Papers by Keyword: Hydrothermal

Abstract: ZnO nanostructures were synthesized by hydrothermal method at different temperatures and growth times. The effect of increasing the temperature on structural and optical properties of ZnO were analyzed and discussed. The prepared ZnO nanostructures were characterized by X-ray diffraction (XRD), UV–Vis. absorption spectroscopy (UV–Vis.), Photoluminescence (PL), and scanning electron microscopy (SEM). In this work, hexagonal crystal structure prepared ZnO nanostructures was observed using X-ray diffraction (XRD) and the average crystallite size equal 14.7 and 23.8 nm for samples synthesized at growth time 7 and 8 hours respectively. A nanotubes-shaped surface morphology was found using scanning electron microscopy (SEM). The optical properties showed that the samples had good absorbance in the UV-Vis. region and wide band gap. The PL spectrum displayed that the intensity of ultraviolet (UV), band gap and defect bands depend on the growth temperature of the ZnO nanostructure. The largest band gap was 3.351 eV for ZnO nanostructure synthesized at 100 °C and growth time 8h.

Abstract: Mordenite is well-known as a commercial catalyst in oil refineries. Conventionally, mordenite is produced through hydrothermal method under static condition for long period of time. In this investigation, the effect of intermittent agitating of the solution during the hydrothermal process on the mordenite properties and ammonium sorption was studied. The synthesized mordenite samples were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The XRD pattern of the intermittent agitated sample showed broader peaks with similar intensity peaks as compared to the non-intermittent agitated sample. According to the SEM images, the average particle size of the intermittent agitated sample was 1.8 μm, while the non-intermittent agitated sample was larger with 13 μm. Both of samples show similar morphology as ellipsoid like. The sample of mordenite from the intermittent agitated sample showed a lower bulk density and high particle dispersion in water. The ammonium adsorption on the mordenite samples were tested by using various volume of ammonium solution. The ammonium adsorption capacity of the intermittent agitated sample slightly higher than the non-intermittent agitated mordenite. This simple intermittent agitated action which favored smaller particle size of mordenite could be beneficially applied for other applications dealing with bulky molecules due to the lower mass transfer limitation.

Abstract: Photo-supercapacitor (PSC) is integrated harvesting energy, that a combination of DSSC with a symmetric supercapacitor. A crucial part of the conversion of photon energy by DSSC is a photoanode. The DSSC photoanode used ZnO NR, because it is known as one of the optical semiconductor materials, which has bandgap of 3.37 eV. Due to good cycle stability and high conductivity, the supercapacitor electrode uses activated carbon-carbon black (AC-CB) materials. This study observed the enhance of temperature growth on the structure, morphology, and optical properties of ZnO NR photoanode to improve the photo-supercapacitor's performance. The hydrothermal method has been chosen to grow ZnO NR photoanode at growth temperature of 100, 150, and 200 °C for 4 hours. The structure, morphology, and optical properties of ZnO NR were analyzed by XRD, SEM-EDX, and UV Vis, respectively. The electrical performance of photo-supercapacitor were analyzed by IV data. XRD pattern has identified an increase peak in the hkl (002) of c-axis orientation and SEM data has identified that ZnO NR grows perpendicular to the substrate according to the preferred orientation. The optical properties has identified a shift to a small bandgap (redshift). For the electrical performance, photo-supercapacitor has increased in maximum current (I_max) as the growth temperature increases, and the maximum current is obtained by a growth temperature of 200 °C, which is 14.45 μA.

Abstract: Recently, molybdenum disulfide (MoS₂), have been explored as photothermal materials for solar evaporation. However, the optimum phase for photothermal material, 1T-MoS₂ or 2H-MoS_2, is still debatable. In this work, we observed the morphological and structural properties of MoS₂ prepared by a simple hydrothermal process at 200 °C in three different growth times (16, 20, and 24 hours) using Na₂MoO₄·2H₂O (sodium molybdate) as a Mo precursor, and CS(NH₂)₂ (thiourea) as S precursor. MoS₂ nanoflowers were successfully prepared with nanosheets petals and its diameter increased from 0.4 to 2.8 and 4.5 as the growth time increased from 16 to 20 and 24 hours. The increase in growth time also led to improve the Mo:S ratio from 1:8 to 1:5 and facilitate the phase transformation from 1T to 2H as indicated by the shifting of (002) diffraction peak from 9.25° to higher degrees (12.98°, and 14.12°).

Abstract: Molybdenum disulfide (MoS₂) is one of the promising 2D materials thanks to its outstanding physicochemical properties and therefore is predicted to play a key role in optoelectronics devices and energy applications. MoS₂ exhibits three phases with distinctive crystal structure depending on its stacking order: 1T (metallic), 2H (semiconducting), and 3R (semiconducting). Among all of them, 1T-MoS₂ has become the center of interest due to its e.g., high catalytic activity. However, most of the methods to obtain 1T-MoS₂ are complex and costly, for example strain engineering, electron beam treatment, and plasmonic hot electron injection. As response, we here demonstrate a facile and cost-efficient hydrothermal route at 200 °C to synthesize MoS₂ with high content of 1T phase. MoS₂-200 °C nanoflowers has an average diameter of 2.96 µm with the S/Mo atomic ratio of 1.50 and the band gap of 1.39 eV. It has an additional diffraction peak at 2θ = 9.22^o_, indicating the transformation of semiconducting 2H into metallic 1T. Higher concentration of 1T phase in MoS₂-200 °C is also indicated by high intensity of the E_1g Raman peak.

