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A separate two-step process with a rapid nucleation and a subsequent template-directed growth has been employed to synthesize uniform Ag nanoparticles, which avoids a classical un-refrained ripening process resulting in a wide size distribution. Some silver nanocrystallites prepared by this approach are particularly interesting because of their unusual nanostructures with multiple nanostripes caused by stacking faults. [Copyright &y& Elsevier]

Abstract In recent years, copper nanoclusters (Cu NCs) have attracted a great deal of research interests, because the fluorescence intensity will be significantly enhanced after they aggregate, which makes them an ideal material for constructing chemical sensors. The current Cu NCs based sensor researches focus mainly on the control of surface modification and aggregation conditions. Herein, we report a method for direct detection of Cu2+ ions through in situ cluster formation and aggregation. Glutathione was used as both reducing agent and stabilizing agent, while tetrahydrofuran as the poor solvent. When the analyte of Cu2+ ions were added to the mixed solution, they were reduced and aggregated to generate bright orange emission. The method is easy to operate and the reaction complete within 2 min. The detection limit for Cu2+ ions is as low as 0.17 μM. Based on these findings, we successfully achieved the determination of copper content in naturally occurring mineral. Therefore, the method reported here provides a convenient and sensitive way to perform qualitative analysis of Cu2+ ions. Highlights • A rapid and sensitive method for Cu2+ ions detection was developed. • The method was based on the formation and aggregation of Cu nanoclusters. • Glutathione was used as both reducing agent and stabilizing agent, while tetrahydrofuran as the poor solvent. • Proposed method has been successfully applied in naturally occurring mineral. [ABSTRACT FROM AUTHOR]

Thiolate-protected gold nanoclusters with high chemical stability are exploited extensively for fundamental research and utility in chosen applications. Here for the first time, the controlled destabilization of extraordinarily stable thiolated gold clusters for the growth of single-crystalline gold nanoparticles (AuNPs) is demonstrated, which was achieved simply via the oxidation of surface-protecting thiolates into disulfides by hydrogen peroxide under basic condition. By combining with our experimental observations over the entire destabilization and growth process, the new growth mechanism from clusters to AuNPs is revealed by density functional theory (DFT) calculations. It is found that the size of AuNPs decreases with the increase of hydrogen peroxide concentration due to the generation of more nuclei at the higher hydrogen peroxide concentrations. In addition, the preparation of AuNPs is tuned by changing the concentration of hydrogen peroxide, and they are self-assembled into microspheres via an evaporation-mediated process, which can induce strong plasmonic coupling between adjacent AuNPs for ultrasensitive surface-enhanced Raman scattering detection. The present work demonstrates a facile route to functionalize and engineer AuNPs via controlling the reaction conditions and the ratio of precursors, and thus bring new possibilities for using more clusters as precursors to construct novel nano/microstructures for various applications. [ABSTRACT FROM AUTHOR]

The real applications of Na 3 V 2 (PO 4 ) 3 cathode material for sodium batteries have been hindered by low-cost and facile synthesis method. Herein, we report a facile self-combustion method to synthesize Na 3 V 2 (PO 4 ) 3 nanoparticles coated with carbon shell (NVP/C). Using as the cathode, the NVP/C is capable of delivering the initial discharge and charge capacities of 100.72 and 111.3 mAh g −1 at the current of 0.1 C in a voltage of 2.5–3.8 V, and the capacity retention of the sample is approximately 95% of its initial specific capacity after 50th cycles. The first-principles simulation results show that the Na ions migration route prefers between two adjacent tetrahedral sites with the vacancy-hopping mechanism in a curved way, with the lowest activation energy of 0.292 eV. The diffusion coefficients D Na + at room temperature was also calculated as higher as 2.38 × 10 −9 cm 2 s −1 . The results suggest great potential of self-combustion synthesized NVP/C as cathode materials for Na-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: Trace penicilloic acid allergen frequently leads to various fatal immune responses to many patients, but it is still a challenge to directly discriminate and detect its residue in penicillin by a chemosensing way. Here, we report that silver-coated gold nanoparticles (Au@Ag NPs) exhibit a structure-selective hot-spot Raman enhancement capability for direct identification and detection of trace penicilloic acid in penicillin. It has been demonstrated that penicilloic acid can very easily link Au@Ag NPs together by its two carboxyl groups, locating itself spontaneously at the interparticle of Au@Ag NPs to form strong Raman hot-spot. At the critical concentration inducing the nanoparticle aggregation, Raman-enhanced effect of penicilloic acid is ~60,000 folds higher than that of penicillin. In particular, the selective Raman enhancement to the two carboxyl groups makes the peak of carboxyl group at C6 of penicilloic acid appear as a new Raman signal due to the opening of β-lactam ring of penicillin. The surface-enhanced Raman scattering (SERS) nanoparticle sensor reaches a sensitive limit lower than the prescribed 1.0‰ penicilloic acid residue in penicillin. The novel strategy to examine allergen is more rapid, convenient and inexpensive than the conventional separation-based assay methods. [Copyright &y& Elsevier]

We have developed a selective upconversion switching method for the ratiometric fluorescence detection of nitrite using upconversion nanoparticles (UCNPs) and an efficient nitrite reaction. The green emission (λem = 539 nm) of NaYF4:Yb3+,Er3+ nanoparticles can be selectively quenched by the neutral red (NR) dye due to the spectral overlap between the emission at 539 nm and the absorption of NR, while its red emission (λem = 654 nm) remains unchanged. Nitrite reacts specifically and strongly with NR to form diazonium salt and lose the diazonium group, which sharply decreases the absorption of NR. Thus, the green emission of NaYF4:Yb3+,Er3+ can be recovered by increasing the amount of nitrite, leading to visible color changes from red to orange-yellow and finally green under excitation at 980 nm. The increase in the ratio of emission intensities (I539/I654) is quantitatively correlated to the concentration of nitrite ions. Moreover, the developed method has been successfully applied to nitrite detection in real samples such as drinking water, natural water and meat foods. In particular, the upconversion sensors can efficiently avoid background optical interference and thus show potential for the detection of nitrite salts in complex samples. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the preparation of metsulfuron-methyl (MSM) imprinted polymer layer-coated silica nanoparticles toward analysis of trace sulfonylurea herbicides in complicated matrices. To induce the selective occurrence of surface polymerization, the polymerizable double bonds were first grafted at the surface of silica nanoparticles by the silylation. Afterwards, the MSM templates were imprinted into the polymer-coating layer through the interaction with functional monomers. The programmed heating led to the formation of uniform MSM-imprinted polymer layer with controllable thickness, and further improved the reproducibility of rebinding capacity. After removal of templates, recognition sites of MSM were exposed in the polymer layers. As a result, the maximum rebinding capacity was achieved with the use of optimal grafting ratio. There was also evidence indicating that the MSM-imprinted polymer nanoparticles compared with nonimprinted polymer nanoparticles had a higher selectivity and affinity to four structure-like sulfonylurea herbicides. Moreover, using the imprinted particles as dispersive solid-phase extraction (DSPE) materials, the recoveries of four sulfonylurea herbicides determined by high-performance liquid chromatography (HPLC) were 80.2–99.5%, 83.8–102.4%, 77.8–93.3%, and 73.8–110.8% in the spiked soil, rice, soybean, and corn samples, respectively. These results show the possibility that the highly selective separation and enrichment of trace sulfonylurea herbicides from soil and crop samples can be achieved by the molecular imprinting modification at the surface of silica nanoparticles. [ABSTRACT FROM AUTHOR]