Jiajia Ning

Facile Synthesis of Tin Oxide Nanoflowers: A Potential High-Capacity Lithium-Ion-Storage Material

A facile and reproducible approach was reported to synthesize nanoparticle-attached SnO nanoflowers via decomposition of an intermediate product Sn6O4(OH)4. Sn6O4(OH)4 formed after introducing water into the traditional nonaqueous reaction, and then decomposed to SnO nanoflowers with the help of free metal cations, such as Sn2+, Fe2+, and Mn2+. This free cation-induced formation process was found independent of the nature of the surface ligand. It was demonstrated further that the as-prepared SnO nanoflowers could be utilized as good anode materials for lithium ion rechargeable batteries with a high capacity of around 800 mA h g(-1), close to the theoretical value (875 mA h g(-1)).

Recent advances in IV–VI semiconductor nanocrystals: synthesis, mechanism, and applications

This review is focused on the recent developments of the synthesis, mechanism and applications of IV–VI semiconductor nanocrystals (NCs), including germanium-, tin- and lead-based chalcogenides NCs. First of all, we systematically introduce a series of investigations on the preparation with controllable size and shape via a wide variety of methods. Corresponding growth mechanisms are also discussed. Moreover, the promising potential of IV–VI semiconductor NCs as building blocks with respect to energy, sensors and catalysis is highlighted. For the purpose of enhancing the performance to satisfy the practical applications, tailored nanocomposites by combining noble metals or graphene etc. are further developed. Finally, we present some concluding remarks and perspectives for future developments. We hope this article can provide researchers with the key snapshots of the recent advances and the future challenges, thus achieving a great progress in IV–VI semiconductor NCs.

Shape and size controlled synthesis and properties of colloidal IV–VI SnSe nanocrystals

Colloidal IV–VI SnSe nanocrystals with small and uniform size distribution were synthesized by a facile and phosphine-free method. Simple Sn6O4(OH)4 was introduced as a tin precursor to synthesize the SnSe nanocrystals. By changing the reaction temperature and Sn/Se molar ratio, SnSe nanocrystals with different shapes and sizes were achieved. The influence of reaction temperature and Sn/Se molar ratio to the shape and size of SnSe nanocrystals has been discussed detail. Similar to other IV–VI tin chalcogenides, SnSe shows potential as energy storage material. The performance of SnSe nanocrystals as an anode material for lithium ion batteries has been investigated. A mechanism for SnSe as anode material has been proposed based on its performance. The influence of the shape and size of the SnSe nanocrystals on the performance of lithium ion batteries has been discussed in detail.

One-step solution synthesis of bismuth sulfide (Bi2S3) with various hierarchical architectures and their photoresponse properties

In this paper, we introduce a facile and phosphine-free one-step solution method to synthesize size- and shape-controlled bismuth sulfide (Bi2S3) with hierarchical architectures. Changing variables, such as the reaction temperature, the ratio of precursors, and the concentration of oleic acid were observed to influence the resultant shape of Bi2S3 microstructures. For the formation of Bi2S3 hierarchical architectures, the crystal splitting growth mechanism played the dominant role. The absorption spectra were recorded at room temperature, which revealed that the obtained Bi2S3 product was a direct band gap semiconductor and the band gap Eg was estimated to be about 1.9 eV. Furthermore, the I–V characteristics of the Bi2S3-based device show a significant increase by ca. 1 order of magnitude compared with the dark state, indicating an enhanced conductivity and high sensitivity. The response and decay times are estimated to be about 0.5 and 0.8 s, respectively, which are short enough for it to be an excellent candidate for high-speed and high-sensitivity photodetectors or optical switches. Thus the Bi2S3 hierarchies as building blocks may offer the potential for monolithic, low-cost and large-scale integration with CMOS electronics.

