Electrochemical determination of levofloxacin with a Cu–metal–organic framework derivative electrode

Journal of Materials Science: Materials in Electronics - Levofloxacin (LEV) is used in pharmaceuticals to treat bacterial infections, but is rarely metabolized by the human body, and hence, largely...     

Hierarchical build-up of bio-based nanofibrous materials with tunable metal–organic framework biofunctionality

Multifunctional, light-weight, responsive materials show promise in a range of applications including soft robotics, therapeutic delivery, advanced diagnostics and charge storage. This paper presents a novel, scalable, efficient and sustainable approach for the preparation of cellulose nanofibril-based aerogels via a facile ice-templating, solvent exchange and air-drying procedure, which could replace existing inefficient drying processes. These ambient-dried aerogels (∼99% porosity) exhibit a high specific compressive modulus (26.8 ± 6.1 kPa m³ kg⁻¹, approaching equivalence of carbon-nanotube-reinforced aerogels), wet stability and shape recovery (80–90%), favorable specific surface area (90 m² g⁻¹) and tunable densities (2–20 kg m⁻³). The aerogels provide an ideal nanofibrillar substrate for in-situ growth of metal–organic frameworks (MOFs), via co-assembly of MOF precursors with proteins in aqueous solutions. The resulting hybrid aerogels show a nine-fold increase in surface area (810 m²g⁻¹), with preserved wet stability and additional protein biofunctionality. The hybrid aerogels facilitate a pH-controlled release of immobilized proteins, following a concomitant disassembly of the surface grown MOFs, demonstrating their use in controlled delivery systems. The colorimetric protein binding assay of the biofunctionalized hybrid aerogel also demonstrates the potential of the material as a novel 3D bioassay platform, which could potentially be an alternative to plate-based enzyme-linked immunosorbent assay.     

Synthesis and characterization of an energetic three-dimensional metal–organic framework with blue photoluminescence

A new inorganic–organic hybrid lead(II) coordination polymer [PbCl(tza)]_n (Htza = tetrazole-1-acetic acid) has been synthesized under hydrothermal condition. The complex was characterized by elemental analysis, FT-IR spectroscopy, single-crystal X-ray analysis, thermogravimetric analysis (TG) and differential scanning calorimetry thermal analysis (DSC). The Pb(II) centers are connected through both the tza and Cl^? bridging ligands to form a three-dimensional metal–organic framework (MOF). The compound has been found to exhibit blue photoluminescence in the solid state at room temperature and may be good candidates for photoactive materials. DSC thermal analysis shows the complex is an energetic coordination compound and tza can be used as an energetic ligand.     

Parts-per-billion (ppb) selective iodine sensors leveraging metal–organic framework nanoenvironment

Ultra-sensitive and highly selective iodine gas sensors play a crucial role during the nuclear radiation leak for a timely detection and mitigation of pollution, ensuring the safety of a vast number of operators and subsequent integrity of the facility. Herein, we rationally designed a metal–organic framework (MOF) that exhibits an outstanding performance with an almost billionfold enhancement in the electrical response due to its optimized hydrophobicity, which allows the easy migration of iodine molecules through the channels and the presence of suitable interaction sites, temporarily anchoring the target molecule for ultra-trace sensing. The prototype sensor tested in demanding environments demonstrates its high selectivity, ultra-trace parts per billion (ppb)-level sensitivity, good reversibility, and a very fast response time even at high frequencies compared to existing adsorbents, including commercially available materials. Further, the iodine sensing at the atomic level was studied in detail by measuring the electrical response of a single crystal and, the optimal thickness of the MOF layer was identified for an industrially-viable prototype sensor by using inkjet printing. In a wider perspective, we propose a general strategy for engineering electrically efficient sensing materials that will enable the construction of high-sensitivity iodine sensors targeting a safe and sustainable future.     

A green route approach to the synthesis of Ni(II) and Zn(II) templated metal–organic frameworks

A new synthetic route involving mixing of solid reactants followed by heating has been developed for the preparation of two templated metal–organic frameworks (MOFs). [Ni(NO₃)₂(bipy)₂](pyrene)₂ (1) was obtained by mixing together Ni(NO₃)₂·6H₂O, 4,4-bipyridine and pyrene followed by heating at 85 °C for 4 h, while [Zn₂(fumarate)₂(bipy)] (2) was synthesized by mixing together Zn(O₂CCH₃)₂·2H₂O, fumaric acid and 4,4-bipyridine followed by heating at 160 °C for 16 h. The materials were characterized by elemental analysis, FT-IR spectroscopy and X-ray powder diffraction analysis (XRPD). Comparison of XRPD patterns of the materials with patterns simulated from the single crystal X-ray diffraction data, obtained from Cambridge Structural database, allowed identification of the products. Conversion of solid reactants to MOFs occurs spontaneously even when reactants are not mechanically stressed. Overall, the study suggests that MOFs can be synthesized in solid state simply by mixing together appropriate reactants without co-mill (ball-mill). Compared with traditional synthetic techniques such as solvothermal, ball-milling and solution-based, this method is environmentally friendly and highly efficient in the manufacture of these MOFs on a large scale.     

