Kinetically controlled synthesis of wurtzite ZnS nanorods through mild thermolysis of a covalent organic-inorganic network

Detailed insights into the formation pathway of CdS and ZnS in solution: a multi-modal in situ characterisation approach

The high stability, high availability, and wide size-dependent bandgap energy of sulphidic semiconductor nanoparticles (NPs) render them promising for applications in optoelectronic devices and solar cells. However, the tunability of their optical properties depends on the strict control of their crystal structure and crystallisation process. Herein, we studied the structural evolution during the formation of CdS and ZnS in solution by combining in situ luminescence spectroscopy, synchrotron-based X-ray diffraction (XRD) and pair distribution function (PDF) analyses for the first time. The influence of precursor type, concentration, temperature and heating program on the product formation and on the bandgap or trap emission were investigated in detail. In summary, for CdS, single-source precursor (SSP) polyol strategies using the dichlorobis(thiourea)cadmium(II) complex and double-source precursor approaches combining Cd(CH₃COO)₂·2H₂O and thiourea led to the straightforward product at 100 °C, while the catena((m₂-acetato-O,O')-(acetate-O,O')-(m₂-thiourea)-cadmium) complex was formed at 25 and 80 °C. For ZnS, the reaction between Zn(CH₃COO)₂·2H₂O and thiourea at 100 °C led to the product formation after the crystallisation and dissolution of an unknown intermediate. At 180 °C, besides an unknown phase, the acetato-bis(thiourea)-zinc(II) complex was also detected as a reaction intermediate. The formation of such reaction intermediates, which generally remain undetected applying only ex situ characterisation approaches, reinforce the importance of in situ analysis for promoting the advance on the production of tailored semiconductor materials.

Synthesis of Polyaniline Supported CdS/CdS-ZnS/CdS-TiO2 Nanocomposite for Efficient Photocatalytic Applications

Photocatalytic degradation can be increased by improving photo-generated electrons and broadening the region of light absorption through conductive polymers. In that view, we have synthesized Polyaniline (PANI) with CdS, CdS-ZnS, and CdS-TiO₂ nanocomposites using the chemical precipitation method, characterized and verified for the photo-degradation of Acid blue-29 dye. This paper provides a methodical conception about in what way conductive polymers “PANI” enhances the performance rate of composite photocatalysts (CdS, CdS-ZnS and CdS-TiO₂). The nanocomposites charge transfer, molar ratio, surface morphology, particle size, diffraction pattern, thermal stability, optical and recombination of photo-generated charge carrier properties were determined. The production of nanocomposites and their efficient photocatalytic capabilities were observed. The mechanism of photocatalysis involved with PC, CZP and CTP nanocomposites are well presented by suitable diagrams representing the exchange of electrons and protons among themselves with supported equations. We discovered that increasing the number of nanocomposites in the membranes boosted both photocatalytic activity and degradation rate. CdS-Zinc-PANI (CZP) and CdS-TiO₂-PANI(CTP) nanocomposites show entrapment at the surface defects of Zinc and TiO₂ nanoparticles due to the demolition of unfavorable electron kinetics, and by reducing the charge recombination, greater photocatalytic activity than CdS-PANI (CP) with the same nanoparticle loading was achieved. With repeated use, the photocatalysts’ efficiency dropped very little, hinting that they may be used to remove organic pollutants from water. The photocatalytic activity of CZP and CTP photocatalytic membranes was greater when compared to CdS-PANI, which may be due to the good compatibility between CdS and Zinc and TiO₂, as well efficient charge carrier separation. PANI can also increase the split-up of photo-excited charge carriers and extend the absorption zone when combined with these nanoparticles. As a result, the development of outrageous performance photocatalysts and their potential uses in ecological purification and solar power conversion has been facilitated. The novelty of this article is to present the degradation of AB-29 Dye using nanocomposites with polymers and study the enhanced degradation rate. Few studies have been carried out on polymer nanocomposites and their application in the degradation of AB-29 dyes and remediation of water purposes. Nanoparticle CdS is a very effective photocatalyst, commonly used for water purification along with nanoparticle ZnS and TiO₂; but cadmium ion-leaching makes it ineffective for practical and commercial use. In the present work, we have reduced the leaching of hazardous cadmium ions by trapping them in a polyaniline matrix, hence making it suitable for commercial use. We have embedded ZnS and TiO₂ along with CdS in a polyaniline matrix and compared their photocatalytic activity, stability, and reusability, proving our nano-composites suitable for commercial purposes with enhanced activities and stabilities, which is a novelty. All synthesized nanocomposites are active within the near-ultraviolet to deep infrared (i.e., 340–850 nm). This gives us full efficiency of the photocatalysts in the sunlight and further proves the commercial utility of our nanocomposites.

