Nanocomposites with ZrO2@S-Doped g-C3N4 as an Enhanced Binder-Free Sensor: Synthesis and Characterization.

This study describes new electrocatalyst materials that can detect and reduce environmental pollutants. The synthesis and characterization of semiconductor nanocomposites (NCs) made from active ZrO2@S-doped g-C3N4 is presented. Electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) measurements were used to examine electron transfer characteristics of the synthesized samples. Using X-ray diffraction (XRD) and high-resolution scanning electron microscopy (HR-SEM) techniques, inclusion of monoclinic ZrO2 on flower-shaped S-doped-g-C3N4 was visualized. High-resolution X-ray photoelectron spectroscopy (XPS) revealed successful doping of ZrO2 into the lattice of S-doped g-C3N4. The electron transport mechanism between the electrolyte and the fluorine tin-oxide electrode (FTOE) was enhanced by the synergistic interaction between ZrO2 and S-doped g-C3N4 as co-modifiers. Development of a platform with improved conductivity based on an FTOE modified with ZrO2@S-doped g-C3N4 NCs resulted in an ideal platform for the detection of 4-nitrophenol (4-NP) in water. The electrocatalytic activity of the modified electrode was evaluated through determination of 4-NP by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) under optimum conditions (pH 5). ZrO2@S-doped g-C3N4 (20%)/FTOE exhibited good electrocatalytic activity with a linear range from 10 to 100 µM and a low limit of detection (LOD) of 6.65 µM. Typical p-type semiconductor ZrO2@S-doped g-C3N4 NCs significantly impact the superior detection of 4-NP due to its size, shape, optical properties, specific surface area and effective separation of electron-hole pairs. We conclude that the superior electrochemical sensor behavior of the ZrO2@S-doped g-C3N4 (20%)/FTOE surfaces results from the synergistic interaction between S-doped g-C3N4 and ZrO2 surfaces that produce an active NC interface.

Synthesis and characterization of CuO@S-doped g-C3N4 based nanocomposites for binder-free sensor applications.

This study presents the simultaneous exfoliation and modification of heterostructured copper oxide incorporated sulfur doped graphitic carbon nitride (CuO@S-doped g-C3N4) nanocomposites (NCs) synthesized via chemical precipitation and pyrolysis techniques. The results revealed that the approach is feasible and highly efficient in producing 2-dimensional CuO@S-doped g-C3N4 NCs. The findings also showed a promising technique for enhancing the optical and electrical properties of bulk g-C3N4 by combining CuO nanoparticles (NPs) with S-doped g-C3N4. The crystallite and the average size of the NCs were validated using X-ray diffraction (XRD) studies. Incorporation of the cubical structured CuO on flower shaped S-doped-g-C3N4 was visualized and characterized through XRD, HR-SEM/EDS/SED, FT-IR, BET, UV-Vis/DRS, PL, XPS and impedance spectroscopy. The agglomerated NCs had various pore sizes, shapes and nanosized crystals, while being photo-active in the UV-vis range. The synergistic effect of CuO and S-doped g-C3N4 as co-modifiers greatly facilitates the electron transfer process between the electrolyte and the bare glassy carbon electrode. Specific surface areas of the NCs clearly revealed modification of bulk S-doped g-C3N4 when CuO NPs are incorporated with S-doped g-C3N4, providing a suitable environment for the binder-free decorated electrode with sensing behavior for hazardous pollutants. This was tested for the preparation of a 4-nitrophenol sensor.

Spectroscopic Behaviour of Copper(II) Complexes Containing 2-Hydroxyphenones.

Theoretical investigations by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods shed light on how the type of ligand or attached groups influence the electronic structure, absorption spectrum, electron excitation, and intramolecular and interfacial electron transfer of the Cu(II) complexes under study. The findings provide new insight into the designing and screening of high-performance dyes for dye-sensitized solar cells (DSSCs).

Trans-Cis Kinetic Study of Azobenzene-4,4'-dicarboxylic Acid and Aluminium and Zirconium Based Azobenzene-4,4'-dicarboxylate MOFs.

Metal organic frameworks (MOFs) are porous hybrid crystalline materials that consist of organic linkers coordinated to metal centres. The trans-cis isomerisation kinetics of the azobenzene-4,4'-dicarboxylic acid (AZB(COOH)2) precursor, as well as the Al3+ (Al-AZB)- and Zr4+ (Zr-AZB)-based MOFs with azobenzene-4,4'-dicarboxylate linkers, are presented. The photo-isomerization in the MOFs originates from singly bound azobenzene moieties on the surface of the MOF. The type of solvent used had a slight effect on the rate of isomerization and half-life, while the band gap energies were not significantly affected by the solvents. Photo-responsive MOFs can be classified as smart materials with possible applications in sensing, drug delivery, magnetism, and molecular recognition. In this study, the MOFs were applied in the dye adsorption of congo red (CR) in contaminated water. For both MOFs, the UV-irradiated cis isomer exhibited a slightly higher CR uptake than the ambient-light exposed trans isomer. Al-AZB displayed a dye adsorption capacity of over 95% for both the UV-irradiated and ambient light samples. The ambient light exposed Zr-AZB, and the UV irradiated Zr-AZB had 39.1% and 44.6% dye removal, respectively.