Abstract: There is a need to address the gap between the theoretical benefits and cost-efficient production of supercapacitors in the market in order to sway the preference of the industry from the current perishable energy sources and storage. More extensive exploration of sustainable fabrication methods and materials used for renewable energy storage are just some of the factors that would decrease this gap. A binder-free supercapacitor electrode made of NiCo₂O₄ and carbonized kapok fiber paper (CKFP) was successfully fabricated by hydrothermal process at relatively low temperatures. NiCo₂O₄ urchin-like structures were deposited on the surface of carbon fiber paper (CFP) and CKFP. XRD analysis confirmed the successful conversion of kapok fiber paper to CKFP after pyrolysis, as well as the growth of pure spinel NiCo₂O₄ nanostructures on CFP and CKFP. The cyclic voltammetry curves showed that the CFP-NiCo₂O₄ prepared at 140 °C had the highest specific capacitance of 143.51 Fg^-1 at 2 mVs^-1. The CKFP-NiCo₂O₄ synthesized at the same temperature yielded slightly higher specific capacitance of 146.29 Fg^-1 at 2 mVs^-1, and 508 Fg^-1 at 0.5 Ag^-1.

Abstract: The aim of this study is to investigate the photoluminescence (PL) properties of europium (Eu) doped alumina as potential platform for simultaneous bio Imaging and drug delivery. Synthesis of Eu doped alumina is done by a facile two step method. In the first stage, hydrothermal synthesis is used to prepare the Eu doped ammonium aluminum carbonate hydroxide which is then calcined to get a crystalline Eu doped alumina. Structural characterization of the prepared sample is done through XRD and SEM. Photoluminescence spectroscopy is performed in order the study the PL response. The SEM images of the Eu doped sample revealed whisker shaped morphology, the porosity in the inter and intra whisker region is beneficial for the high drug loading capacity. The length of the bundle after annealing was about 5 µm with the bundle diameter of 0.45 µm. XRD patterns of the prepared sample has sharp peaks, showing a high degree of crystallinity corresponding to the α-alumina phase. Finally PL response was checked at an excitation wavelength of 393 nm. A dominant peak was observed at a wavelength of 613 nm corresponding to the 5D0 to 7F2 transition.The3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay confirms the cell viability of more than 100% at even a concentration of 500 nano molar alumina in phosphate-buffered saline (PBS). These results show that the Eu doped alumina having optimum PL response, high biocompatibility and drug loading capacity which makes it a promising candidate for theranostic applications.

Abstract: Hydroxyapatite (HA) is a calcium phosphate compound [Ca₁₀(PO₄)₆(OH)₂] which is non-toxic and has high biocompatibility. HA can be synthesized from natural basic ingredients with high calcium carbonate (CaCO₃) content such as chicken eggshells. Here, we reported the synthesis of HA from chicken eggshells by hydrothermal methods. The effects of temperature synthesis of 120 °C and 230 °C on the purity and crystallinity were investigated in order to get information about best synthesis temperature for producing high quality of HA. The structure and crystallinity of HA were determined by XRD and FTIR. Morphology of HA is determined by TEM, while the composition was determined by XRF, respectively. High purity samples of HA with hexagonal structure of P63/m were successfully obtained with synthesis temperature of 120 °C and 230 °C. For HA synthesized in 120°C, the purity was 97.7%, while for HA synthesized in 230 °C, the purity was 97.8%. Two types of impurities, namely Ca(OH)₂ and tricalcium phosphate (TCP) ware detected in both samples, It was also obtained the degree of crystallinity of 26.86% and 56.46% for samples synthesized at 120 °C and 230 °C, respectively. HA synthesized with at 230 °C has a higher and better crystallinity.

Abstract: Magnetite nanoparticles have been successfully prepared by hydrothermal method from FeCl₃ as starting material. The properties and morphology of the products with different synthesis time and FeCl₃ concentration were investigated. Firstly, the FeCl₃ with concentration of 0.05 – 0.15 M and 0.10 M sodium citrate as well as 0.15 M were mixed with distilled water containing 0.1 g polyethylene glycol. Subsequenly, the solution was transferred into a Teflon-lined autoclave and it heated into an oven at 210°C for 12 hours. The black precipitate that formed was separated by a bar magnet, then washed with water and ethanol, and dried at 60°C overnight. The magnetite formation begun at 3.5 hours synthesis time with crystal diameter in range of 9.4-30 nm. The crystallinity and crystal size of magnetite increased with reaction time and concentration of FeCl₃. The magnetite nanoparticles had a mesoporous structure and bigger pores at higher concentration. The saturation magnetization (Ms) of magnetite was in the range of 59 – 81 Emu/g with coercivity value was near to zero showing that magnetite nanoparticle had superparamagnetic properties.

Abstract: In this study ZnO photocatalysts with different loading of Eu₂O₃ and Sm₂O₃ were prepared vie microwave-assisted hydrothermal method. The prepared samples were investigated by using XRD, SEM and BET analysis. The photocatalytic activity was determined by degradation of methylene blue (MB) under Osram Vitalux illumination. Prepared ZnO photocatalysts shown high photocatalytic activity under solar light simulated radiation. After 30 minute of irradiation more than 95 % of initial MB solution was degraded. The effect of pH and photocatalyst dosage was investigated. The reusability of photocatalysts was also studied.