Circularly polarized light emission and detection by chiral inorganic semiconductors.

Chiral inorganic semiconductors with high dissymmetric factor are highly desirable, but it is generally difficult to induce chiral structure in inorganic semiconductors because of their structure rigidity and symmetry. In this study, we introduced chiral ZnO film as hard template to transfer chirality to CsPbBr3 film and PbS quantum dots (QDs) for circularly polarized light (CPL) emission and detection, respectively. The prepared CsPbBr3/ZnO thin film exhibited CPL emission at 520 nm and the PbS QDs/ZnO film realized CPL detection at 780 nm, featuring high dissymmetric factor up to around 0.4. The electron transition based mechanism is responsible for chirality transfer.

Biologically Safe, Versatile, and Smart Bismuthene Functionalized with a Drug Delivery System Based on Red Phosphorus Quantum Dots for Cancer Theranostics.

Two-dimensional nanomaterials are attracting attention for cancer therapy. However, high toxicity, insensitivity to external stimuli and single therapeutic modality are still key issues hindering their clinical application. Therefore, the construction of a safe, intelligent and versatile nanocomposite is needed to meet clinical expectations. Herein, we developed a nanocomposite of Bi@RP-PEG-DOX with 2D bismuthene loaded with 0D red phosphorus quantum dots and DOX. The nanocomposite with DOX loading capacity (ca. 250 %) and photothermal conversion efficiency (ca. 54 %) showed both photothermal and photodynamic effects and a sensitive response of drug release to the acidic tumor microenvironment or NIR II laser irradiation. The nanocomposite exhibits good biosafety. Through the X-ray attenuation properties of bismuth, the nanocomposite serves as an excellent CT contrast agent, providing potential to perform CT-guided therapy.

Atomically thin two-dimensional ZnSe/ZnSe(ea)x van der Waals nanojunctions for synergistically enhanced visible light photocatalytic H2 evolution.

Two-dimensional (2D) photocatalysts have been widely studied due to their short charge carrier migration pathways and tunable electronic structures. Herein, a facile one-pot solvothermal process with ethylamine (ea) constructs a novel 2D nanojunction based on ZnSe. The ea molecules coordinate with Zn2+ to form 2D ZnSe(ea)x, where the consequent 2D ZnSe grows in an epitaxial way resulting in the self-assembled 2D/2D ZnSe/ZnSe(ea)x nanojunctions driven by van der Waals (VDW) force, which largely extend the absorption range. The atomic thickness of the 2D structure offers a short charge migration pathway, low electric resistance and rich active sites for the surface reaction of photocatalysis. All the above favorable factors work synergistically to reach a superior hydrogen evolution of 2875 µmol g-1 h-1 under visible light irradiation (≥420 nm) and a notable quantum yield of 64.5% at 450 nm, which are among the highest recorded values of non-noble metal photocatalysts.

Versatile Solution-Processed Synthesis of Two-Dimensional Ultrathin Metal Chalcogenides Following Frank-van der Merwe Growth.

Two-dimensional (2D) ultrathin metal chalcogenides represent a class of promising materials for various applications thanks to attractive physicochemical properties. However, a reliable pathway for fabricating ultrathin metal chalcogenides nanosheets, regardless of the bulk crystals of their 3D counterparts, still remains a challenge. Herein, we present a versatile solution-processed template synthesis strategy, in which a single molecular-level precursor anneals to ultrathin single-crystal nanosheets with the aid of lattice-matching templates, following the Frank-van der Merwe growth mode and featuring high quality, low cost, scalability, and processability. Following this strategy, Sb2S3, MoS2, and ZnS nanosheets are successfully prepared as representatives for materials whose bulk counterparts possess 1D, 2D, and 3D crystal structures, respectively, and the growth mechanism is confirmed by crystal mode analysis. As a proof-of-concept application, MoS2 and Sb2S3 nanosheets are used for gas sensor and flexible photodetector applications, respectively, which exhibit excellent performance. The method can also be easily extended to other ultrathin nanosheets like single metals, metal oxide, metal nitride, and heterostructures.

Highly Anisotropic Sb2 Se3 Nanosheets: Gentle Exfoliation from the Bulk Precursors Possessing 1D Crystal Structure.

2D materials, particularly those bearing in-plane anisotropic optical and electrical properties such as black phosphorus and ReS2 , have spurred great research interest very recently as promising building blocks for future electronics. However, current progress is limited to layered compounds that feature atomic arrangement asymmetry within the covalently bonded planes. Herein, a series of highly anisotropic nanosheets (Sb2 Se3 , Sb2 S3 , Bi2 S3 , and Sb2 (S, Se)3 ), which are composed of 1D covalently linked ribbons stacked together via van der Waals force, is introduced as a new member to the anisotropic 2D material family. These unique anisotropic nanosheets are successfully fabricated from their polymer-like bulk counterparts through a gentle water freezing-thawing approach. Angle-resolved polarized Raman spectroscopy characterization confirms the strong in-plane asymmetry of Sb2 Se3 nanosheets, and photodetection study reveals their high responsivity and anisotropic in-plane transport. This work can enlighten the synthesis and application of new anisotropic 2D nanosheets that can be potentially applied for future electronic and optoelectronic devices.

