Fe(III)-incorporated porphyrin-based conjugated organic polymer as a peroxidase mimic for the sensitive determination of glucose and H2O2.

Nanozymes, i.e., nanomaterials that possess intrinsic enzyme-like behaviour, have thrived over the past few decades owing to their advantages of superior stability and effortless storage. Such artificial enzymes can be a perfect alternative to naturally occurring enzymes, which have disadvantages of high cost and limited functionality. In this work, we present the fabrication of an Fe(III)-incorporated porphyrin-based conjugated organic polymer as a nanozyme for the efficient detection of glucose through its intrinsic peroxidase activity and the amperometric detection of hydrogen peroxide. The iron-incorporated porphyrin-based conjugated organic polymer (Fe-DMP-POR) possesses a spherical morphology with high chemical and thermal stability. Exploiting the peroxidase-mimicking activity of the material for the determination of glucose, a detection limit of 4.84 µM is achieved with a linear range of 0-0.15 mM. The Fe-DMP-POR also exhibits a reasonable recovery range for the detection of human blood glucose. The as-synthesized material can also act as an H2O2 sensor, with a sensitivity of 947.67 µA cm-2 mM-1 and a limit of detection of 3.16 µM.

Copper Immobilized over 2D Hexagonal SBA-15 for Electrochemical and Colorimetric Sulfite Sensing.

Sulfite (SO32-) is considered a highly toxic anion for living organisms. Herein, we report the synthesis of copper immobilized over a 2D hexagonally ordered mesoporous silica material CuMS as an electrochemical and colorimetric dual-technique-based sensing platform for sulfite detection. The immobilization of copper on silica was achieved through the bis[3-(triethoxysilyl)propyl]tetrasulfide (TEPTS) ligand. Morphological and physical properties of the material were confirmed by several characterization techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 sorption, and X-ray photoelectron spectroscopy. The CuMS material retained mesoporosity with a narrow pore size distribution (D ≈ 5.4 nm) and a high Brunauer-Emmett-Teller surface area of 682 m2 g-1 after the immobilization of copper. The prepared catalyst shows promising electrocatalytic activity toward sulfite oxidation. A linear variation in the peak current was obtained for SO32- oxidation in the 0.2-15 mM range with a high sensitivity of 62.08 µA cm-2, under optimum experimental conditions. The limit of detection (LOD) was found to be 1.14 nM. CuMS also shows excellent activity toward colorimetric detection of sulfite anions with an LOD of 0.4 nM. The proposed sensor shows high selectivity toward the sulfite anion, even in the presence of common interferents. The detection of sulfite in white wine with excellent recovery demonstrates the practical applicability of this sensor.

Ni(II)-Incorporated Porphyrin-Based Conjugated Porous Polymer Derived from 2,6-Diformyl-4-methylphenol as a Catalyst for the Urea Oxidation Reaction.

The urea oxidation reaction (UOR) is an excellent alternative to the sluggish oxygen evolution reaction (OER) as an anode reaction for hydrogen generation via electrochemical water splitting. Here, a porphyrin-based conjugated porous polymer (CPP) has been developed through the polycondensation reaction of 2,6-diformyl-4-methylphenol and pyrrole (DMP-POR). The nickel(II) complex of this conjugated polymer Ni-DMP-POR shows efficient UOR in an alkaline medium. The as-synthesized materials were characterized by solid-state 13C CP-MAS, thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The porous property of the materials was characterized by N2 adsorption/desorption isotherms at 77 K. Both DMP-POR and Ni-DMP-POR showed excellent thermal stability. The Ni-DMP-POR exhibits very good UOR in 1 M KOH and 0.33 M urea with an overpotential of 260 mV at 10 mA cm-2 and a Tafel slope of 48 mV dec-1. The catalyst also shows excellent chronoamperometric and chronopotentiometric stability, suggesting its future scope in sustainable hydrogen production from wastewater resources.

Metal-Thiolate Framework for Electrochemical and Photoelectrochemical Hydrogen Generation.

Hydrogen has evolved as the cleanest and most sustainable fuel, produced directly from naturally abundant water resources. Generation of hydrogen by electrochemical or photoelectrochemical splitting of water has been conceived as the most effective method for hydrogen production. Herein, a robust solid metal-thiolate framework (MTF-1) was obtained by hydrothermal crystallization of the reaction mixture consisting of 1,3,5-triazine-2,4,6-trithioltrisodium salt and CuII under mild synthesis conditions. The material was thoroughly characterized and explored as efficient catalyst for electrochemical and photoelectrochemical hydrogen evolution reaction (HER) via water splitting reactions. MTF-1 showed onset potential 0.045 VRHE and overpotential η(@10 mA cm-2 ) at 0.096 VRHE . The electrochemical surface area of MTF-1 was found to be 509 m2 g-1 . The photo current density at pH 5.0 was found to be 0.487 mA cm-2 at 0.6 VRHE . The feasibility of the reaction pathway was correlated from the density function theory study, which suggested the complete downhill energetics indicating spontaneous electrochemical hydrogen generation in the acidic medium.