Dye adsorption of aluminium- and zirconium-based metal organic frameworks with azobenzene dicarboxylate linkers.

The high efficiency of metal-organic-frameworks (MOFs) such as the ZIF, MIL and UiO type species in dye adsorption is well established. Recently, an emerging class of photoresponsive azobenzene-based MOFs has found suitable application in gas adsorption. However, there is a dearth of research on their use in the adsorption of dyes and other water pollutants. In this research, two microporous photoresponsive azobenzene dicarboxylate MOFs of Al3+ (Al-AZB) and Zr4+ (Zr-AZB) were synthesized for the adsorption of congo red (CR) dye. The surface and textural properties of the synthesized MOFs were characterized by FTIR, PXRD, SEM, TGA, BET and pore analysis. Both MOFs were crystalline, thermally stable up to 300 °C and stable in aqueous medium at room temperature. The Al-AZB displayed a higher surface area (2718 m2/g) than the Zr-AZB (1098 m2/g), which significantly impacted the higher adsorption of CR. Besides, pore volumes of 0.86 cm3/g and 0.35 cm3/g were obtained for Al-AZB and Zr-AZB, respectively. The maximum adsorption capacity of Al-AZB and Zr-AZB was 456.6 mg/g and 128.9 mg/g, respectively, with the former superior to other potent adsorbents. The pseudo-second-order and Langmuir models were well correlated with the dye uptake on the MOFs. Thermodynamics revealed random and endothermic sorption of CR dominated by chemisorption, while efficient regeneration and reuse of both MOFs were achieved using dimethylformamide as eluent. The results proved the potency of the synthesized photoresponsive MOFs, as highly efficient and reusable materials for dye adsorption.

Metal Exchange of ZIF-8 and ZIF-67 Nanoparticles with Fe(II) for Enhanced Photocatalytic Performance.

Zeolitic imidazolate frameworks (ZIFs), such as ZIF-8 and ZIF-67, were found to be efficient catalysts. However, ZIFs are not used much in photocatalysis due to their low photocatalytic activity for most reactions. The photocatalytic activity can be improved by modifying the framework by exchanging the Zn(II) ions (ZIF-8) and Co(II) ions (ZIF-67) with a more photocatalytically active metal(II) ion to form an efficient bimetallic ZIF photocatalyst. Redox-active iron (Fe)-based materials are known to be highly potent photocatalysts. Thus, incorporating iron into ZIFs could significantly enhance their photocatalytic performance. In this study, we modified nanosized ZIF-8(Zn) and ZIF-67(Co) via metal (Fe2+) exchange to produce bimetallic frameworks that are photocatalytically more active than their parent ZIFs. Nanosized ZIF-8 and ZIF-67 were synthesized isothermally in either water or methanol under ambient conditions. From these, Fe-containing bimetallic ZIF-8 and ZIF-67 nanoparticles were synthesized via the metal exchange, and their performance on the photocatalytic degradation of dye was evaluated. The morphology and crystal structures of the pristine ZIF-8 and ZIF-67 nanoparticles were retained to a large extent during the iron exchange. Their Brunauer-Emmett-Teller (BET) surface areas decreased by less than 15% for nZIF-8 and less than 12% for nZIF-67. The binding energy values on X-ray photoelectron spectroscopy (XPS) confirmed the preservation of the oxidation state of Fe(II) during the exchange process. A remarkably higher catalytic activity was observed for the photocatalytic degradation of dye by the Fe-exchanged nZIF-8 and nZIF-67 compared to their parent ZIFs. This proved that the incorporation of Fe(II) centers into the ZIF framework enhanced the photocatalytic activity of the framework dramatically. In addition, these catalysts can be regenerated and reused without an appreciable loss in activity.

Correction to "Optimized CO2 Capture of the Zeolitic Imidazolate Framework ZIF-8 Modified by Solvent-Assisted Ligand Exchange".

[This corrects the article DOI: 10.1021/acsomega.1c01130.].

DFT data to relate calculated LUMO energy with experimental reduction potentials of Cu(II)-ß-diketonato complexes.

