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Chalcopyrite CuAlS₂ nanoparticles were synthesized with polyol method. The solvothermal with autoclave nanoparticles synthesized are investigated. The amount and temperature of reducer, the solvent of salts could be important parameters that were studied. The nanoparticles were synthesized with CuCl, AlCl₃ and thiourea (SC(NH₂)₂) as precursors, diethylene glycol ((CH₂CH₂ OH)₂O) and polyethylene glycol 600 (HO(C₂H₄O)_nH) as solvent and capping agent respectively, and ammonia (NH₄OH) as reducing agent. The parameters of synthesis were studied by X-Ray diffraction (XRD) for analysis of structure, scanning electron microscope (SEM) for morphology and by ultraviolet–visible (UV–VIS) spectrophotometer for analysis of light structure. The possible formation mechanism is also discussed.

In this study, single-kesterite-phase Cu₂ZnSnS₄ (CZTS) and Cu₂ZnSnSe₄ (CZTSe) nanocrystallines have been synthesized by a simple solvothermal route. Scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible (UV-vis) absorbance and Raman scattering spectroscopy were used to characterize the optical and micro-structure properties of the as-synthesized samples. The bandgap of CZTS could be tuned in a large range by incorporating a few Se atoms. Both the CZTS and CZTSe exhibited the similar temperature dependence of the Raman "A" modes, including a monotonic redshift in peak position and an irregular variation in peak linewidth. Such a behavior might be due to the cumulative effect of thermal expansion and small crystalline sizes.

A ZnO nanoparticles (NPs)/reduced graphene oxide (rGO) composite was fabricated via a simple one-step solvothermal method with graphene oxide (GO) and Zn(NO₃)₂ ⋅ 6H₂O as the precursors. The morphology, crystal structure and optical properties of the synthesized materials were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy and photoluminescence (PL) spectroscopy. The synthesized composite exhibited rGO layers assorted with tiny ZnO NPs. rGO supposedly acted as a template in the solvothermal process, that may promote the preferential attachment of ZnO NPs and prevented the agglomeration of ZnO NPs in the synthesized composite. It was also found that the electrical properties of the composite improved markedly with bare ZnO NPs, without significantly changing the morphology and crystal structure of the ZnO NPs. The main aim of this research is to develop an efficient sensor and to understand the effect of graphene in sensing characteristics. The synthesized composite was exposed to H₂, CO and C₂H₂ gases to confirm its feasibility for gas sensing, and the results showed preferential detection of reducing gases at low temperature.

Bi₂S₃ nanocrystals with different shapes were synthesized via a simple solventothermal route. Nanorods and nanotubes can be obtained by changing reaction temperature. In the presence of surfactant, hollow nanospheres can be produced. The nanocrystals were characterized by X-ray powder diffraction and transmission electron microcopy. The growth mechanisms were discussed.

CdS nanoparticles with various size and shape were synthesized through solvothermal route using different ratios of ethylenediamine/water. X-ray diffraction and transmission electron microscopy results revealed that CdS nanorods were formed by using ethylenediamine and the mixture of ethylenediamine and water as solvents. The CdS nanorods had [002] preferential orientation. When water was used as the solvent, irregular shape particles and typical XRD patterns of hexagonal CdS were observed. The produced nanoparticles displayed interesting photoluminescence feature, which were found to be sensitive to the ratio of ethylenediamine/water. It is suggested that the different coordination ability with Cd²⁺ and dielectric constant of ethylenediamine and water caused different formation mechanism of CdS and led to the difference in the shape, crystallinity and optical properties of produced CdS particles.

Semiconductor quantum dots such as CdSe, PbSe, PbS, CdS, CuInS, CuInSe, etc. have been extensively studied for their size-tunable optical absorption and emission properties, which enable their applications in different optoelectronics applications. Although despite having high photoaborption and photosensing properties these semiconductor quantum dots possess certain limitation due to their high level of toxicity and complex synthesis process. Graphene quantum dots (GQDs) are a zero-dimensional (0D) nontoxic nanomaterial of the carbon family, and have sparked a lot of attention in the domains of optoelectronics and electronics. In this review, a number of GQD synthesis methods such as laser ablation, hydrothermal, solvothermal, thermal pyrolysis, electrochemical, chemical oxidation and cutting have been summarized in detail.

Zinc oxide (ZnO) is a compound with versatile applications. The compound can be synthesized in multiple sizes and shapes. The actual final product shape or morphology depends largely on the solvent used. The understanding of the actual interaction amongst the solvent and solute molecules is a very promising way to predict the shape of ZnO. Further, the operating conditions used during synthesis of ZnO also influence the final size of the product. This review paper specifically focuses on synthesis of zinc oxide through solvothermal synthesis with salt of zinc oxide with single solvent and with different operating conditions. The literature on effect of mixture of solvents is also reported in one of the subsections. The aim of this review is to understand the actual interaction amongst single salt and solvent without presence of any other compound in it. The presence of more than one compound in solvent or mixture of solvent increases the complexity of the problem. Therefore, there is a need to focus on this specific collection of literature to understand the basics, while future studies can be devoted to more complex studies. This review covers the effect of solvents like alcohols, alkanes, glycols, ring compounds and water on zinc salt. Also, it reports the effect of operating parameters like effect of precursor, temperature and time based on the available literature.

