Photoinduced shape conversion and reconstruction of silver nanoprisms

A series of shapes of silver nanoplates were achieved by adjusting the concentration of citrate in the colloid in the photoinduced process. The local surface plasmon resonance (LSPR) of the silver nanoplates could be tuned gradually in a range from 740 to 440 nm. In contrast, the LSPR band can be photomediated again to the long wavelength region within 620-690 nm only by adding more citrate to the colloidal system. The initial silver nanoprisms converted to the discal shape under the light effect. In this conversion, the coupling effect of the plasmon resonance and the light source speeds up the photothermal reaction. Subsequently, the reconstruction of silver nanoprisms from the nanodisks took place in the presence of more citrate through the photoconversion.

The facet selectivity of inorganic ions on silver nanocrystals in etching reactions

The facet selectivity of the halide ions and chlorauric acid for several shaped silver nanocrystals is presented in this paper. Two inorganic ions show different representations when they are used for etching silver nanocrystals in the self-sacrificial template reaction. The morphological changes of the silver nanocrystals indicate that the halide ions prefer to etch the (110) facets of silver nanocrystals, while in the chlorauric acid etching reaction, gold first modifies the (110) facets and then lets chlorauric acid etch the (111) facets instead. The selective facet etching on individual nanoparticles in the solution phase has crucial significance in the control-synthesis of nanocrystals and the facet asymmetric reaction.

Real-time, in-situ, extinction spectroscopy studies on silver-nanoseed formation

In this paper, real-time extinction spectroscopy was employed to analyze in situ the fast formation process of silver seeds. The influencing factors for silver-seed formation, including the concentration of the reducer (NaBH 4), the amount of stabilizer (citrate), and the addition procedure of NaBH4, were evaluated. The configuration of the surface plasmon resonance (SPR) spectra of silver nanoparticles, which reflected the morphology of the produced silver seeds, was found to be distinctly affected by the NaBH4 concentration. Homogeneous silver nanoparticles were obtained when the added NaBH4 was lower in concentration than 2.00 mM. In contrast, higher concentrations of reducing agent (>3.00 mM NaBH4) resulted in uneven silver nanoparticles. Mie theory was applied to clarify the correlation of the SPR and the size of the silver seeds. Repeated additions of a small amount of the reducing agent could increase the monodispersity and isotropy of silver seeds. Real-time extinction spectroscopy is a convenient technique that achieves the in-situ and nondestructive measurement of intermediates in the formation process of silver nanoseeds.

Strong population genetic structure and its management implications in the mud carp Cirrhinus molitorella, an indigenous freshwater species subject to an aquaculture and culture-based fishery

This study investigated population genetic structure and diversity of mud carp Cirrhinus molitorella, a species widely used in aquaculture and culture-based fisheries in China and Mekong River riparian countries. Seven newly developed and one published microsatellite DNA markers were used to analyse samples from six wild locations, four hatchery broodstocks and one farmed site from the Mekong, Red and Pearl Rivers. Significant genetic structure was detected in C. molitorella, with isolation-by-distance being a strong force in the Mekong. Pair-wise F_ST, Fisher's exact tests for population differentiation, permutation tests and individual-based structure analysis all support the recognition of a sample originating from Toul Krasaing Lake (Cambodia) and one between Kratie and Stung Treng (Cambodia) as distinct from the remainder of the sampled range. Samples from the main upper Mekong and the Nam Khan River were significantly differentiated, but on a time scale inferred to be short (i.e. by genetic drift, not sufficient for evolution of new microsatellite alleles). The Mekong stock of C. molitorella was strongly differentiated from those from the Red and Pearl Rivers, inferred to be on an evolutionary time scale. Finer-scale sampling is warranted to further improve the understanding of genetic interactions among fish from the Mekong and its tributaries. Detailed studies on the ecology of C. molitorella (e.g. migration pathways and preferred spawning habitats) would provide useful information to explain the patterns of genetic structure detected here, and deepen insights about evolutionary distinctiveness of the population units.

Coloration of cotton fibers with anisotropic silver nanoparticles

Anisotropic silver nanoparticles were assembled on cotton fibers to realize the coloration of cotton. The assembly of silver nanoparticles on fibers was achieved by linking of poly(diallyldimethylammonium chloride) (PDDA) at room temperature. The silver nanoparticle treated cotton showed different colors because of localized surface plasmon resonance (LSPR) property of silver nanoparticles. The coloration was completed through electrostatic interaction between the PDDA treated cotton surface and the anisotropic silver nanoparticles in the reaction system. Scanning electron microscopy (SEM) characterization demonstrated that the morphologies of silver nanoparticles remained unchanged during the coloration process, so the treated cotton inherited the LSPR optical features of silver nanoparticles. Moreover, the cotton colorated with silver nanoparticles showed reasonably good color fastness to washing, which will facilitate the practical application of this coloration process.

