Use of silver and silver salts is as old as human civilization but the fabrication of silver nanoparticles (Ag NPs) has only recently been recognized. They have been specifically used in agriculture and medicine as antibacterial, antifungal and antioxidants. It has been demonstrated that Ag NPs arrest the growth and multiplication of many bacteria such as Bacillus cereus, Staphylococcus aureus, Citrobacter koseri, Salmonella typhii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Vibrio parahaemolyticus and fungus Candida albicans by binding Ag/Ag+ with the biomolecules present in the microbial cells. It has been suggested that Ag NPs produce reactive oxygen species and free radicals which cause apoptosis leading to cell death preventing their replication. Since Ag NPs are smaller than the microorganisms, they diffuse into cell and rupture the cell wall which has been shown from SEM and TEM images of the suspension containing nanoparticles and pathogens. It has also been shown that smaller nanoparticles are more toxic than the bigger ones. Ag NPs are also used in packaging to prevent damage of food products by pathogens. The toxicity of Ag NPs is dependent on the size, concentration, pH of the medium and exposure time to pathogens.

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A review on biosynthesis of silver nanoparticles and their biocidal properties.

The solution of electromagnetic scattering by a homogeneous prolate (or oblate) spheroidal particle with an arbitrary size and refractive index is obtained for any angle of incidence by solving Maxwell's equations under given boundary conditions. The method used is that of separating the vector wave equations in the spheroidal coordinates and expanding them in terms of the spheroidal wavefunctions. The unknown coefficients for the expansion are determined by a system of equations derived from the boundary conditions regarding the continuity of tangential components of the electric and magnetic vectors across the surface of the spheroid. The solutions both in the prolate and oblate spheroidal coordinate systems result in a same form, and the equations for the oblate spheroidal system can be obtained from those for the prolate one by replacing the prolate spheroidal wavefunctions with the oblate ones and vice versa. For an oblique incidence, the polarized incident wave is resolved into two components, the TM mode for which the magnetic vector vibrates perpendicularly to the incident plane and the TE mode for which the electric vector vibrates perpendicularly to this plane. For the incidence along the rotation axis the resultant equations are given in the form similar to the one for a sphere given by the Mie theory. The physical parameters involved are the following five quantities: the size parameter defined by the product of the semifocal distance of the spheroid and the propagation constant of the incident wave, the eccentricity, the refractive index of the spheroid relative to the surrounding medium, the incident angle between the direction of the incident wave and the rotation axis, and the angles that specify the direction of the scattered wave.

Light Scattering by a Spheroidal Particle

Antimony selenide (Sb2Se3) has a one-dimensional (1D) crystal structure comprising of covalently bonded (Sb4Se6)n ribbons stacking together through van der Waals force. This special structure results in anisotropic optical and electrical properties. Currently, the photovoltaic device performance is dominated by the grain orientation in the Sb2Se3 thin film absorbers. Effective approaches to enhance the carrier collection and overall power-conversion efficiency are urgently required. Here, we report the construction of Sb2Se3 solar cells with high-quality Sb2Se3 nanorod arrays absorber along the [001] direction, which is beneficial for sun-light absorption and charge carrier extraction. An efficiency of 9.2%, which is the highest value reported so far for this type of solar cells, is achieved by junction interface engineering. Our cell design provides an approach to further improve the efficiency of Sb2Se3-based solar cells.

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9.2%-efficient core-shell structured antimony selenide nanorod array solar cells

Ferrite nanoparticles (FNPs) have attracted a great interest due to their wide applications in several areas such as biomedical, wastewater treatment, catalyst and electronic device. This review focuses on the synthesis, characterisation and application of FNPs in electronic device with more emphasis on the recently published works. The most commonly used synthesis techniques along with their advantages and limitations are discussed. The available characterisation techniques and their application in electronic materials such as sensors and biosensors, energy storage, microwave device, electromagnetic interference shielding and high-density recording media are briefly reviewed.

Ferrite nanoparticles: Synthesis, characterisation and applications in electronic device

Antimony selenosulfide, Sb2(S,Se)3, has attracted attention over the last few years as a light-harvesting material for photovoltaic technology owing to its phase stability, earth abundancy and low toxicity. However, the lack of a suitable material processing approach to obtain Sb2(S,Se)3 films with optimal optoelectronic properties and morphology severely hampers prospects for efficiency improvement. Here we demonstrate a hydrothermal approach to deposit high-quality Sb2(S,Se)3 films. By varying the Se/S ratio and the temperature of the post-deposition annealing, we improve the film morphology, increase the grain size and reduce the number of defects. In particular, we find that increasing the Se/S ratio leads to a favourable orientation of the (Sb4S(e)6)n ribbons (S(e) represents S or Se). By optmizing the hydrothermal deposition parameters and subsequent annealing, we report a Sb2(S,Se)3 cell with a certified 10.0% efficiency. This result highlights the potential of Sb2(S,Se)3 as an emerging photovoltaic material. Antimony chalcogenides are emerging photovoltaic materials, yet difficulties in fabricating high-quality films limit device performance. We show that hydrothermal synthesis affords good morphology and reduced defects in antimony selenosulfide films, enabling solar cells with an efficiency of 10%.

Hydrothermal deposition of antimony selenosulfide thin films enables solar cells with 10% efficiency

Antimony selenide is an emerging promising thin film photovoltaic material thanks to its binary composition, suitable bandgap, high absorption coefficient, inert grain boundaries and earth-abundant constituents. However, current devices produced from rapid thermal evaporation strategy suffer from low-quality film and unsatisfactory performance. Herein, we develop a vapor transport deposition technique to fabricate antimony selenide films, a technique that enables continuous and low-cost manufacturing of cadmium telluride solar cells. We improve the crystallinity of antimony selenide films and then successfully produce superstrate cadmium sulfide/antimony selenide solar cells with a certified power conversion efficiency of 7.6%, a net 2% improvement over previous 5.6% record of the same device configuration. We analyze the deep defects in antimony selenide solar cells, and find that the density of the dominant deep defects is reduced by one order of magnitude using vapor transport deposition process.

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Vapor transport deposition of antimony selenide thin film solar cells with 7.6% efficiency.

Sb2S3 Solar Cells

Sb2Se3 is a promising non-toxic, Earth-abundant, stable thin-film solar cell absorber material. However, the low built-in potential caused by the low intrinsic doping density (∼1013 cm−3) and the low carrier collection efficiency due to the low carrier mobility (∼1.5 cm2 V−1 s−1) hinder further efficiency improvement of Sb2Se3 solar cells. Therefore, an effective hole-transport layer (HTL) is necessary to further boost the built-in potential and assist carrier collection. Herein we attempt to improve the efficiency of Sb2Se3 solar cells by using CuSCN as an HTL. CuSCN as an HTL suppresses the back surface recombination, and enhances the built-in potential and carrier collection efficiency. Meanwhile, materials and physical properties characterization reveals that CuSCN provides Cu ions which induce grain boundary inversion, and therefore separate photo-generated carriers more efficiently. Consequently, we obtained a device efficiency of 7.50%.

Rokas Kondrotas

Papers

Vapor transport deposition of antimony selenide thin film solar cells with 7.6% efficiency.

Sb2S3 Solar Cells

7.5% n–i–p Sb2Se3 solar cells with CuSCN as a hole-transport layer

Biosynthesis of silver nanoparticles using lingonberry and cranberry juices and their antimicrobial activity

Efficiency improvement of flexible Sb2Se3 solar cells with non-toxic buffer layer via interface engineering