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Novel sensitive optical biosensor for determination of Grapevine virus A-type (GVA) proteins (GVA-antigens) has been designed. This biosensor was based on thin films of Zinc Oxide (ZnO) deposited by atomic layer deposition (ALD). The ZnO-based films have demonstrated favorable surface-structural properties for the direct immobilization of antibodies against GVA-antigens in order to form a biosensitive layer sensitive to GVA-antigens. The immobilization was confirmed by intensity changes in the main near band emission (NBE) peak of ZnO and by the formation of intense photoluminescence band, discovered in the visible range around 425nm, caused by the immobilized proteins. The GVA-antigen detection was performed by the evaluation of changes and behavior of a corresponding luminescence band. The sensitivity of as-formed label-free biosensor towards the GVA-antigens was determined in the range from 1pg/ml to 10ng/ml; in addition, the selectivity of biosensor was evaluated.

Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

Articles you may be interested inThe surface-plasmon-resonance and band bending effects on the photoluminescence enhancement of Agdecorated ZnO nanorods J. Appl. Phys. 116, 063108 (2014) The recombination dynamics of neutral donor bound excitons (D o X: I 4 , I 6/6a ) and near band edge defect-related emission in solution grown ZnO nanorods are investigated using steady state and time-resolved photoluminescence (PL) measurements. The effects of annealing are also studied. Low temperature steady state PL shows a systematic removal of the I 4 line after annealing at 450 C and the subsequent domination of I 6a in these PL spectra. Additionally, the time decay of the I 4 , I 6/6a, free exciton (FX), and basal plane stacking fault-related (BSF) PL transitions are studied as a function of annealing temperature. For the various annealing temperatures studied, the PL decay is described by a bi-exponential profile with a fast component (contribution from the surface) and slow component (related to bulk recombination). The fast component dominates in the case of as-grown and low temperature annealed samples (anneal temperatures up to 300 C), suggesting the presence of surface adsorbed impurities. For samples annealed above 400 C, the effects of the surface are reduced. The sample annealed at 850 C produced an overall enhancement of the crystal quality. The underlying mechanisms for the observed PL characteristics are discussed based on near surface band bending caused by surface impurities. V C 2014 AIP Publishing LLC.

Growing InGaN quantum dots (QDs) at the apex of hexagonal GaN pyramids is an elegant approach to achieve a deterministic positioning of QDs. Despite similar synthesis procedures by metal organic chemical vapor deposition, the optical properties of the QDs reported in the literature vary drastically. The QDs tend to exhibit either narrow or broad emission lines in the micro-photoluminescence spectra. By coupled microstructural and optical investigations, the QDs giving rise to narrow emission lines were concluded to nucleate in association with a (0001) facet at the apex of the GaN pyramid.