Bandgap tunable Csx(CH3NH3)1-xPbI3 perovskite nanowires by aqueous solution synthesis for optoelectronic devices.

To date, all the lead halide based full-inorganic or organic-inorganic hybrid perovskites have been synthesized from organic solvent, such as N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), by a solution method. Herein, water has been utilized as a 'green' solvent to develop an efficient synthetic route to grow various kinds of lead halide perovskite nanowires (NWs). By controlling the proportion of the hybrid cations, Csx(CH3NH3)1-xPbI3 perovskite NWs were successfully synthesized. Every Csx(CH3NH3)1-xPbI3 perovskite NW demonstrated single crystal characteristics with uniform stoichiometric element distribution. Because of the controllable cation composition, the NW bandgaps could be finely tuned from 1.5 to 1.7 eV. Transient photoluminescence spectra showed superior NW quality when compared with those of the conventional DMF-based NWs. Based on the abovementioned high quality single Cs0.5(CH3NH3)0.5PbI3 perovskite NW, a reliable single-NW photodetector was fabricated to investigate the optoelectronic application. It demonstrated a responsivity of 23 A/W, exceeding most of the reported values in the perovskite nanowire photoconductive detectors, and the shot-noise normalized detectivity was 2.5 × 1011 Jones comparable to the parameters of the commercial silicon-based nanowires. The green and robust synthesis method, finely tunable NW bandgaps, and superior optoelectronic properties are expected to open a new door for the development of perovskite optoelectronic devices.

Facile synthesis of diverse graphene nanomeshes based on simultaneous regulation of pore size and surface structure.

Recently, graphene nanomesh (GNM) has attracted great attentions due to its unique porous structure, abundant active sites, finite band gap and possesses potential applications in the fields of electronics, gas sensor/storage, catalysis, etc. Therefore, diverse GNMs with different physical and chemical properties are required urgently to meet different applications. Herein we demonstrate a facile synthetic method based on the famous Fenton reaction to prepare GNM, by using economically fabricated graphene oxide (GO) as a starting material. By precisely controlling the reaction time, simultaneous regulation of pore size from 2.9 to 11.1 nm and surface structure can be realized. Ultimately, diverse GNMs with tunable band gap and work function can be obtained. Specially, the band gap decreases from 4.5-2.3 eV for GO, which is an insulator, to 3.9-1.24 eV for GNM-5 h, which approaches to a semiconductor. The dual nature of electrophilic addition and oxidizability of HO(•) is responsible for this controllable synthesis. This efficient, low-cost, inherently scalable synthetic method is suitable for provide diverse and optional GNMs, and may be generalized to a universal technique.

Scalable salt-templated synthesis of two-dimensional transition metal oxides.

Two-dimensional atomic crystals, such as two-dimensional oxides, have attracted much attention in energy storage because nearly all of the atoms can be exposed to the electrolyte and involved in redox reactions. However, current strategies are largely limited to intrinsically layered compounds. Here we report a general strategy that uses the surfaces of water-soluble salt crystals as growth templates and is applicable to not only layered compounds but also various transition metal oxides, such as hexagonal-MoO3, MoO2, MnO and hexagonal-WO3. The planar growth is hypothesized to occur via a match between the crystal lattices of the salt and the growing oxide. Restacked two-dimensional hexagonal-MoO3 exhibits high pseudocapacitive performances (for example, 300 F cm(-3) in an Al2(SO4)3 electrolyte). The synthesis of various two-dimensional transition metal oxides and the demonstration of high capacitance are expected to enable fundamental studies of dimensionality effects on their properties and facilitate their use in energy storage and other applications.

Hydrazine solution processed Sb2S3, Sb2Se3 and Sb2(S(1-x)Se(x))3 film: molecular precursor identification, film fabrication and band gap tuning.

Sb2(S(1-x)Se(x))3 (0 ≤ x ≤ 1) compounds have been proposed as promising light-absorbing materials for photovoltaic device applications. However, no systematic study on the synthesis and characterization of polycrystalline Sb2(S(1-x)Se(x))3 thin films has been reported. Here, using a hydrazine based solution process, single-phase Sb2(S(1-x)Se(x))3 films were successfully obtained. Through Raman spectroscopy, we have investigated the dissolution mechanism of Sb in hydrazine: 1) the reaction between Sb and S/Se yields [Sb4S7](2-)/[Sb4Se7](2-) ions within their respective solutions; 2) in the Sb-S-Se precursor solutions, Sb, S, and Se were mixed on a molecular level, facilitating the formation of highly uniform polycrystalline Sb2(S(1-x)Se(x))3 thin films at a relatively low temperature. UV-vis-NIR transmission spectroscopy revealed that the band gap of Sb2(S(1-x)Se(x))3 alloy films had a quadratical relationship with the Se concentration x and it followed the equation Eg(x) = 0.118x(2) - 0.662x + 1.621eV, where the bowing parameter was 0.118 eV. Our study provides a valuable guidance for the adjustment and optimization of the band gap in hydrazine solution processed Sb2(S(1-x)Se(x))3 alloy films for the future fabrication of improved photovoltaic devices.