Microwave Hydrothermal Process Research Articles

Fundamental properties and phosphorus transformation mechanism of soybean straw during microwave hydrothermal conversion process

Microwave hydrothermal (MHT) conversion is emerging as a promising technology for the disposal and reutilization of biowastes. This study investigated the fundamental properties and phosphorus transformation mechanism of soybean straw during the MHT conversion process. The oxygen-containing functional groups in soybean straw were stripped, and a trend of dehydration was observed as the temperature increased during the MHT process. Cellulose was identified as the major component of the MHT solid products at high temperature. Glucose and glucuronic acid in the MHT liquid products were gradually converted to formic acid and acetic acid with increasing temperature and holding time. The characteristics of the MHT products directly affected the changes in P speciation and transformation. Most of the P was distributed in liquid products and the impact of holding time was not significant on P distribution at low MHT temperature. With the increase in temperature and holding time, P gradually transferred into the solid products. The proportion of organic phosphorus and soluble inorganic phosphorus in soybean straw was high, and it decreased noticeably after the MHT process. The increase in MHT temperature promoted the conversion of OP and AP into IP and NAIP respectively. P K-edge X-ray absorption near edge structure analysis reveals that Ca5(PO4)3(OH) was the major component of soybean straw and more Ca5(PO4)3(OH) was formed at lower MHT temperature. This study provides fundamental knowledge on the property changes of soybean straw and the transformation of phosphorus during MHT conversion process, which is essential for its disposal and further utilization.

Enhanced management and antifouling performance of a novel NiFe-LDH@MnO2/PVDF hybrid membrane for efficient oily wastewater treatment

Layered double hydroxides (LDHs) have gained significant recognition for their facile synthesis and super-hydrophilic two-dimensional (2D) structure to fabricate antifouling membranes for oily wastewater separation. However, conventional PVDF membranes, due to their hydrophobic nature and inert matrix, often exhibit insufficient permeance and compatibility. In this study, a novel NiFe-LDH@MnO2/PVDF membrane was synthesized using ultrasonic, redox, and microwave-hydrothermal processes. This innovative approach cultivated grass-like NiFe-LDH@MnO2 nanoparticles within an inert PVDF matrix, promoting the growth of highly hydrophilic composites. The presence of NiFe-LDH@MnO2 resulted in pronounced enhancements in surface morphology, interfacial wettability, and oil rejection for the fabricated membrane. The optimal NiFe-LDH@MnO2/PVDF-2 membrane exhibited an extremely high pure water flux (1364 L m−2•h−1), and increased oil rejection (from 81.2% to 93.5%) without sacrificing water permeation compared to the original PVDF membrane. Additionally, the NiFe-LDH@MnO2/PVDF membrane demonstrated remarkable antifouling properties, evident by an exceptional fouling resistance ratio of 96.8% following slight water rinsing. Mechanistic insights into the enhanced antifouling performance were elucidated through a comparative “semi-immersion” investigation. The facile synthesis method, coupled with the improved membrane performance, highlights the potential application prospects of this hybrid membrane in emulsified oily wastewater treatment and environmental remediation.

Enhancement of upconversion luminescence in Yb3+/Er3+-doped BiVO4 through calcination

Dopant concentration is generally increased in order to enhance the emission efficiency of the upconversion phosphor materials. However, a higher doping concentration generally results in concentration quenching of the upconversion emission resulting in low upconversion efficiency. In such instances, the calcination technique can offer an alternate way of enhancing the emission efficiency of the upconversion phosphors. Here, Yb3+/Er3+-doped BiVO4 has been synthesized by microwave hydrothermal process and the as-synthesized phosphor was calcined at 900 °C in air. Yb3+/Er3+-doped BiVO4 phosphor has been systematically characterized. The elemental distribution is homogeneous. Phase change has occurred from the tetragonal BiVO4 of the as-synthesized sample to the mixture of tetragonal and monoclinic BiVO4 in the calcined sample. The bandgap of the calcined sample has been reduced by 0.52 eV as compared to the as-synthesized one. Under 980 nm excitation, the calcined sample shows ∼ 7 and 15-fold enhancement in the upconversion and downshifting emission intensity, respectively, as compared to the as-synthesized sample. The calcination is found to have increased the lifetime of all the emitting excited states resulting in enhanced emission efficiency which has been confirmed by the time-resolved photoluminescence measurements.

