Fabrication of CuInZnS/ZnS Quantum Dot Microbeads by a Two-Step Approach of Emulsification-Solvent Evaporation and Surfactant Substitution and Its Application for Quantitative Detection

CuInS2 quantum dots (CIS QDs) are considered to be promising alternatives for Cd-based QDs in the fields of biology and medicine. However, high-quality hydrophobic CIS QDs are difficult to be transferred to water due to their 1-dodecylmercaptan (DDT) ligands. Therefore, the fluorescence and stability of the prepared aqueous CIS QDs is not enough to meet the requirement for sensitive detection. Here, as large as 13 nm CuInZnS/ZnS QDs with DDT ligands were first synthesized, and then, CuInZnS/ZnS microbeads (QBs) containing thousands of QDs were successfully fabricated by a two-step approach of emulsion-solvent evaporation and surfactant substitution. Through emulsion-solvent evaporation, the CuInZnS/ZnS QDs formed microbeads in the microemulsion with dodecyl trimethylammonium bromide (DTAB), and the Förster resonance energy transfer (FRET) has been effectively overcome. Then, CO-520 was introduced to substitute DTAB to improve the stability and water solubility. Lastly, the microbeads were coated with a SiO2 shell and carboxylated. Subsequently, the constructed QBs (∼210 nm) were used as labels in a fluorescence immunosorbent assay (FLISA) for quantitative detection of heart type fatty acid binding protein (H-FABP), and the limit of detection was 0.48 ng mL-1, which indicated a greatly improved detection sensitivity compared to that of the Cd-free QDs. The highly fluorescent and stable CuInZnS/ZnS QBs will have great application prospects in many biological fields.

Role of Anions in the Synthesis and Crystal Growth of Selected Semiconductors

The ideal methods for the preparation of semiconductors should be reproducible and possess the ability to control the morphology of the particles with monodispersity yields. Apart from that, it is also crucial to synthesize a large quantity of desired materials with good control of size, shape, morphology, crystallinity, composition, and surface chemistry at a reasonably low production cost. Metal oxides and chalcogenides with various morphologies and crystal structures have been obtained using different anion metal precursors (and/or different sulfur sources for chalcogenides in particular) through typical synthesis methods. Generally, spherical particles are obtained as it is thermodynamically favorable. However, by changing the anion precursor salts, the morphology of a semiconductor is influenced. Therefore, precursors having different anions show some effects on the final forms of a semiconductor. This review compiled and discussed the effects of anions (NO₃⁻, Cl⁻, SO₄^2-, CH₃COO⁻, CH(CH₃)O⁻, etc.) and different sources of S^2- on the morphology and crystal structure of selected metal oxides and chalcogenides respectively.

Two-dimensional copper based colloidal nanocrystals: synthesis and applications

Two-dimensional (2D) semiconductor nanocrystals display unconventional physical and opto-electronic properties due to their ultrathin and unique electronic structures. Since the success of Cd-based photoemissive nanocrystals, the development of sustainable and low-cost nanocrystals with enhanced electronic and physical properties has become a central research theme. In this context, copper-based semiconductor 2D nanocrystals, the cost-effective and eco-friendly alternative, exhibit unique plasmonic resonance, transport properties, and high ionic conductivity beneficial for sensing, energy storage, conversion, and catalytic applications. This review summarizes recent progress in the colloidal synthesis, growth mechanisms, properties, and applications of 2D copper-based nanostructures with tunable compositions, dimensions, and crystal phases. We highlight the growth mechanisms concerning their shape evolution in two dimensions. We analyse the effectiveness of cation exchange as a tool to synthesize multinary nanocrystals. Based on the preparation of Cu-based chalcogenide and non-chalcogenide compositions, we discuss synthesis control achieved via colloidal approaches to allow dimension tunability, phase engineering, and plasmonic and thermoelectric property optimization. Furthermore, their potential in various applications of catalysis, energy storage, and sensing is reviewed. Finally, we address the current challenges associated with 2D Cu-based nanocrystal development and provide an outlook pertaining to unexplored research areas.

Recent research on the luminous mechanism, synthetic strategies, and applications of CuInS2 quantum dots

We discuss the synthesis and luminescence mechanisms of CuInS₂ QDs, the strategies to improve their luminous performance and their potential application in light-emitting devices, solar energy conversion, and the biomedical field.

Influence of halide ions on the structure and properties of copper indium sulphide quantum dots

In the synthesis of CuInS2 quantum dots (QDs), the halide ions present in the copper salts influence the QD growth and optical properties. X-ray absorption spectroscopy allowed rationalizing the halide incorporation in the lattice and the dependence of electronic properties of the material on the ion's polarizability and interaction with hydrophobic moieties.

Seed-mediated growth of heterostructured Cu1.94S-MS (M = Zn, Cd, Mn) and alloyed CuNS2 (N = In, Ga) nanocrystals for use in structure- and composition-dependent photocatalytic hydrogen evolution

Multinary copper-based chalcogenide nanocrystals (NCs) as light-driven photocatalysts have attracted extensive research interest due to their great potential for generating sustainable energy without causing environmental concerns. However, systematic studies on the growth mechanism and related photocatalytic activities involving different valent metal ions (either M²⁺ or N³⁺) as foreign cations and monoclinic Cu_1.94S NCs as the 'parent lattice' have rarely been carried out. In this work, we report an effective seed-mediated method for the synthesis of heterostructured Cu_1.94S-MS NCs (M = Zn, Cd and Mn) and alloyed CuNS₂ NCs (N = In and Ga). A typical cation exchange process took place prior to the growth of heterostructured NCs, while further inter-cation diffusion occurred only for the alloyed NCs. When compared with Cu_1.94S NCs, all the heterostructured Cu_1.94S-MS NCs and CuGaS₂ NCs showed enhanced photocatalytic activities toward hydrogen production by water splitting, owing to their tailored optical band gaps and energy level alignments. Although optically favored, CuInS₂ ANCs were not comparable to others due to their low conduction band minimum for the reduction of H₂O to H₂.