A resonance tunable and durable LSPR nano-particle sensor : AL2O3 capped silver nano-disks

Localized surface plasmon resonance (LSPR) biosensors are employed to detect target biomolecules which have particular resonance wavelengths. Accordingly, tunability of the LSPR wavelength is essential in designing LSPR devices. LSPR devices employing silver nano-particles present better efficiencies than those using other noble metals such as gold; however, silver nano-particles are easily oxidized when they come in contact with liquids, which is inevitable in biosensing applications. To attain both durability and tunabilty in a LSPR biosensor, this paper proposes alumina (AL₂O₃) capped silver nano-disks. It is shown that through controlling the thickness of the cap, the LSPR resonance frequency can be finely tuned over a wide range; and moreover, the cap protects silver nano-particles from oxidation and high temperature.

The rise of the 'silver surfer' : online social networking and social inclusion for older adults

As the proportion of older adults continues to grow in many Western countries, there are increasing concerns about how to meet their needs. Ensuring social connectedness and inclusion is one way to support older adults’ wellbeing. Online social networking has become common place amongst younger age groups, suggesting its possible usefulness for older adults, in order to combat isolation and loneliness. Some quantitative studies have already explored the amount and degree of online social networking amongst older adults. To add further understanding of how older adults experience social inclusion via the internet, the current qualitative study aimed to explore older adults’ subjective experience of online social networking. Findings demonstrated a number of supports and barriers to social inclusion which reflect barriers to social inclusion of older adults in the non-virtual world. Recommendations to support social inclusion of isolated older adults via online social networking are suggested.

Impact of fermented mulberry leaf and fish offal in diet formulation of Indian major carp (Labeo rohita)

Large quantities of fish offal and mulberry leaf are generated globally. The present study aimed to understand their potential utilization in aqua diet formulation, after proper fermentation, as raw materials to replace fish meal in Indian major carp (Labeo rohita) compounded diet. Fish offal meal (FOM) and mulberry leaf meal (MLM) were used in a 2 × 3 factorial design, to evaluate (i) two different fermented mixtures with the inclusion of both FOM and MLM or only MLM and (ii) to replace three different level of dietary fishmeal: 50, 75 or 80 %. An indoor trial, to evaluate diet intake and digestibility and an outdoor trial to evaluate growth performances were impended in Indian major carp fingerlings. The results showed that FOM and MLM are promising raw materials that can be successfully used in the formulation of diet for the Indian major carp. Specifically, the addition of a proper amount of MLM in the fermentation of FOM produced a fermented mixture that could successfully replace up to 80 % of FM in the diet formulation.

Acceleration effect of reduced graphene oxide on photoinduced synthesis of silver nanoparticles

The photoinduced growth reaction of silver nanoparticles was accelerated by reduced graphene oxide (RGO) produced from graphene oxide (GO) during the light irradiation process in aqueous solution. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy demonstrated that RGO was generated in the photoinduced process. The acceleration effect of RGO was investigated through monitoring the extinction spectra of silver nanoparticles during the synthesis process. Moreover, transmission electron microscopy (TEM) was employed to characterize the evolution of morphologies of silver nanoparticles at different irradiation times to demonstrate the effect of RGO. The results indicate that RGO accelerates the photoinduced synthesis of silver nanoparticles. It is proposed that the acceleration effect of RGO on the photoinduced reaction is attributed to the particular property of high electronic conductivity

Shape evolution of silver nanoplates through heating and photoinduction

Shape conversions of silver nanoplates were realized by heating and subsequent light irradiation. The initial silver nanoprisms were transformed into silver nanodisks gradually in the process of heating, which was possibly achieved through dissolving and readsorption of silver atoms on the surface of silver nanoplates. Subsequently, under light irradiation, the heating induced silver nanodisks were reversed to silver nanoprisms in the same solution. The dissolved oxygen was found to play a pivotal role in the shape conversion from nanoprism to nanodisk. In addition to heating, deionized water could induce the shape conversion of silver nanoplates when it was added to precipitate of the initial silver nanoprisms after centrifugation. Citrate in solution is essential to the photoinduced shape conversion process. Transmission electron microscopy (TEM) and extinction spectroscopy results demonstrated that localized surface plasmon resonance (LSPR) properties of silver nanoplates were effectively tuned through shape conversion.