Enhanced Structural and Electrochemical Properties of Zn-Doped NiCo2O4 Synthesized by Low-Temperature Microwave Hydrothermal Process

The specific capacitance (Cp) is an important parameter influencing the energy storage capacity of materials. In this study, a series of NiZn x Co2-x O4 (x = 0.0–0.10) nanoparticles were prepared using the microwave-hydrothermal (M-H) method. The samples were characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform Infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and electrochemical studies. It is observed from X-ray diffraction that all the samples are cubic in nature with space group Fd-3m. The average lattice constant is varied in between 7.63 (x = 0.0) to 8.34 (x = 0.10). The linear increase in lattice constant is due to the difference in the ionic radii. The average grain size is in the range of 80 (x = 0.0) − 124 nm (x = 0.10) for all the samples, and grains are found to be spherical in nature. The characteristic metal oxygen vibration bands were observed at 578 cm−1 and 661 cm−1. The valence states of Ni2+/Ni3+, Co2+/Co3+ and Zn2+ were confirmed by X-ray photoelectron spectroscopy. The electrochemical studies were performed on all the samples. The high value of specific capacitance (Cp) 871.91 Fg−1 is observed for sample x = 0.06. Therefore, Zn doped NiCo2O4 shows good impedance and electrochemical properties which is promising material for supercapacitor applications.

Production of Hydrogels from Microwave-Assisted Hydrothermal Fractionation of Blackcurrant Pomace.

The exploitation of unavoidable food supply chain wastes resulting from primary and secondary processing for chemicals, materials, and bioenergy is an important concept in the drive towards circular-based, resource-efficient biorefineries rather than petroleum refineries. The potential production of hydrogels (materials) from unavoidable food supply chain wastes, which are naturally rich in biopolymers such as cellulose, hemicellulose, pectin, and lignin, represents an interesting opportunity. However, these intertwined and interconnected biopolymers require separation and deconstruction prior to any useful application. Thus, this study aims to explore the formation of hydrogels from defibrillated celluloses (MW-DFCs) produced via acid-free stepwise microwave hydrothermal processing of blackcurrant pomace residues. Initially, pectin was removed from blackcurrant pomace residues (MW, 100-160 °C), and the resultant depectinated residues were reprocessed at 160 °C. The pectin yield increased from 2.36 wt.% (MW, 100 °C) to 3.07 wt.% (MW, 140 °C) and then decreased to 2.05 wt.% (MW, 160 °C). The isolated pectins were characterized by attenuated total reflectance infrared spectroscopy (ATR-IR), thermogravimetric analysis (TGA), and 13C NMR (D2O). The cellulosic-rich residues were reprocessed (MW, 160 °C) and further characterized by ATR-IR, TGA, and Klason lignin analysis. All the MW-DFCs contained significant lignin content, which prevented hydrogel formation. However, subsequent bleaching (H2O2/OH-) afforded off-white samples with improved gelling ability at the concentration of 5% w/v. Confocal laser microscopy (CLSM) revealed the removal of lignin and a more pronounced cellulosic-rich material. In conclusion, the microwave-assisted defibrillation of blackcurrant pomace, an exploitable unavoidable food supply chain waste, affords cellulosic-rich materials with the propensity to form hydrogels which may serve useful applications when put back into food products, pharmaceuticals, cosmetics, and home and personal care products.

Multifunctional carboxylated cellulose nanofibers/exfoliated bentonite/Ti3C2 aerogel for efficient oil adsorption and recovery: The dual effect of exfoliated bentonite and MXene

Discharge of oily wastewater with poor fluidity could cause serious environmental pollution. Therefore, rapid and efficient removal and recovery of oil is still a global problem. Currently, two-dimensional (2D) Ti3C2 MXene materials with high photothermal performance have attracted extensive attention in photothermal-assisted crude oil wastewater treatment. However, the poor stability of Ti3C2 severely limits the application in the development of photothermal aerogels. In this study, porous CNF-C/BTex/Ti3C2 aerogel was constructed by synergistically introducing cost-effective exfoliated bentonite (BTex) and Ti3C2 MXene combined with carboxylated cellulose nanofibers (CNF-C) through a simple in situ co-precipitation coupling with microwave hydrothermal and solution impregnation processes. The introduced BTex efficiently restrained the oxidation of Ti3C2 during the preparation process, and synergistically enhanced the structural stability, mechanical and adsorption properties of aerogel. Specifically, CNF-C/BTex/Ti3C2 exhibited excellent stability (structural, thermal and chemical stability), thermal resistance, hydrophobic properties (water contact angle was 149°), and mechanical properties (full recovery at 60% strain), which was conducive to adsorption of common oils (up to 46–90 times than its original weight). In addition, CNF-C/BTex/Ti3C2 has outstanding photothermal conversion efficiency (light absorption efficiency was 99% and the surface temperature reached up to 75.2 °C under 1-sun irradiation:1 kW·m−2) and thermal conductivity (104 mW/m·K), which allows CNF-C/BTex/Ti3C2 to adsorb more than 48 times than its original weight of crude oil (adsorption capacity up to 48 g·g−1) under 1-sun irradiation (1 kW·m−2) within 25 s. Furthermore, enhanced adsorption mechanisms for common oils and high-viscosity crude oil have been proposed. The study provides a new option for the development of efficient and stable cellulose-based adsorbents for oily wastewater remediation by introducing low-cost bentonite and MXene.