One-dimensional (1D) single crystalline CdS nanostructures have been successfully synthesized via a diphenylthiocarbazone-assisted solvothermal route. The results revealed that the microstructure and optical absorption properties of 1D CdS nanostructures were temperature and time dependent owing to thermodynamically and kinetically controlled growth. Single crystalline CdS nanowires with a diameter of 80 nm and length of 20 μm were synthesized at 180°C for 96 h. At moderate temperature (180°C), the morphology of the products transformed from irregular short rods to uniform long rods as the reaction time prolonging in a kinetically controlled growth regime. Only nanorods were obtained at a temperature as low as 120°C even extending reaction time to 260 h due to thermodynamic limited growth. At high temperature (250°C in this system), the products were nanowires with larger diameter but lower aspect ratio since the growth rates on both lateral and axial directions were accelerated. Moreover, the optical absorption spectra revealed that the CdS nanowires showed a blue shift compared with bulk CdS. Two optical absorption peaks appeared due to the nanometer effect in the radial and lengthwise directions of CdS nanowires. The growth mechanism of 1D CdS nanostructures was discussed.

In this paper, regularly shaped AlF₃ particles with cubic structure were successfully synthesized via a solvothermal route. The as-prepared products were characterized by X-ray powder diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results indicated that reaction temperature and time have significant effects on the morphology of the as-prepared products. A possible formation process has also been investigated on the basis of a series of XRD and SEM studies of the product obtained at different conditions. This well-controlled synthesis approach may be extended to fabricate other metal fluoride materials.

TiO₂@MWCNT heterostructure containing single one carbon nanotube has been successfully prepared via solvothermal method. X-ray diffration (XRD) analysis shows that TiO₂ nanocrystals only contain highly crystallized tetragonal anatase phase. Interestingly, scanning electron microscope (SEM) and transmission electron microscope (TEM) results show that most of the TiO₂ nanocrystals are perpendicular to the surface of multi-walled carbon nanotube (MWCNT) and only single one carbon nanotube is coated by TiO₂ crystals. The electromagnetic (EM) characteristics are investigated at 0.5–18.0 GHz range. The EM properties show that both the permittivity and the permeability present a typical resonance behavior at 11.0 GHz and 12.0 GHz, respectively. Besides, the TiO₂@MWCNT heterostructures exhibit a broadband absorption throughout the whole Ku wave bands (12.0–18.0 GHz). Interestingly, the reflection loss (RL) of the TiO₂@MWCNT heterostructures change slightly as the thickness of the heterostructures increase from 3.0 mm to 5.0 mm in the 8.0–13.0 GHz range.

In this work, reduced graphene oxide (RGO)/ferroferric oxide (RGO/Fe₃O₄) hybrid composite was successfully fabricated by a facile one-step solvothermal method. The structure, chemical composition, morphology and magnetic properties of the samples were investigated in detail. Fe₃O₄ microspheres with an average diameter of 250nm were uniformly anchored on the surface of the RGO sheets without large aggregation. Moreover, the results demonstrated that the hybrid composite exhibited obviously enhanced microwave absorption properties compared with the pure Fe₃O₄ microspheres. The minimum reflection loss (RL) of the hybrid composite reached $-$36.8dB at 17.2GHz with a thickness of 5.0mm and its effective absorption bandwidth (lower than $-$10dB) was 3.9GHz with a thickness of 2.5mm. Significantly, the hybrid composite exhibited a dual-waveband absorption characteristic covering the C and Ku bands. Besides, the relationship between the matching thickness and peak frequency was reasonably explained according to the quarter-wavelength matching theory. Therefore, the obtained composite was a promising candidate for application in microwave absorption.

In this work, we designed a simple substrate-immersed solvothermal route for the one-step synthesis of novel ordered SiO₂/Ag arrays, employing SiO₂ colloidal crystals as templates and alcohol as reducing agent. The Ag nanoparticles were uniformly deposited in situ onto SiO₂ colloidal crystals, which exhibited high surface enhanced Raman spectroscopy (SERS) activity and uniform SERS intensity. It was found that ordered SiO₂/Ag arrays could rapidly scavenge the absorbed-Nile blue A (NBA) molecules from the surfaces with the assistance of H₂O₂, while the SERS signals of NBA decreased sharply and almost completely disappeared within four minutes. This can be attributed to the superior catalytic activity of Ag nanoparticles. After five times of re-immersion and re-absorbing process of NBA, the substrates could still keep $\sim$ 74.8% SERS intensity versus the original. The high activity and durability of the as-prepared SiO₂/Ag SERS substrate endow them as a promising candidate for trace detection.