Tannin-immobilized mesoporous silica bead (BT–SiO2) as an effective adsorbent of Cr(III) in aqueous solutions

This study describes a new approach for the preparation of tannin-immobilized adsorbent by using mesoporous silica bead as the supporting matrix. Bayberry tannin-immobilized mesoporous silica bead (BT–SiO₂) was characterized by powder X-ray diffraction to verify the crystallinity, field-emission scanning electron microscopy to observe the surface morphology, and surface area and porosity analyzer to measure the mesoporous porous structure. Subsequently, the adsorption experiments to Cr(III) were applied to evaluate the adsorption performances of BT–SiO₂. It was found that the adsorption of Cr(III) onto BT–SiO₂ was pH-dependent, and the maximum adsorption capacity was obtained in the pH range of 5.0–5.5. The adsorption capacity was 1.30 mmol g^?1 at 303 K and pH 5.5 when the initial concentration of Cr(III) was 2.0 mmol L^?1. Based on proton nuclear magnetic resonance (HNMR) analyses, the adsorption mechanism of Cr(III) on BT–SiO₂ was proved to be a chelating interaction. The adsorption kinetic data can be well described using pseudo-first-order model and the equilibrium data can be well fitted by the Langmuir isothermal model. Importantly, no bayberry tannin was leached out during the adsorption process and BT–SiO₂ can simultaneously remove coexisting metal ions from aqueous solutions. In conclusion, this study provides a new strategy for the preparation of tannin-immobilized adsorbents that are highly effective in removal of heavy metals from aqueous solutions.     

Facile synthesis and morphology control of zeolite MCM-22 via a two-step sol–gel route with tetraethyl orthosilicate as silica source

MCM-22 zeolite was synthesized via a two-step sol–gel route (low pH sol–gel reaction followed by high pH crystallization) under static hydrothermal conditions using tetraethyl orthosilicate (TEOS) as silica source. Various parameters that significantly influence the synthesis results during both the hydrolysis reaction of TEOS in acid media and the hydrothermal reaction in base media were investigated in detail. The produced samples were characterized by XRD, ICP, and SEM techniques. It is found that pure MCM-22 with high crystallinity can be obtained via the novel two-step sol–gel route in a broad window of reaction conditions. The increase of temperature and pH value for the hydrolysis of TEOS favors the shortening of crystallization time and decreasing of MCM-22 particle size. Moreover, by adjusting the hydrothermal reaction parameters, such as increasing the crystallization temperature, increasing the alkalinity of the synthesis gel mixture, and decreasing the SiO₂/Al₂O₃ ratio, the crystallization is accelerated substantially. Also, rose-like or lamellar-like morphologies of MCM-22 particles with different sizes can be achieved by changing these reaction parameters. Using this two-step sol–gel route, MCM-22 is able to be well produced in a wide range of the SiO₂/Al₂O₃ ratio from 20 to 100.     

Study of the microstructure and thermomechanical properties of Mo/graphite joint brazed with Ti–Zr–Nb–Be powder filler metal

Journal of Materials Science - The aim of this work was to braze molybdenum and graphite with Ti–40Zr–8.5Nb–1.5Be filler metal in order to demonstrate the possibility of its...     

Electrodeposition of chromium coatings from sulfate–carbamide electrolytes based on Cr(III) compounds

We propose an electrolyte based on chromium sulfate (1 mole/liter Cr(III)) and containing both formic acid and carbamide (urea). This electrolyte enables one to get Cr coatings with a thickness of several micrometers. It is shown that the current yield and deposition rate increase as the current density and pH value increase and temperature decreases. We select the optimal conditions of electrolysis under which bright high-quality chromium deposits are obtained. In this case, the deposition rate of the metal varies from 0.5 to 1.5 μm/min. It is shown that the optimal concentration of both formic acid and carbamide is equal to 0.5 mole/liter. The necessity of using certain surface-active substances to prevent the formation of pitting on the surface of the deposit is demonstrated. Moreover, it is discovered that the microhardness of Cr deposits attains its highest values (950–980kg/mm²) for currents with densities of 30–35 A⋅dm⁻² and decreases as the pH value and temperature increase. Electrolysis is realized by using titanium–manganese-dioxide anodes and, hence, it is not necessary to separate the cathodic and anodic spaces.     