Green synthesis of C5-C6-unsubstituted 1,4-DHP scaffolds using an efficient Ni-chitosan nanocatalyst under ultrasonic conditions.

A heterogeneous and magnetically recyclable Ni-chitosan nanocatalyst was synthesized and thoroughly characterized by powder Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) spectroscopy, etc. It was effectively utilized in the eco-friendly synthesis of new C5-C6-unsubstituted 1,4-DHPs under ultrasonic irradiation. The important focus of the methodology was to develop an environmentally friendly protocol with a short reaction time and a simple reaction procedure. The other advantages of this protocol are a wide substrate scope, a very good product yield, the use of an eco-friendly solvent and a recyclable nanocatalyst, as well as reaction at room temperature.

Correction: Thiadiazole containing N- and S-rich highly ordered periodic mesoporous organosilica for efficient removal of Hg(II) from polluted water.

Correction for 'Thiadiazole containing N- and S-rich highly ordered periodic mesoporous organosilica for efficient removal of Hg(II) from polluted water' by Asim Baumik et al., Chem. Commun., 2020, 56, 3963-3966, DOI 10.1039/D0CC00407C.

Transformation of Wurtzite ZnO to a New Triclinic Nanoporous ZnO Phase via Hydrothermal Treatment with Metformin for Designing Proton Conducting Material.

Zinc oxide is one of the most widely studied semiconductor metal oxides, which predominantly crystallizes as hexagonal wurtzite and often cubic zinc-blende phases. Here we report the transformation of the highly stable wurtzite ZnO to a new triclinic phase NZO-2 by using metformin as a template during post-synthesis hydrothermal treatment. This crystalline phase of the material NZO-2 has been identified through the refinement of the powder XRD data. NZO-2 possesses porous rod like particle morphology consisting of the self-assembly of 3-7 nm size spherical nanoparticles and interparticle nanoscopic voids spaces. NZO-2 has been surface phosphorylated and the resulting material displayed good proton conductivity. Further, NZO-2 displayed ultra-low band gap of 1.74 eV, thereby responsible for red emission under high energy laser excitation and this may open new opportunities in optoelectronic application of ZnO.

Metformin-Templated Nanoporous ZnO and Covalent Organic Framework Heterojunction Photoanode for Photoelectrochemical Water Oxidation.

Photoelectrochemical water-splitting offers unique opportunity in the utilization of abundant solar light energy and water resources to produce hydrogen (renewable energy) and oxygen (clean environment) in the presence of a semiconductor photoanode. Zinc oxide (ZnO), a wide bandgap semiconductor is found to crystallize predominantly in the hexagonal wurtzite phase. Herein, we first report a new crystalline triclinic phase of ZnO by using N-rich antidiabetic drug metformin as a template via hydrothermal synthesis with self-assembled nanorod-like particle morphology. We have fabricated a heterojunction nanocomposite charge carrier photoanode by coupling this porous ZnO with a covalent organic framework, which displayed highly enhanced photocurrent density of 0.62 mA/cm2 at 0.2 V vs. RHE in photoelectrochemical water oxidation and excellent photon-to-current conversion efficiency at near-neutral pH vis-à-vis bulk ZnO. This enhancement of the photocurrent for the porous ZnO/COF nanocomposite material over the corresponding bulk ZnO could be attributed to the visible light energy absorption by COF and subsequent efficient charge-carrier mobility via porous ZnO surface.

Thiadiazole containing N- and S-rich highly ordered periodic mesoporous organosilica for efficient removal of Hg(ii) from polluted water.

A new N- and S-rich highly ordered periodic mesoporous organosilica material DMTZ-PMO bearing thiadiazole and thiol moieties inside the pore-wall of a 2D-hexagonal nanomaterial has been synthesized. DMTZ-PMO shows a very high surface area (971 m2 g-1), and can be used for efficient and fast removal of Hg2+ from polluted water with a very high Hg2+ uptake capacity of 2081 mg g-1.

Folic acid-conjugated magnetic mesoporous silica nanoparticles loaded with quercetin: a theranostic approach for cancer management.