Microwave hydrothermal preparation of reduced graphene oxide-induced p-AgO/n-MoO3 heterostructures for enhanced photocatalytic activity through S-scheme mechanism and its electronic performance.

Through a powerful and modest closed system Microwave hydrothermal process, a methodological analysis is made in the rational synthesis of the reduced graphene oxide-induced p-AgO/n-MoO3 (RGAM) heterostructures. These have strong p-n junction heterostructures with considerable electron-hole recombination functioning as solar catalysts. The enhanced photocatalytic activity through the plasmonic step scheme (S-scheme mechanism) describes the effective charge recombination process. The energy band positions, bandgap, and work function are determined to understand the Fermi level shifts; this describes the S-scheme mechanism by UPS analysis which assessed an electron transfer between AgO and MoO3, yielding work function values of 6.34 eV and 6.62eV, respectively. This photocatalytic activity aids in dye removal by 94.22%, and heavy metals such as chromium (Cr) are eliminated by the surface action of sunlight on the produced material during solar irradiation. Electrochemical studies such as photocurrent response, cyclic voltammogram, and electrochemical impedance spectroscopy for RGAM heterostructures were also carried out. The study helps to broaden the search for and development of new hybrid carbon composites for electrochemical applications.

Microstructure and thermoelectric properties of nanoparticled copper selenide alloys synthesized using a microwave-assisted hydrothermal method

With the fabrication of high-performance thermoelectric (TE) materials, developments are being made in enhancing the figure of merit, zT , of TE materials. Liquid-like binary copper selenide (Cu 2 Se) chalcogenides recently gained significant recognition because of their anomalous but fascinating electrical and thermal transport performances. In this study, a facile synthesis technique was adopted in fabricating Cu 2 Se nanoparticles using a rapid microwave-assisted hydrothermal route at different reaction times. The results were compared with those of the Cu 2 Se solid-state (SS) sample synthesized using the traditional melting and annealing technique. X-ray diffraction patterns revealed successful synthesis of nanoparticles and a phase transition from orthorhombic α -phase and cubic β -phase to a single orthorhombic structure after hot-pressing. Scanning electron microscopic images revealed that although the grain sizes of the nanoparticle (NP) bulk samples increased with the reaction time of the microwave hydrothermal process, the grain sizes were significantly smaller than that of the SS sample. Additionally, NP bulk samples exhibited plenty of nano-grains and pores that are absent in the SS sample. The size and distribution of the grains and pores were measured to study their effects on the transport of carriers and phonons. The NP30 sample exhibited the highest power factor of 983.3 μW K − 2 m at 673 K among the NP samples, exhibiting intermediate values of resistivity and Seebeck coefficient that are close to those of the SS sample. Moreover, the NP samples exhibited appreciably lower thermal conductivity than the SS sample that is attributed to strengthened phonon scattering. The minimum thermal conductivity of the NP05 sample, 0.78 WK −1 m − 1 at 348 K, is 1.7 times lower than that of the SS sample. Finally, a maximum zT of 0.56 at 673 K, being approximately 1.3 times higher than that of the SS sample owing to the optimized thermal conductivity, was achieved for the NP30 sample. This value is comparable to or higher than that reported for Cu 2 Se synthesized using the traditional SS method. Investigations revealed that the proposed microwave hydrothermal synthesis technique is a facile, rapid, and reliable method that results in Cu 2 Se alloys with excellent TE performance.