The olivine LiFePO₄ with various morphologies and different growth lattice planes was prepared by a controllable hydrothermal method with changing precursor concentration and using phytic acid as phosphorus source. The microstructure, crystal orientation and electrochemical performance of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and charge–discharge tests. The results show that the morphologies of all samples change from spindle-like to hierarchical plate-like and then to long plate-like shape, and the main exposed facets transform from (100) to (001). This indicates that the precursor concentration and phytic acid play important roles in exposing facets and controlling the morphology of LiFePO₄. In order to illustrate these phenomena, a reasonable assembly process is provided and the formation is explained. Li ion diffusion coefficient along [100] and [001] directions was calculated by using electrochemical impedance spectroscopy (EIS). The results show that the diffusion coefficient of (100) facet is higher than that of (001) facet, indicating a good electrochemical performance for (100) facet. In addition, the capacity test is carried out, which also confirms the above results. With the precursor concentration of 0.5M, the obtained LiFePO₄ with self-assembled hierarchical structure, smaller size and (100) facet shows the best electrochemical performance: 162.1mAh/g at 0.1C and 112.4mAh/g at 10C. Using phytic acid as phosphorus source and controlling precursor concentration to prepare high performance LiFePO₄ open up a new prospect for the production of cathode materials for lithium ion batteries.

We report a simple synthesis of C-doped ZnO composite nanoparticles by a solvothermal treatment of Zn(OAc)₂ ⋅ 2H₂O that provides a source of both zinc and carbon. The photocatalytic activities of the composites were evaluated by the degree of degradation rhodamine B in aqueous solutions at room temperature with near UV light irradiation. These nanocomposites exhibit higher photocatalytic activity compared with pure ZnO nanoparticles. The enhancement of photocatalytic activity of C-doped ZnO nanoparticles is mainly attributed to their absorbed more photons and reduced electron hole pair recombination.

TiO₂ nanorod (NR) arrays were prepared on FTO by the simple hydrothermal synthesizing method. On this basis, a layer of Bi₂S₃ quantum dots (QDs) was covered on the surface of TiO₂ NRs array by solvothermal method, by which the Nano Bi₂S₃/TiO₂ NRs composites films were obtained. The phase structure, morphologies, optical absorptions and photoelectrochemical (PEC) properties of the as-prepared materials were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Ultraviolet–visible spectroscopy (UV-Vis), Photoluminescence (PL) and electrochemical workstation. The results indicate that the concentration of tetrabutyl titanate (TBT) has a great influence on the morphology of the film, with the increase of TBT content, the array of TiO₂ NRs changed from loose to tight, and the thin films were cracked when the TBT volume is up to 0.7mL; The absorption of the TiO₂ NRs array film to the visible light is enhanced significantly when sensitized with Bi₂S₃ and the absorption wavelength is increased from 400nm to 800nm. Compared with the pure TiO₂, the fluorescence intensity of the TiO₂/Bi₂S₃ NRs is weakened, and there is no obvious fluorescence diffraction peak. Under the irradiation of standard (AM1.5G 100mW/cm${}^2)$, the photocurrent density of the composite film increased significantly. When the external bias voltage is 1.2V, the current density of the composite films is five times of that of the pure TiO₂.

Considering the high interests and concerns in regards to quantum dots (QDs), their properties and applications, this paper presents highly photoluminescent amino-functionalized carbon QDs which were prepared via a simple one-step method developed directly from pine needle. They were characterized by X-ray powder diffraction, photoluminescence (PL), UV-Vis diffused reflectance spectra, transmission electron microscope and scanning electron microscopy. These carbon QDs show strong and stable PL, which is dependent on excitation wavelength. The intense PL under longer excitation wavelength and excellent bioactivities suggest they can be used for biomedical applications due to its high photostability and biocompatibility.

For the synthesis of new materials and the growth of bulk crystals for specific applications, hydrothermal and solvothermal crystal growth provide a complementary alternative to conventional techniques. Crystals can usually be grown by these specialized techniques at temperatures well below their melting points, providing avenues for the growth of new phases or bulk crystals with a lower thermal strain. Metal–organic frameworks (MOFs)/coordination polymers (CPs), on account of their tunable structure, porosity and functionality, have been the subject of significant interest for a variety of applications. These materials with interesting structures are often synthesized using carboxylate organic linkers, which have proved to be quite stable under hydro/solvothermal conditions. Hence, in this chapter, we showcase examples of various carboxylate ligand-containing MOFs/CPs fabricated using transition metal ions [e.g., Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)], lanthanide metal ions [e.g., La(III), Ce(III) and Sm(III)] and tetravalent Zr(IV) metal ions by using hydro/solvothermal reaction conditions. Additionally, in order to better understand the significance of some of the key factors affecting MOFs/CPs construction during the hydro/solvothermal reaction conditions, we also discuss some of the factors, such as solvent, temperature, pH and molar ratio of the reactants, affecting their hydro/solvothermal syntheses.