The development of drug carriers based on nanomaterials that can selectively carry chemotherapeutic agents to cancer cells has become a major focus in biomedical research. A novel pH-sensitive multifunctional envelope-type mesoporous silica nanoparticle (SBA-15) was fabricated for targeted drug delivery to human colorectal carcinoma cells (HCT-116). SBA-15 was functionalized with folic acid (FA), and the material was loaded with the water-insoluble flavonoid, quercetin (QN). Additionally, acid-labile magnetite Fe3O4 nanoparticles were embedded over the FA-functionalized QN-loaded monodisperse SBA-15 to prepare the highly orchestrated material FA-FE-SBA15QN. The in vitro and in vivo anti-carcinogenic efficacy of FA-FE-SBA15QN was carried out to explore the pH-sensitive QN release with putative mechanistic aspects. FA-FE-SBA15QN caused a marked tumor suppression, and triggered mitochondrial-dependent apoptosis through a redox-regulated cellular signaling system. Furthermore, FA-IO-SBA-15-QN initiated the c-Jun N-terminal Kinase (JNK)-guided H2AX phosphorylation, which relayed the downstream apoptotic signal to the phosphorylate tumor suppressor protein, p53. On the other hand, the selective inhibition of heat shock protein-27 (HSP-27) by FA-FE-SBA15QN augmented the apoptotic fate through JNK/H2AX/p53 axis. The in vitro and in vivo magnetic resonance imaging (MRI) studies have indicated the theranostic perspective of the composite. Thus, the result suggested that the newly synthesized FA-FE-SBA15QN could be used as a promising chemo theranostic material for the management of carcinoma.

General synthesis of hierarchical sheet/plate-like M-BDC (M = Cu, Mn, Ni, and Zr) metal-organic frameworks for electrochemical non-enzymatic glucose sensing.

Two-dimensional metal-organic frameworks (2D MOFs) are an attractive platform to develop new kinds of catalysts because of their structural tunability and large specific surface area that exposes numerous active sites. In this work, we report a general method to synthesize benzene dicarboxylic acid (BDC)-based MOFs with hierarchical 3D morphologies composed of 2D nanosheets or nanoplates. In our proposed strategy, acetonitrile helps solvate the metal ions in solution and affects the morphology, while polyvinylpyrrolidone (PVP) serves as a shape-control agent to assist in the nucleation and growth of MOF nanosheets. PVP also acts as a depletion agent to drive the assembly of the hierarchical sheet/plate-like M-BDC under solvothermal conditions. Further, we also demonstrate the flexibility of the proposed method using numerous coordinating metal ions (M = Cu, Mn, Ni, and Zr). The potential of these MOFs for electrochemical glucose sensing is examined using the hierarchical sheet-like Ni-BDC MOF as the optimum sample. It drives the electrocatalytic oxidation of glucose over a wide range (0.01 mM to 0.8 mM) with high sensitivity (635.9 µA mM-1 cm-2) in the absence of modification with carbon or the use of conductive substrates. It also demonstrates good selectivity with low limit of detection (LoD = 6.68 µM; signal/noise = 3), and fast response time (<5 s).

Organically Functionalized Mesoporous SBA-15 Type Material Bearing Fluorescent Sites for Selective Detection of HgII from Aqueous Medium.

Hg(II) contamination in water resources is one of the major health issues in keeping the purity standard of the municipal water supply. Herein, we report a new mesoporous sensor probe material SBA-ABZ-PEA having a 2D-hexagonally ordered mesoporous framework bearing covalently bonded fluorescent sites, and this has been synthesized through a two-step post-synthesis grafting route. A pure silica mesoporous SBA-15 material has been functionalized with (3-chloropropyl)triethoxysilane (ClPTES) to obtain chloro-functionalized SBA-15, which was further reacted with 4-aminobenzaldehyde followed by treatment with 2-(2-pyridyl)-ethylamine resulting in functionalized 2D-hexagonal mesoporous sensor probe SBA-ABZ-PEA. Small angle PXRD, N2 adsorption/desorption, HRTEM, TGA, and FT-IR studies have been carried out to characterize these materials. Our experimental results suggested successful grafting of the organic moiety on the SBA-15 surface along with preservation of mesoporosity throughout the grafting process. Photoluminescence measurements were carried out in the aqueous suspension of SBA-ABZ-PEA in the presence of different metal cations, like NaI, MgII, AlIII, KI, CaII, MnII, CoII, CuII, ZnII, CdII, PbII, and HgII. This result revealed that, among the various metal-ions, the emission intensity of the mesoporous sensing probe material SBA-ABZ-PEA has been dramatically quenched in the presence of the HgII ion. To check the sensitivity of the sensor probe, the fluorescence emission was also studied in the presence of different concentrations of HgII ions. A perfect linear plot between the concentrations of HgII ions in the aqueous medium with their corresponding fluorescence intensities with a detection limit of 1.2 × 10-6 M has been observed.