Photocatalytic Degradation of Methylene Blue and Anticancer Response of In2O3/RGO Nanocomposites Prepared by a Microwave-Assisted Hydrothermal Synthesis Process.

The incorporation of graphene with metal oxide has been widely explored in various fields, including energy storage devices, optical applications, biomedical applications, and water remediation. This research aimed to assess the impact of reduced graphene oxide (RGO) doping on the photocatalytic and anticancer properties of In2O3 nanoparticles. Pure and In2O3/RGO nanocomposites were effectively synthesized using the single-step microwave hydrothermal process. XRD, TEM, SEM, EDX, XPS, Raman, UV-Vis, and PL spectroscopy were carefully utilized to characterize the prepared samples. XRD data showed that synthesized In2O3 nanoparticles had high crystallinity with a decreased crystal size after RGO doping. TEM and SEM images revealed that the In2O3 NPs were spherical and uniformly embedded onto the surface of RGO sheets. Elemental analysis of In2O3/RGO NC confirmed the presence of In, O, and C without impurities. Raman analysis indicated the successful fabrication of In2O3 onto the RGO surface. Uv-Vis analysis showed that the band gap energy was changed with RGO addition. Raman spectra confirmed that In2O3 nanoparticles were successfully anchored onto the RGO sheet. PL results indicated that the prepared In2O3/RGO NCs can be applied to enhance photocatalytic activity and biomedical applications. In the degradation experiment, In2O3/RGO NCs exhibited superior photocatalytic activity compared to that of pure In2O3. The degradation efficiency of In2O3/RGO NCs for MB dye was up to 90%. Biological data revealed that the cytotoxicity effect of In2O3/RGO NCs was higher than In2O3 NPs in human colorectal (HCT116) and liver (HepG2) cancer cells. Importantly, the In2O3/RGO NCs exhibited better biocompatibility against human normal peripheral blood mononuclear cells (PBMCs). All the results suggest that RGO addition improves the photocatalytic and anticancer activity of In2O3 NPs. This study highlights the potential of In2O3/RGO NCs as an efficient photocatalyst and therapeutic material for water remediation and biomedicine.

Visible light-driven photocatalytic bacterial inactivation on PPE, supported by the DFT and bactericidal study.

A novel ZnO-MoO3-ZnMoO3@graphene GZM composite catalyst prepared by microwave hydrothermal process for personal protective equipment textiles (PPE) is presented in this study. The results indicated that the GZM with defect vacancy sites of two types as observed by EPR showed significantly superior inactivation of the E. coli bacteria compared to GZM without the lower defect vacancy sites and concomitant lower electron densities. Photocatalytic activated oxidation by the GZM composites coatings was observed to proceed in acceptable times as well as the bacterial inactivation (log bact. C/Co > 107 within 3h). Defect sites in the GZM seem to be important leading to the bacterial inactivation process. DFT calculations on the GZM with and without catalyst defect sites were carried out. The electron densities were estimated by the Fourier mapping. The results found in this study showed the potential of GZM-PPE for practical applications.

Electrochemical Properties of Fe Doped NiCo2O4 Synthesised by Low-Temperature Microwave Hydrothermal Process

Electrochemical Properties of Fe Doped NiCo2O4 Synthesised by Low-Temperature Microwave Hydrothermal Process

A Facile Microwave Hydrothermal Synthesis of ZnFe2O4/rGO Nanocomposites for Supercapacitor Electrodes

As a typical binary transition metal oxide, ZnFe2O4 has attracted considerable attention for supercapacitor electrodes due to its high theoretical specific capacitance. However, the reported synthesis processes of ZnFe2O4 are complicated and ZnFe2O4 nanoparticles are easily agglomerated, leading to poor cycle life and unfavorable capacity. Herein, a facile microwave hydrothermal process was used to prepare ZnFe2O4/reduced graphene oxide (rGO) nanocomposites in this work. The influence of rGO content on the morphology, structure, and electrochemical performance of ZnFe2O4/rGO nanocomposites was systematically investigated. Due to the uniform distribution of ZnFe2O4 nanoparticles on the rGO surface and the high specific surface area and rich pore structures, the as-prepared ZnFe2O4/rGO electrode with 44.3 wt.% rGO content exhibits a high specific capacitance of 628 F g-1 and long cycle life of 89% retention over 2500 cycles at 1 A g-1. This work provides a new process for synthesizing binary transition metal oxide and developing a new strategy for realizing high-performance composites for supercapacitor electrodes.

