Novel closed-cycle reaction mode for totally green production of Cu_(1.8)Se nanoparticles based on laser-generated Se colloidal solution

Non-stoichiometric copper selenide(Cu_(2-x)Se,x=0.18~0.25)nanomaterials have attracted extensive attentions due to their excellent thermoelectric,optoelectronic and photocatalytic performances.However,efficient production of Cu_(2-x)Se nanoparticles(NPs)through a green and convenient way is still hindered by the inevitable non-environmentally friendly operations in common chemical synthesis.Herein,we initially reveal the coexistence of seleninic acid content and elemental selenium(Se)NPs in pulsed laser-generated Se colloidal solution.Consequently,we put forward firstly a closedcycle reaction mode for totally green production of Cu_(1.8)Se NPs to exclude traditional requirements of high temperature and toxic precursors by using Se colloidal solution.In such closed-cycle reaction,seleninic acid works as the initiator to oxidize copper sheet to release cuprous ions which can catalyze the disproportion of Se NPs to form Se O_(3)^(2-)and Se^(2-)ions and further produce Cu_(2-x)Se NPs,and the by-product SeO_(3)^(2-)ions promote subsequent formation of cuprous from the excessive Cu sheet.In experiments,the adequate copper(Cu)sheet was simply dipped into such Se colloidal solution at 70℃,and then the stream of Cu_(1.8)SeNPs could be produced until the exhaustion of selenium source.The conversion rate of Se element reaches to more than 75%when the size of Se NPs in weakly acidic colloidal solution is limited between 1 nm and 50 nm.The laser irradiation duration shows negative correlation with the size of Se NPs and unobvious impact to the p H of the solution which both are essential to the high yield of Cu_(1.8)SeNPs.Before Cu sheet is exhausted,Se colloidal solution can be successively added without influences to the product quality and the Se conversion rate.Such green methodology positively showcases a brand-new and potential strategy for mass production of Cu_(2-x)Se nanomaterials.

Colloidal CsPbBr3 perovskite nanocrystal films as electrochemiluminescence emitters in aqueous solutions

Perovskite nanocrystals （NCs）, which have emerged as a new class of phosphors with superb luminescence properties and bandgaps that can be easily tuned using chemical methods, have generated tremendous interest for a wide variety of applications where colloidal quantum dots have been very successful as carrier sources. In this study, self-assembled films of CsPbBr3 NCs were produced via drop casting of colloidal NCs onto glassy carbon electrodes （GCEs） to form an NC film-modified electrode. The possible fabrication process of the CsPbBr3 NCs films was discussed. We further studied the anodic electrochemiluminescence （ECL） behavior of the perovskite CsPbBr3 NCs film using cyclic voltammetry with tripropylamine （TPA） as a coreactant, and a possible ECL mechanism was proposed. Briefly, TPA was oxidized to produce strongly reducing radical spedes, which can react with electrochemically oxidized CsPbBr3 NCs to generate excited CsPbBr3 NCs＊ capable of light emission. The relative stability of the ECL emission of the CsPbBr3 NC films under aqueous conditions was also investigated, and it was found that they showed operational stability over the first three hours, indicating suitable reliability for application as sensing materials. The results suggested that semiconducting perovskite NCs have great potential for application in the ECL field.

Pd/Ag nanosheet as a plasmonic sensing platform for sensitive assessment of hydrogen evolution reaction in colloid solutions

A nanoplasmonic hydrogen-sensing system based on palladium/silver nanosheets （Pd/Ag NSs） was developed and used for sensitive assessment of the hydrogen evolution reaction （HER） in colloid solutions. As a model HER system, the semiconductor CdS/CdSe core/shell quantum dot （QD）-based hydrogen-producing colloidal system was used, and the HER performances of QDs with two different surface coatings were assessed in this study. In the sensing system, the photocatalytically generated hydrogen reacts with Pd/Ag NSs, resulting in a gradual red-shift of localized surface plasmon resonance, which to a certain degree is almost linearly proportional to the amount of hydrogen generated. Such a nanoplasmonic hydrogen sensing platform would be useful as an alternative for optical assessment and fast selection of a highly efficient and cost-effective solar hydrogen generation system for practical applications.

Tunable order in colloids of hard magnetic hexaferrite nanoplatelets

Structural ordering in the concentrated magnetic colloids containing 50×5 nm hard magnetic disc-like SrFe_(12)O_(19) nanoparticles was investigated by cryogenic scanning electron microscopy,optical microscopy,magnetic measurements,and small-angle X-ray scattering.It was revealed that macroscopically homogeneous magnetic liquid consists of dynamic threads of stacked nanoparticles.The threads align into quasiperiodic arrays with the distances between individual threads of a few micrometers.They also can form pseudodomain structures with -90°domain boundaries realized through T-type thread interconnects.The effects of magnetic attraction and electrostatic repulsion on the equilibrium interplatelet distance in the threads were studied.It was demonstrated that this distance can be tuned by the control of the particles charge and electric double layer screening from Stern layer thickness(-1 nm)to tens of nanometers.It was shown that the permanent magnetic field is not able to cause any structural changes in the ordered magnetic liquid phase,while alternating field draws particles apart by their vibrations.External variation of interparticle distance up to 6%was achieved using an alternating magnetic field of low intensity.Experimental data were complemented by the theoretical models of screened electrostatic interactions between spherical and platelike magnetic particles.The last model provides good predictive power and correlates with the experimental data.The stabilization energy of the condensed phase in the order of 1-10 kBT was derived from the model.An approach allows controlling of an equilibrium interparticle distance and interparticle distance distribution by adjusting the magnetization and surface charge of the particles as well as the ionic strength of the solvent.