Solution synthesis of copper selenide nanocrystals and their electrical transport properties

In this paper, we developed a one-pot solution strategy to synthesize copper selenide NCs with controllable shape and structure. By changing the precursors in the reaction, copper selenide NCs (Cu2−xSe nanoparticles, nanorods and CuSe nanoplates) with various morphologies could be achieved. We proposed a possible mechanism to explain the influence of precursors on the shape of copper selenide NCs and we found that the chemical activities of precursors played key roles in the morphologies and crystal structures of the final products. Moreover, the electrical transport properties of as-prepared products were investigated. The morphologies of copper selenide NCs have a great influence on the electrical transport properties. The copper selenide NCs with nanorods display the best electrochemical performance compared with the other two types. We believe that copper selenide NCs would be promising candidates for electrical transport materials.

Synthesis of narrow band gap SnTe nanocrystals: nanoparticles and single crystal nanowires via oriented attachment

SnTe nanocrystals with different shapes and sizes are synthesized by a simple and facile method. The length of the fatty chain in amine has an important effect on the shape and size of SnTe nanocrystals. When oleylamine (OLA) is used as ligand, SnTe nanoparticles with size of 4 nm and high crystallinity are produced. However, when octylamine (OTA) is used as ligand, larger SnTe nanoparticles with low crystallinity are achieved, which would transform into single crystal SnTe nanowires with increasing reaction time. The driving force of shape evolution of SnTe nanocrystals is reducing the high surface free energy. An oriented attachment mechanism is proposed to explain the transition from nanoparticles to nanowires, and oriented attachment of nanoparticles to single crystal nanowires is proposed to reduce the interface energy by the greatest amount.

Synthesis, optical properties and growth process of In2S3 nanoparticles

Cubic beta-In(2)S(3) nanoparticles (NPs) have been synthesized by a simple and facile way, which is 6 nm in size. Absorption and emission spectra of In(2)S(3) NPs show obvious blue peak shift compared to band gap of bulk In(2)S(3), indicating the strong quantum size confinement effect. The fluorescence quantum yield of In(2)S(3) NPs is found to be 10%. During the synthesis process, the absorption spectra have no peak shift, which is responding to transition from valence band to the conduction band levels. This absorption spectra show that the nucleation and growth process of In(2)S(3) NPs is very quick. The PL lifetime spectra and time resolved spectra give two emission processes in In(2)S(3) NPs, which would be excitonic recombination and electron-hole recombination via defects levels. The blue shift of emission peaks show the emission process in In(2)S(3) NPs is from mainly electron-holes recombination via defects levels to excitonic recombination. The Stokes shift becomes smaller which is mainly contributed by blue shift of emission and smaller contribution from the UV-Vis absorption. The absorption and emission spectra show the size and crystallinity of In(2)S(3) NPs have no changes (HRTEM images provide enough proofs); however the surface-related defects changed greatly in the reaction process.

ZnS nanocrystals and nanoflowers synthesized by a green chemistry approach: Rare excitonic photoluminescence achieved by the tunable molar ratio of precursors

In the present work, we demonstrated a simple and green synthesis route for shape-controlled ZnS nanocrystals, where only environmentally benign chemicals, namely sulfur, zinc oxide and olive oil, were employed. By controlling the experimental conditions, we were able to tune the band edge and trap state photoluminescences of ZnS nanocrystals and obtain pure excitonic photoluminescence that was rarely observed in literature. The trap state emission was derived from sulfur vacancies and would be eliminated when an excess of sulfur was used during the synthesis. Additionally, the morphology of ZnS nanocrystals could be tuned to appear like flowers, where the formation mechanism was systematically discussed.

Synthesis of doped zinc blende-phase InSe:M (M = Fe and Co) nanocrystals for diluted magnetic semiconductor nanomaterials

Zinc blende (ZB) structure InSe nanocrystals (NCs) doped with transition metals have been synthesized via a simple and facile synthetic route. Pure ZB InSe NCs are nanosheets, while InSe:Fe are nanoparticles 6–7 nm in size and InSe:Co are 10 nm nanoworms. Doped transition metal ions have an important influence on the shape and size of produced NCs, and the influence mainly occurs at the nucleation stage for the formation of NCs. Doped ZB-InSe NCs exhibit ferromagnetism, in particular, room-temperature ferromagnetic behavior for InSe:Co NCs was observed. This is the observation of magnetism in III–VI semiconductors. The doped metal ions and the induced defects are responsible for the generated ferromagnetism in doped ZB-InSe NCs.