A General One-Pot Approach to Synthesize Binary and Ternary Metal Sulfide Nanocrystals

A general one-pot approach is developed to synthesize a series of binary metal sulfide nanocrystals (NCs) including PbS, Cu₂S, ZnS, CdS, Ag₂S, and ternary CuInS₂ and CdS:Cu(I) NCs. This synthetic approach involves thermal decomposition of the mixture of inorganic metal salts and n-dodecanethiol (DDT) without pre-synthesis of any organometallic precursors. In this method, layered metal-thiolate compound is formed at the beginning of the reaction and then this intermediate compound is decomposed into small particles, leading to further growth as the reaction time increases. The as-obtained CdS NCs exhibits a broad but weak surface-state emission, and the Cu(I) doping leads to a red-shift of the emission band due to the Cu(I)-related emission. It is expected that this one-pot approach can be extended to prepare multinary metal sulfide NCs.

From one-dimensional to two-dimensional wurtzite CuGaS2 nanocrystals: non-injection synthesis and photocatalytic evolution

Multinary copper-based chalcogenides exhibit significant performance in photocatalytic hydrogen evolution due to their suitable optical bandgap for visible light absorption and environmentally friendly character. Herein, high-quality wurtzite CuGaS2 (CGS) nanocrystals (NCs) were synthesized by using a one-step heating-up process without any injection, and the morphology could be tuned from one-dimensional (1D) to two-dimensional (2D) by precise choice of surface ligands and gallium precursors. The formation mechanism of CGS NCs was studied comprehensively by means of the temporal-evolution of the morphology, crystal structure and optical absorption results. The reaction started from djurleite Cu31S16 NCs, and then proceeded with the formation of Cu31S16-CGS heteronanostructures (HNS), and finally the transformation from HNS to monophasic CGS nanorods took place with prolonging of the synthesis time. The optical bandgap and the energy level of the different-dimensional CGS NCs exhibited a strong dependence on the morphology change, which correlated with the percentage of the exposed {001} and {100} facets. The theoretical calculation based on density functional theory (DFT) revealed that the (001) surface facilitated the charge transport rather than the (100) surface, which was consistent with the electrochemical impedance spectroscopy (EIS) results. As a result, the 2D CGS nanoplates with more exposed {001} facets exhibited an attractive photocatalytic hydrogen production activity under simulated solar illumination as compared to 1D and quasi-2D counterparts. This study demonstrates that control over the dimension of I-III-V group semiconductor NCs could lead to a significant improvement of the photocatalytic hydrogen evolution.

Formation of uniform carrot-like Cu31S16-CuInS2 heteronanostructures assisted by citric acid at the oil/aqueous interface

A simple two-phase strategy was developed to prepare Cu₃₁S₁₆-CuInS₂ heterostructures (HNS) at the oil/aqueous interface, in which the In(OH)₃ phase was often obtained in the products due to the reaction between indium ions and hydroxyl ions in the aqueous phase. To prevent the formation of the In(OH)₃ phase, citric acid was incorporated into the aqueous phase to assist in the synthesis of uniform carrot-like Cu₃₁S₁₆-CuInS₂ semiconductor HNS at the oil/aqueous interface for the first time. By manipulating the dosage of citric acid and Cu/In precursor ratios, the morphology of the Cu₃₁S₁₆-CuInS₂ HNS could be tailored from mushroom to carrot-like, and the presence of citric acid played a critical role in the synthesis of high-quality Cu₃₁S₁₆-CuInS₂ HNS, which inhibited the formation of the In(OH)₃ phase due to the formation of the indium(iii)-citric acid complex. The formation mechanism was studied by monitoring the morphology and phase evolution of the Cu₃₁S₁₆-CuInS₂ HNS with reaction time, which revealed that the Cu₃₁S₁₆ seeds were first formed and then the cation-exchange reaction directed the subsequent anisotropic growth of the Cu₃₁S₁₆-CuInS₂ HNS.

Observation of enhanced photocurrent response in M–CuInS2 (M = Au, Ag) heteronanostructures: phase selective synthesis and application

We demonstrate the phase selective synthesis of M–CuInS₂ (M = Au and Ag) heteronanostructures and their enhanced photocurrent activity compared to that of pure CuInS₂.

Hierarchical architecture of CuInS2 microsphere thin films: altering laterally aligned crystallographic plane growth by Cd and V doping

Nano-flakes of self-assembled porous pristine and cadmium (Cd) and vanadium (V) doped copper indium disulphide (CuInS₂ (CIS)) microspheres are synthesized.

Synthesis and phase transition of wurtzite Cu3ZnInSnS6 nanodisks

Wurtzite Cu3ZnInSnS6 (CZITS) nanodisks were successfully synthesized according to rational design via a hot-injection method. Their suitable band gap and photoresponsive behavior indicate great potential application in solar cells. The structure of CZITS transforms to a tetragonal type after annealing, which is accompanied by grain growth.