We present data on the computed lowest unoccupied molecular orbital energy (ELUMO ) of two series of Cu(II)-ß-diketonato complexes, calculated via density functional theory (DFT). These are correlated to experimental reduction potential data (E pc), obtained by cyclic voltammetry under different experimental conditions (solvent, working and reference electrodes). All calculations were done with the B3LYP functional in the gas phase. Knowledge of the influence of different ligands on the redox potential of copper complexes, as measured by DFT calculated energy data, are very useful. These theoretical correlations are vital in the further design of similar compounds, to be customized for specific applications. The correlations can be used to predict and fine-tune redox potentials prior to synthesis, saving experimental chemists time and laboratory expenses. Redox potentials influence the catalytic property of bis(ß-diketonato)copper(II) compounds. New catalysts can therefore be customized with a specific reduction potential and catalytic activity. Further, the Cu(II/I) redox couple is a potential alternative as electrolyte for dye-sensitized solar cells [1], [2], [3]. The redox potential of the electrolyte can drastically affect the photovoltage output and should therefore be optimized for efficiency and durability. By adjusting the reduction potential via different ligands on the complex, the properties of copper dyes can be fine-tuned at molecular level. For more insight into the reported data, see the related research article "Synthesis, Characterization, DFT and Biological Activity of Oligothiophene ß-diketone and Cu-complexes" published in Polyhedron [4].

Optimized CO2 Capture of the Zeolitic Imidazolate Framework ZIF-8 Modified by Solvent-Assisted Ligand Exchange.

Zeolitic imidazolate frameworks, like ZIF-8 and related structures, have shown great potential for the capture of carbon dioxide. Modifying their structure by exchanging part of the constituent organic ligands is a proven method for enhancing the capacity to absorb CO2. In this work, we performed solvent-assisted ligand exchange (SALE) on nanosized ZIF-8 (nZIF-8) with a series of functionalized imidazole derivatives (exchange percentages, after 24 h): 2-bromoimidazole (19%), 2-chloroimidazole (29%), 2-trifluoromethylbenzimidazole (4%), 2-mercaptobenzimidazole (4%), and 2-nitroimidazole (54%). The sodalite topology and porosity of nZIF-8 were maintained with all SALE modifications. Low-pressure CO2 adsorption of nZIF-8 (38.5 cm3 g-1) at STP was appreciably enhanced with all mixed-linker SALE products. Using halogenated (-Cl, -Br, and -CF3) imidazole derivatives in a 24 h SALE treatment resulted in increases between 11 and 22% in CO2 adsorption, while the thiol (-SH)- and nitro (-NO2)-functionalized SALE products led to 32 and 100% increases in CO2 uptakes, respectively. These CO2 uptakes were further optimized by varying the SALE treatment time. The SHbIm- and NO2Im-exchanged SALE products of nZIF-8 show 87 and 98 cm3 g-1 of CO2 uptakes after 60 and 120 h of SALE, respectively. These are record high CO2 adsorptions for all reported ZIF derivatives at low-pressure conditions.

Superior cytotoxicity of hydrophylic gold carboxylato complexes over hydrophylic silver carboxylates.

BACKGROUND: The water-soluble ionic gold(I) complex [Au(PPh(2)CH(2)CH(2)PPh(2))(2)]Cl possesses at least ten times stronger antineoplastic activity than the water-soluble neutral silver(I) carboxylates [AgO(2)C(CH(2)OCH(2))(n)H], 1, (n=1), 2 (n=2), or 3 (n=3) even though Au(I) and Ag(I) are isoelectronic d(10) metals lying one above the other in the periodic table of the elements. In this study we determined the cytotoxicity of the stable water-soluble gold(I) carboxylates [(Ph(3)P)AuO(2)C(CH(2)OCH(2))(n)H], 4 (n=1), 5 (n=2) and 6 (n=3) to compare the intrinsic antineoplastic activity of gold(I) and silver(I) under conditions where different complex charges do not influence the result. MATERIALS AND METHODS: The cytotoxicity of carboxylato gold complexes 4-6 towards the HeLa (human cervix epithelioid) cancer cell line ATCC CCL-2, resting lymphocytes and phytohaemagglutinin(PHA)-stimulated lymphocytes were determined. Cell survival was measured by means of the colorimetric 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide (MTT) assay. RESULTS: The IC(50) values of 4-6 from six experiments causing 50% cell growth inhibition were essentially constant; values ranged between 0.50 and 0.82 µmol dm(-3). Drug activity was thus independent of the carboxylato ligand chain length. Metal complexes 4-6 were at least one order of magnitude more cytotoxic towards the HeLa cancer cell line than the silver carboxylates 1-3 and were almost as cytotoxic as [Au(PPh(2)CH(2)CH(2)PPh(2))(2)]Cl and cisplatin [(H(3)N)(2)PtCl(2)]. Complexes 4-6 were also 2-5 times more toxic against PHA-stimulated lymphocyte cultures than to HeLa cancer cell. CONCLUSION: Unlike for the silver complexes 1-3, no meaningful drug activity-structural relationship exists for the gold(I) d(10) carboxylates 4-6. Gold(I) complexes in neutral and charged form are intrinsically more cytotoxic than silver(I) against the HeLa cancer cell line.