Preparation of ZnS@N-doped-carbon composites via a ZnS-amine precursor vacuum pyrolysis route

ZnS/carbon nanocomposites have potential electrochemical applications due to their improved conductivity and more active sites through modification of the carbon materials. Herein, we report a facile method to synthesize the nanocomposites comprising ZnS nanoparticles and nitrogen-doped carbon (ZnS@NC). The inorganic–organic hybrid ZnS-amine material ZnS(ba) (ba = n-butylamine) is synthesized on a large scale by a reflux method, which effectively shortens the reaction time while maintaining the high yield compared with the solvothermal method. Then ZnS(ba) is used as precursor for obtaining ZnS@NC nanocomposites via a vacuum pyrolysis route, in which the content of carbon and nitrogen can be controlled by adjusting the pyrolysis temperature. Further, a series of ZnS-amine hybrid materials ZnS(ha), ZnS(en)_0.5 and ZnS(pda)_0.5 (ha = n-hexylamine; en = ethylenediamine; pda = 1,3-propanediamine) are synthesized and used as precursors for the preparation of ZnS@NC materials, indicating the universality of this method. Moreover, the as-synthesized ZnS@NC materials exhibit remarkable lithium storage performance with outstanding cycling stability, high-rate capability and remarkable pseudo-capacitance characteristics.

ZnS/N-doped-carbon nanocomposites exhibiting remarkable Li storage performance are facilely prepared through the temperature-controllable vacuum pyrolysis of various ZnS-amine precursors.

Blue-emitting and self-assembled thinner perovskite CsPbBr3 nanoplates: synthesis and formation mechanism

Low dimensional semiconductor nanomaterials show great promise for a variety of applications due to their size-dependent and excellent optoelectronic properties. In this work, we developed a strategy to synthesize uniform and very thin CsPbBr₃ perovskite nanoplates (NPls) by introducing additional metal bromides. The CsPbBr₃ NPls, self-assembled into a face-to-face stacked state, had a thickness of 4.4 nm (equal to only 2 monolayers, 2 MLs) and showed a maximum emission at 437 nm and a narrow FWHM of 14 nm. The formation mechanism of the CsPbBr₃ NPls by adding FeBr₃ was ascribed to the constrained growth of CsPbBr₃ nanocubes when the surface Cs⁺ ions were substituted by the protonated oleylammonium from the byproduct OLA-HBr.

Heavy-Metal-Free Colloidal Semiconductor Nanorods: Recent Advances and Future Perspectives

Quasi-1D colloidal semiconductor nanorods (NRs) are at the forefront of nanoparticle (NP) research owing to their intriguing size-dependent and shape-dependent optical and electronic properties. The past decade has witnessed significant advances in both fundamental understanding of the growth mechanisms and applications of these stimulating materials. Herein, the state-of-the-art of colloidal semiconductor NRs is reviewed, with special emphasis on heavy-metal-free materials. The main growth mechanisms of heavy-metal-free colloidal semiconductor NRs are first elaborated, including anisotropic-controlled growth, oriented attachment, solution-liquid-solid method, and cation exchange. Then, structural engineering and properties of semiconductor NRs are discussed, with a comprehensive overview of core/shell structures, alloying, and doping, as well as semiconductor-metal hybrid nanostructures, followed by highlighted practical applications in terms of photocatalysis, photodetectors, solar cells, and biomedicine. Finally, challenges and future opportunities in this fascinating research area are proposed.

Tribological Properties of ZnS(NH2CH2CH2NH2)0.5 and ZnS as Additives in Lithium Grease

The layered compound ZnS(NH2CH2CH2NH2)0.5 was evaluated as an additive in grease with different concentrations by using a four-ball tribometer. Results show that ZnS(NH2CH2CH2NH2)0.5 grease has good load bearing ability and excellent anti-wear properties. ZnS(NH2CH2CH2NH2)0.5 revealed better wear resistance than that of ZnS under all test conditions. The reason for this may be that the two-dimensional structure of ZnS(NH2CH2CH2NH2)0.5, with larger interspaces, facilitates an easier sliding process, improving the anti-wear performance. The mechanism was estimated through analysis of the worn surface with SEM, EDS, 3D, and XPS. XPS analysis results show that the tribofilm was mainly composed of FeS, ZnS, ZnO, FexOy, Feu(SO4)v, and ZnSO4. Owing to the simple synthetic method and superior tribological properties as a grease-based additive, ZnS(NH2CH2CH2NH2)0.5 holds great potential for use in demanding industrial applications in the future.