Role of reaction adsorption on the production of 5-hydroxymethylfurfural from fructose under microwave hydrothermal process

5-Hydroxymethylfurfural (HMF) has been considered a valuable biomass-derived platform chemical that can be produced by hexose dehydration in the presence of an acid. However, the yield of HMF is always reduced because of side reactions such as rehydration and condensation. In this work, the reactive adsorption process of fructose dehydration to HMF catalyzed by hydrochloric acid under microwave condition was studied. BP2000 has better adsorption capacity than activated carbon (AC) in reactive adsorption, and addition of BP2000 increases the HMF yield. The maximum theoretical yield of HMF was 65 % obtained by adding 39 g L−1 BP2000 and reacting for 4 min at 160 °C under a microwave hydrothermal condition. It was discovered thatmicrowave hydrothermal technology (MHT) could significantly increase efficiency and reduce reaction time. Reactive adsorption could efficiently buffer HMF from side reactions when reaction conditions became severe, thereby increasing the HMF yield. Reactive adsorption provides a more sustainable method for HMF production and separation.

Synthesis and characterization of red-emitting Yb/Ho-CaSiO3 upconversion phosphors

Host material plays an important role in obtaining efficient photon upconversion and downshifting luminescence. Generally, fluoride and oxyfluoride glasses-based materials are used for high-efficiency photon upconversion. However, the poor thermal stability of fluoride glasses and the toxicity of fluorine ions limit their applications. In this report, Yb/Ho-doped CaSiO3 wollastonite phosphors have been demonstrated as efficient red-emitting upconversion phosphors. The phosphors have been synthesized by microwave hydrothermal process followed by heat treatment at 1050 ​°C in the air environment. 2M phase of the β-wollastonite has been confirmed by X-ray diffraction and Raman spectroscopy while the existence of the Yb and Ho dopants in the CaSiO3 lattice has been confirmed by X-ray photoelectron spectroscopy. The synthesized samples showed strong red upconversion emission centered at 662 ​nm and near-infrared downshifting emissions at 2016 ​nm upon 980 ​nm excitation. The emissions were found to depend significantly on the Ho concentration. Temporal evolution of the main emission bands was investigated to show that the energy transfer upconversion from Yb to Ho ions was responsible for the efficient upconversion and downshifting phenomenon.

Production of value-added hydrochar from single-mode microwave hydrothermal carbonization of oil palm waste for de-chlorination of domestic water

A huge amount of palm waste generated daily represents a problematic high-moisture waste to be disposed of, yet it also represents a promising biomass resource to be transformed into a value-added product. A single-mode microwave hydrothermal carbonization process incorporating steam purging was developed and utilised to convert high-moisture palm waste into hydrochar over a range of process temperatures from 150 to 300 °C. The microwave hydrothermal carbonization recorded a shorter process duration (10 min) and prevented the occurrence of hot spots within the reactor. The resulting hydrochar showed up to 94.3 wt% of mass yield, 69.2 wt% of fixed carbon, and 412.3 m2/g of surface area. The subsequent application of the hydrochar in de-chlorination of domestic water demonstrated an impressive removal performance of up to 98.9% of free chlorine, exhibiting 435 min of breakthrough time, and 40.0 mg/g of bed capacity in continuous column operation. The results show great promise of microwave hydrothermal carbonization as a desirable approach to produce desirable hydrochar for de-chlorination application.

Microwave hydrothermal renovating and reassembling spent lithium cobalt oxide for lithium-ion battery

With the growing number of lithium-ion batteries (LIBs) that are consumed by worldwide people, recycling is necessary for addressing environmental problems and alleviating energy crisis. Especially, it is meaningful to regenerate LIBs from spent batteries. In this paper, the microwave hydrothermal method is used to replenish lithium, assemble particles and optimize the crystal structure of the spent lithium cobalt oxide. The microwave hydrothermal process can shorten the reaction time, improve the internal structure, and uniformize the particle size distribution of lithium cobalt oxide. It helps to construct a regenerated lithium cobalt oxide (LiCoO2) battery with high-capacity and high-rate properties (141.7 mAh g−1 at 5C). The cycle retention rate is 94.5% after 100 cycles, which is far exceeding the original lithium cobalt oxide (89.7%) and LiCoO2 regenerated by normal hydrothermal method (88.3%). This work demonstrates the feasibility to get lithium cobalt oxide batteries with good structural stability from spent lithium cobalt oxide batteries.

