical atmosphere, and the resulting outcome has thrown light on their long-term storability and usability. It is clear, from the fact that the nanofibrous membrane preserves the fluorescence ability up to a temperature of 100 °C, that temperature does not have an effect on the sensing performance in real-time application. The water-insoluble AuNC*NFM have been successfully tailored by cross-linking with glutaraldehyde vapor. Further, the contact mode approach has been taken into consideration for the visual fluorescent response to Hg2+, and the observed change of color indicates the utility of the composite nanofibers for onsite detection of Hg2+ with a detection limit of 1 ppb. The selectivity of the AuNC*NFM hybrid system has been analyzed by its response to other common toxic metal interferences (Pb2+, Mn2+, Cu2+, Ni2+, Zn2+, Cd2+) in water. Several unique features of the hybrid system have been determined, including high stability, self-standing ability, naked-eye detection, selectivity, reproducibility and easy handling-setting a new trend in membrane-based sensor systems. © 2014 the Partner Organisations

Electrospun ZnO nanofibers (ZNF) have received increased attention as photocatalysts owing to their potential for incredible performance. However, uncertainty still exists in determining the correlation between grain boundaries (GBs) and photocatalytic activity. Therefore, effective thought has been put into engineering the GBs to convert ZNF into a promising photocatalyst. Herein, the obtained electrospun ZnO structures are composed of nanograins, which are connected to each other in an ordered manner. Indepth studies have revealed that the growth of nanograins severely altered the morphology of ZNF and GB areas at higher annealing temperatures ranging from 500°C to 1000°C. Based on the morphological features and their structural evolution, the obtained structures are named as ZnO nanofibers-1 (ZNF-1, 500°C), ZnO hollow tubes (ZHT, 600°C), ZnO nanofibers-2 (ZNF-2, 700°C), ZnO bamboo structured fibers (ZBF, 800°C), ZnO segmented fibers (ZSF, 900°C) and ZnO nanoparticles (ZNP, 1000°C). A strong correlation between the inherent emission features of ZNF and their peak positions have been detected with the GB. The comparative degradation efficiency of methylene blue (MB) has been studied and the results showed that the ZNF-1 with highly stacked nanograins containing rich grain boundaries demonstrated ∼6 times higher efficiency than other structures. In addition, it has been shown to have a strong effect towards the degradation of Rhodamine B (Rh B) and 4-nitro-phenol (4-NP). A critical parameter for improving the photocatalytic activity is found to be the GB mediated defects, which are proposed to be oxygen/zinc vacancies at nanograin fusion interfaces, while supposedly maintaining its fibrous structure, wherein no relationship has been drawn implying the direct domination of morphology, surface area and defect.CrystEngComm, 2016, 18, 6341-6351 | 6341This journal is † Electronic supplementary information (ESI) available: SEM image of aselectrospun PVA/zinc acetate composite nanofibers, average grain size measurement, XPS spectra of Zn 2p and photocatalytic recycling performance of ZNF-2. See