Synthesis and characterization of ZnS with controlled amount of S vacancies for photocatalytic H2 production under visible light

Controlling amount of intrinsic S vacancies was achieved in ZnS spheres which were synthesized by a hydrothermal method using Zn and S powders in concentrated NaOH solution with NaBH₄ added as reducing agent. These S vacancies efficiently extend absorption spectra of ZnS to visible region. Their photocatalytic activities for H₂ production under visible light were evaluated by gas chromatograph, and the midgap states of ZnS introduced by S vacancies were examined by density functional calculations. Our study reveals that the concentration of S vacancies in the ZnS samples can be controlled by varying the amount of the reducing agent NaBH₄ in the synthesis, and the prepared ZnS samples exhibit photocatalytic activity for H₂ production under visible-light irradiation without loading noble metal. This photocatalytic activity of ZnS increases steadily with increasing the concentration of S vacancies until the latter reaches an optimum value. Our density functional calculations show that S vacancies generate midgap defect states in ZnS, which lead to visible-light absorption and responded.

ZnO nanorods/ZnS·(1,6-hexanediamine)(0.5) hybrid nanoplates hierarchical heteroarchitecture with improved electrochemical catalytic properties for hydrazine

Novel hierarchical heteronanostructures of ZnO nanorods/ZnS·(HDA)0.5 (HDA = 1,6-hexanediamine) hybrid nanoplates on a zinc substrate are successfully synthesized on a large scale by combining hydrothermal growth (for ZnO nanorods) and liquid chemical conversion (for ZnS·(HDA)0.5 nanoplates) techniques. The formation of ZnS·(HDA)0.5 hybrid nanoplates branches takes advantage of the preferential binding of 1,6-hexanediamine on specific facets of ZnS, which makes the thickening rate much lower than the lateral growth rate. The ZnS·(HDA)0.5 hybrid nanoplates have a layered structure with 1,6-hexanediamine inserted into interlayers of wurtzite ZnS through the bonding of nitrogen. The number density and thickness of the secondary ZnS·(HDA)0.5 nanoplates can be conveniently engineered by variation of the sulfur source and straightforward adjustment of reactant concentrations such as 1,6-hexanediamine and the sulfur source. The fabricated ZnO/ZnS·(HDA)0.5 heteronanostructures show improved electrochemical catalytic properties for hydrazine compared with the primary ZnO nanorods. Due to its simplicity and efficiency, this approach could be similarly used to fabricate varieties of hybrid heterostructures made of materials with an intrinsic large lattice mismatch.

Synthesis, spectral and thermal studies of pyridyl adducts of Zn(ii) and Cd(ii) dithiocarbamates, and their use as single source precursors for ZnS and CdS nanoparticles

The synthesis and characterization of pyridyl adducts of Zn(ii) and Cd(ii) dtc: precursors to ZnS and CdS nanoparticles are reported.

YOF nano/micro-crystals: morphology controlled hydrothermal synthesis and luminescence properties

SEM images and multicolored down-conversion and up-conversion luminescence photographs of the YOF: Ln³⁺ nano/micro-structures.

Complex ZnO nanotree arrays with tunable top, stem and branch structures

Hierarchical tree-, mushroom- and cockscomb-like ZnO arrays with increasing branching order and complexities have been grown in situ on cheap zinc plates by a simple hydrothermal oxidation approach. Their morphology, crystal structure and orientation relationship are characterized by powder X-ray diffraction, scanning electron microscopy (SEM) and cross-sectional high-resolution transmission electron microscopy (HRTEM). The wurtzite ZnO arrays, growing mainly in the [0001] direction, show a special orientation relationship between the stem and the branch as well as a novel stem-branch boundary which might be attributed to the least mismatch between [symbol: see text] and (0002) lattice planes. The co-solvent ethylenediamine (en) was used to control the morphology and complexing of these complex ZnO nanostructures. Correspondingly, the physical properties of ZnO nanostructure assembly arrays were tuned and a stronger UV emission was observed with negligible emissions in the visible range, indicating the highly crystalline features of the complex ZnO micro-/nanostructured materials.