Effective microwave-hydrothermal reduction of graphene oxide for efficient energy storage

Reduced graphene oxide (rGO) is an important member of the family of graphene-based nanomaterials. Conventional strategies for preparing rGO include chemical, thermal, photo, laser, hydrothermal, and microwave reduction. Here we report on a rapid microwave-hydrothermal (MH) method for the effective production of pure rGO (denoted as M-rGO) without using any reducing agents. The MH process was optimized in terms of temperature and duration to tune the structure and composition of the formed M-rGO to attain high specific capacitance for energy storage. The M-rGO possessed a three-dimensional (3D) interconnected porous structure with the C/O ratio of 9:5. The 3D interconnected structure of M-rGO not only increased the active surface area and enhanced the electrical double layer capacitance, but also improved its stability. Retaining the appropriate proportion of active functional groups also made a notable contribution of pseudocapacitance. The synthesized M-rGO exhibited a much higher capacitance of 298 F g−1 (1 A g−1, 0.5 M H2SO4) for a three-electrode system and 263 F g−1 (0.5 A g−1, 20% H2SO4- PVA gel) for a two-electrode system, as well as much better capacitance retention and cyclability, in contrast to conventional chemically reduced graphene oxide (C-rGO) and thermally reduced graphene oxide (T-rGO). Moreover, the energy density of the M-rGO was very high (36.6 Wh kg−1) at a power density of 0.5 kW kg−1. This first-rate energy storage performance of the M-rGO can be attributed to its highly active surface area, appropriate carbon-oxygen ratio, porous structure, and interconnected 3D morphology.

Speciation evolution and transformation mechanism of P during microwave hydrothermal process of sewage sludge

Due to the global shortage of phosphate ore, sewage sludge is an important resource for P recovery. This study aims to investigate how P was migrated and transformed during the microwave hydrothermal (MHT) process of sewage sludge. The effects of MHT and hydrothermal (HT) conversion were compared. The results reveals that there were no significant differences on the P distribution and speciation changes between the HT and MHT products, especially under high hydrothermal temperature. Ortho-P/Pyro-P was the dominant P form in the hydrothermal solid products, and high temperature promoted the transformation of C-O-P to Ortho-P/Pyro-P. The analysis of X-ray absorption near edge structure (XANES) shows that Ca5(PO4)3OH was formed after the hydrothermal processes. The relative abundance of Ca-P decreased first and then increased with increasing hydrothermal temperature. Moderate MHT temperature (170 °C) and holding time (30–60 min) promoted the transformation of P to the liquid products. Generally, the effect of MHT temperature was more significant than that of heating type and holding time on the variations of P distribution and speciations.

Synthesis of SAPO-34 Nanoplates with High Si/Al Ratio and Improved Acid Site Density.

Two-dimensional SAPO-34 molecular sieves were synthesized by microwave hydrothermal process. The concentrations of structure directing agent (SDA), phosphoric acid, and silicon in the gel solution were varied and their effect on phase, shape, and composition of synthesized particles was studied. The synthesized particles were characterized by various techniques using SEM, XRD, BET, EDX, and NH3-TPD. Various morphologies of particles including isotropic, hyper rectangle, and nanoplates were obtained. It was found that the Si/Al ratio of the SAPO-34 particles was in a direct relationship with the density of acid sites. Moreover, the gel composition and preparation affected the chemistry of the synthesized particles. The slow addition of phosphoric acid improved the homogeneity of synthesis gel and resulted in SAPO-34 nanoplates with high density of acid sites, 3.482 mmol/g. The SAPO-34 nanoplates are expected to serve as a high performance catalyst due to the low mass transfer resistance and the high density of active sites.

Controllable Synthesis and Luminescence Properties of Zn2GeO4 : Mn2+ Nanorod Phosphors

AbstractIn this study, color tunable phosphors (Mn2+‐doped Zn2GeO4) were successfully synthesized by a facile microwave hydrothermal process with H2O as solvent. Crystal field modulation and band gap doping by Mn2+ substitution for Zn2+ realizes color tunable Mn2+ emission from 424 to 535 nm. Mn2+‐doping on the phase and size transition of Zn2GeO4 nanocrystals was discussed, and a possible Zn2GeO4 : xMn crystal growth mechanism is discussed. Photoluminescence (PL) spectra indicate that the d‐d transition of manganese ions (4T1→6A1) corresponds to a strong green emission of Zn2GeO4 : xMn phosphors.