TiO_2-Fe_3O_4/MIL-101(Cr)磁性复合光催化材料的制备及其光催化性能

采用原位水热法合成了TiO_2-Fe_3O_4/MIL-101(Cr)磁性复合光催化材料,利用XRD、SEM、UV-Vis DRS、BET和磁学测量系统对复合光催化材料的结构和性能进行了表征,并以亚甲基蓝(MB)为模拟污染物,研究了该复合光催化材料的可见光催化活性,并考察了光催化材料的稳定性。结果表明:巯基官能化的Fe_3O_4和TiO_2与MIL-101(Cr)结合成功,复合后的TiO_2-Fe_3O_4/MIL-101(Cr)光催化材料的可见光响应范围得到明显拓宽;当TiO_2的添加量为400mg时所制得的磁性复合光催化材料具有相对较好的光催化降解效果,经过120min光照后,对MB的去除率高达80%;该磁性复合光催化材料具有良好的稳定性和磁分离性能。     

A facile synthesis of graphene–metal (Pb, Zn, Cd, Mn) sulfide composites

We propose a general approach for the preparation of graphene-metal sulfide quantum dots (QDs) composites by π–π stacking of pyridine-capped metal sulfide QDs and chemically converted graphene (CCG) in aqueous solution. CCG sheets disperse stably in water without the assistance of dispersing agents, only by electrostatic repulsion. The aromatic structures of pyridine capped on metal sulfide QDs make these QDs dispersible in ethanol or water, and further introduce a π–π stacking interaction between CCG and QDs, and extend the conjugated structure of CCG. The structural details, formation mechanism, and textural properties of the resultant graphene-metal sulfide QDs composites are characterized by X-ray diffraction, UV–vis absorption, electron microscopy, and Raman scattering studies. The CCG–metal sulfide composites disperse stably in aqueous solution, allowing them to be potentially used in biological tissues and easy-to-form filtered films for further research and application.     

Unusual photoluminescence of Cu–ZnO and its correlation with photocatalytic reduction of Cr(VI)

Cu–ZnO was synthesized by sol–gel route with a varied copper concentration of 1, 2 and 3 mol%. The synthesized materials were structurally characterized with powder X-ray diffraction and Raman spectroscopy, morphologically using a field emission scanning electron microscope, and electronic properties were studied with UV–visible spectroscopy and photoluminescence spectroscopy. Variation in Cu doping showed enhancement/quenching in photoluminescence of ZnO. This special characteristic is reflected in photocatalytic reduction of Cr(VI).     

Recent advances in the synthesis of nanoscale hierarchically porous metal–organic frameworksOA

Nanoscale hierarchically porous metal–organic frameworks(NHP-MOFs) have received unprecedented attention in many fields owing to their integration of the strengths of nanoscale size(<1 μm) and hierarchical porous structure(micro-, meso-and/or macro-pores) of MOFs. This review focuses on recent advances in the main synthetic strategies for NHP-MOFs based on different metal ions(e.g., Cu, Fe, Co, Zn, Al, Zr, and Cr), including the template method, composite technology, post-synthetic modificati...     

Study of impregnation of poly(l-lactide-ran-ε-caprolactone) copolymers with useful compounds in supercritical carbon dioxide

Outstanding controlled release materials were developed using statistically random copolymers of l-lactide (l-LA) with ε-caprolactone (CL) using Sn(oct)₂ as a catalyst at 150 °C for 24 h without solvent. Preparation of novel controlled release materials was carried out using useful organic compounds with low boiling points and synthetic random copolymers composed of l-LA and CL as base materials under supercritical carbon dioxide (scCO₂). Low-boiling-point compounds such as d-limonene, hinokitiol, and trans-2-hexenal were used. In impregnation experiments using scCO₂, the amounts of low-boiling-point compounds increased with an increase in l-LA content. When enzymatic degradation of poly(l-LA-ran-CL) was performed using lipase PS, copolymers with higher CL contents degraded more rapidly than did copolymers with higher l-LA content. In contrast, enzymatic degradation of copolymers occurred to a higher degree with increased l-LA content in enzymatic degradation by proteinase K. In a controlled release experiment with poly(l-LA-ran-CL) (=73/27), after 400 h of degradation by proteinase K, the remaining weight of the copolymer pellet was 6% and the amount of d-limonene remaining in the pellet was 15%.     

Highly efficient removal of trace lead(Ⅱ)from wastewater by 1,4-dicarboxybenzene modified Fe/Co metal organic nanosheets

A novel Fe/Co metal organic complex nanosheet modified by 1,4-dicarboxybenzene(BDC),i.e.,FeCo@BDC,was prepared,and highly efficient removal performance for trac...     

Effect of (Co–TeO2-doped polyvinylpyrrolidone) organic interlayer on the electrophysical characteristics of Al/p-Si (MS) structures

Journal of Materials Science: Materials in Electronics - In this paper, (Co–TeO2) nanostructures were synthesized using the microwave-assisted method for the fabrication of...