Fabrication of ZnS nanoparticle chains on a protein template

In the present study, we have exploited the properties of a fibrillar protein for the template synthesis of zinc sulfide (ZnS) nanoparticle chains. The diameter of the ZnS nanoparticle chains was tuned in range of ~30 to ~165 nm by varying the process variables. The nanoparticle chains were characterized by field emission scanning electron microscopy, UV-Visible spectroscopy, transmission electron microscopy, electron energy loss spectroscopy, and high-resolution transmission electron microscopy. The effect of incubation temperature on the morphology of the nanoparticle chains was also studied.

Shape-Controlled Synthesis of ZnS Nanostructures: A Simple and Rapid Method for One-Dimensional Materials by Plasma

In this paper, ZnS one-dimensional (1D) nanostructures including tetrapods, nanorods, nanobelts, and nanoslices were selectively synthesized by using RF thermal plasma in a wall-free way. The feeding rate and the cooling flow rate were the critical experimental parameters for defining the morphology of the final products. The detailed structures of synthesized ZnS nanostructures were studied through transmission electron microscope, X-ray diffraction, and high-resolution transmission electron microscope. A collision-controlled growth mechanism was proposed to explain the growth process that occurred exclusively in the gas current by a flowing way, and the whole process was completed in several seconds. In conclusion, the present synthetic route provides a facile way to synthesize ZnS and other hexagonal-structured 1D nanostructures in a rapid and scalable way.

Fabrication of ZnS nanoparticles and nanorods with cubic and hexagonal crystal structures: a simple solvothermal approach

ZnS nanoparticles and nanorods with control over their crystal structure are fabricated through a solvothermal approach by changing the solvent used for the synthesis. The synthetic approach is suitable to fabricate ZnS nanoparticles with various sizes by varying the synthesis temperatures. Quantum confinement phenomena are studied by tailoring the particle sizes for both wurtzite and sphalerite polymorphs of ZnS. Photoluminescence studies reveal that the surface states greatly influence the emissions from the nanostructures. Wurtzite nanoparticles exhibit band-edge related UV emission owing to the effective surface passivation by the ethylene glycol molecules used as the solvent for the synthesis. On the other hand, the photoluminescence spectra of the cubic nanoparticles are mainly dominated by their surface states. Some of the nanorod samples exhibited Zn-vacancy related green emissions along with the surface defect related blue emission band. It is also demonstrated that ZnS nanostructures could be easily doped with useful impurities via this synthesis approach to tailor their luminescent properties.

Highly uniform and monodisperse beta-NaYF(4):Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu3+ (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to 5D0-3 --> 7FJ (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively. When doped with 5% Tb3+ ions, the strong DC fluorescence corresponding to 5D4 --> 7FJ (J = 6, 5, 4, 3) transitions with 5D4 --> 7F5 (green emission at 544 nm) being the most prominent group that has been observed. In addition, under 980 nm laser excitation, the Yb3+/Er3+- and Yb3+/Tm3+-codoped beta-NaYF4 samples exhibit bright green and whitish blue up-conversion (UC) luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.

New Heterobimetallic and Polymeric Selenocarboxylates Derived from [M(SeC{O}Ph)4]- (M = Ga and In) as Molecular Precursors for Ternary Selenides

(Et3NH)[In(SeC{O}Ph)4].H2O (1) along with heterobimetallic and polymeric metal selenocarboxylates, namely [NaGa(SeC{O}Ph)4] (2), [K(MeCN)2Ga(SeC{O}Ph)4] (3), [NaIn(SeC{O}Ph)4] (4), [K(MeCN)2In(SeC{O}Ph)4] (5), [(Ph3P)2CuIn(SeC{O}Ph)4].CH2Cl2 (6), and [(Ph3P)2AgIn(SeC{O}Ph)4].CH2Cl2 (7), have been synthesized by incorporating either alkali metal ions (Na+ and K+) or group 11 metal ions (Cu(I) and Ag(I)) into the [M(SeC{O}Ph)4]- anion. Crystal structures determined by X-ray crystallography indicate that 3 and 5 have one-dimensional coordination polymeric structures while 6 and 7 have an M(mu-Se)2In (M = Cu, Ag) core. The thermal decomposition of these compounds except 4 lead to the formation of the corresponding metal selenides as confirmed by thermogravimetric analysis and in some cases by powder X-ray diffraction studies.

Selected-Control Hydrothermal Synthesis and Formation Mechanism of Monazite- and Zircon-Type LaVO4 Nanocrystals

Selective-controlled structure and shape of LaVO(4) nanocrystals were successfully synthesized by a simple hydrothermal method without the presence of catalysts or templates. It was found that tuning the pH of the growth solution was a crucial step for the control of the structure transformation, that is, from monoclinic (m-) to tetragonal (t-) phase, and morphology evolution of LaVO(4) nanocrystals. Further studies demonstrated that the morphology of the product had a strong dependence on the initial lanthanum sources. In the La(NO(3))(3) or LaCl(3) reaction system, pure t-LaVO(4) nanorods with uniform diameters about 10 nm could be obtained. But when using La(2)(SO(4))(3) as the lanthanum source, we can get t-LaVO(4) nanowiskers with broomlike morphology. The detailed systematic study had shown that a special dissolution-recrystallization transformation mechanism as well as an Ostwald ripening process was responsible for the phase control and anisotropic morphology evolution of the LaVO(4) nanocrystals. As a result, the controlled synthesis of m- and t-LaVO(4) not only has great theoretical significance in studying the polymorph control and selective synthesis of inorganic materials but also benefits the potential applications based on LaVO(4) nanocrystals owing to the unusual luminescent properties induced by structural transformation.

Generation and Optical Properties of Monodisperse Wurtzite-Type ZnS Microspheres

Monodisperse wurtzite-type ZnS microspheres have been prepared by using glutathione (GSH) as a sulfur source at low reaction temperatures ranging from 160 to 210 degrees C. The diameter of the ZnS microspheres can be tuned from approximately 254 to approximately 597 nm by changing the reaction parameters such as temperature, molar ratio of reactants (GSH/Zn2+), and reaction medium (ethylenediamine or ammonia). Our results demonstrate that monodentate amines (ammonia) play the same role as that of bidentate amines (ethylenediamine) in the formation of the wurtzite-type ZnS microspheres. The formation process of the monodisperse ZnS microspheres consists of a GSH-dominated nucleation process and an amine-dominated assembly process. The as-synthesized monodisperse ZnS microspheres readily self-assemble into ordered hexagonal patterns and thus have potential applications as colloidal crystalline materials. Blue fluorescence emission peaks at 415 and 466 nm in wavelength, attributed to deep-trap emission, are observed at room temperature.

Solvothermal Synthesis and Photoluminescent Properties of ZnS/Cyclohexylamine: Inorganic−Organic Hybrid Semiconductor Nanowires

An inorganic-organic hybrid semiconductor, ZnS/CHA (CHA = cyclohexylamine) nanocomposites was successfully synthesized via a solvothermal method using CHA as solvent, which yielded uniform and ultralong nanowires with widths of 100-1000 nm and lengths of 5-20 microm. Changing the reaction conditions could alter the morphology and optical properties of the nanocomposites. The periodic layer subnanometer structures were identified by high-resolution transmission electron microscopy (HR-TEM) images, with thickness of approximately 2 nm. The composites exhibited a very large blue-shift in their optical absorption edge as well as an exciton excitation band due to a strong quantum confinement effect caused by the internal subnanometer-scale structures. The pure hexagonal wurtzite ZnS nanowires were also obtained by extracting the ZnS/CHA nanocomposites with dimethyl formamide (DMF). In addition, the luminescent properties of exciton and defect-related transitions in different samples of ZnS/CHA were discussed in detail.

One-Pot Synthesis of New-Phase AgInSe2Nanorods

AgInSe2 nanorods with a previously unknown orthorhombic phase isostructural to AgInS2 have been prepared by the thermolysis of [(PPh3)2AgIn(SeC{O}Ph)4] in a mixture of oleylamine (OA) and dodecanethiol (DT) at 185 degrees C. A systematic study indicates that the ratio of surfactants is crucial for obtaining both monodispersed nanorods and the new orthorhombic phase AgInSe2. The AgInSe2 nanorods have been characterized by TEM, XRPD, EDX, and XPS.

One-pot synthesis and third-order nonlinear optical properties of AgInS2 nanocrystals

Good quality colloidal nanocrystals of metastable orthorhombic phase of AgInS2 obtained by decomposing the single-precursor [(Ph3P)2AgIn(SCOPh)4] in a mixture of dodecanethiol and oleic acid at 125-200 degrees C, exhibit significant third order non-linear optical properties.