Recyclable Au/SiO2-Shell/Fe3O4-Core Catalyst for the Reduction of Nitro Aromatic Compounds in Aqueous Solution.

Highly stable gold nanoparticles immobilized on the surface of amine-functionalized nanocomposite microspheres possessing a magnetite (Fe3O4) nanoparticle core and a silica (SiO2) shell (Au/SiO2-shell/Fe3O4-core) were prepared. These gold nanocomposite catalysts were tested for 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) reduction in aqueous solution in the temperature range 293-323 K and in the presence of aqueous NaBH4 reducing agent. The magnetically recyclable gold catalyst showed high stability (∼3 months), efficient recyclability (up to 10 cycles), and high activity (∼100% conversion within 225 s, ∼700 ppm 4-NP or 2-NA). The pseudo-first-order apparent reaction rate constants (k) of 4-NP and 2-NA reduction were 7.5 × 10-3 and 4.1 × 10-3 s-1, respectively, and with an apparent catalytic activity of 4.48 × 10-8 kmol/(m3 s).

Ag nanoparticle-decorated, ordered mesoporous silica as an efficient electrocatalyst for alkaline water oxidation reaction.

In recent years, several novel strategies for speeding up the slow kinetics of the water oxidation reaction have attracted considerable attention for generation of O2. This is particularly important from the environmental perspective. Here we report a SBA-15 type, 2D-hexagonal functionalized mesoporous organosilica material as support for small Ag nanoparticles (NPs) by grafting the silica surface with 3-aminopropyltriethoxysilane, followed by chemical impregnation of Ag NPs at its surface, to obtain a AgNPs@SBA-NH2 material. The AgNPs@SBA-NH2 has been thoroughly characterized using several instrumental tools, such as powder X-ray diffraction, ultra-high resolution transition electron microscopy, N2 sorption, FT-IR spectroscopy, thermogravimetric and differential thermal analysis and X-ray photoelectron spectroscopy. High Brunauer-Emmett-Teller (BET) surface area and fine dispersion of Ag NPs throughout the surface of the amine-functionalized mesoporous material could enhance the rate of oxygen evolution reaction (OER) activity for AgNPs@SBA-NH2 in the electrochemical water splitting reaction.

MnAPO-5 as an efficient heterogeneous catalyst for selective liquid phase partial oxidation reactions.

Heterogeneous catalysts play a key role in addressing the economic and environmental issues of the chemical industry due to their several advantages, like ease of product separation, work-up and high recycling efficiency. Herein, we report the synthesis of a robust manganese(iv)-containing aluminophosphate material (MnAPO-5), with an AFI framework topology. This material has been characterized thoroughly by powder XRD, XPS, UHR TEM, FE SEM, 31P CP MAS NMR, atomic absorption spectroscopy, UV-visible spectroscopy and TGA. The Mn-containing microporous material has been employed as a heterogeneous catalyst for the oxidation of styrene and the synthesis of adipic acid from cyclohexanone in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant in air and it displayed very high recycling efficiency.

A new microporous oxyfluorinated titanium(IV) phosphate as an efficient heterogeneous catalyst for the selective oxidation of cyclohexanone.

Designing a new porous nanomaterial for eco-friendly catalytic reactions is very challenging. Here, a new crystalline microporous oxyfluorinated titanium phosphate material (TIPO-1) has been synthesized under hydrothermal conditions in the absence of any structure directing agent. The triclinic crystalline phase with the unit cell parameters a=7.962Å, b=10.006Å, c=13.979Å, α=96.921°, ß=95.851° and γ=93.760° has been indexed for TIPO-1 and it has been characterized through powder X-ray diffraction, nitrogen adsorption/desorption, XPS, FT-IR, 31P MAS NMR spectroscopy, UHR-TEM, FE-SEM and TGA/DTA analysis. The material exhibited excellent catalytic activity in liquid phase partial oxidation of cyclohexanone to adipic acid (up to 92% conversion) in the presence of aqueous H2O2 as oxidant together with value added side products like 1,6-hexandial and ε-caprolactone for reactions in different solvents. The material showed excellent recycling efficiency for six consecutive reaction cycles without any significant loss in catalytic activity.

A new strongly paramagnetic cerium-containing microporous MOF for CO2 fixation under ambient conditions.

Metal organic frameworks (MOFs) bearing multicarboxylate linkers are in great demand for designing robust heterogeneous catalysts. A new microporous Ce(iii)-based metal organic framework (Ce2NDC3) has been synthesized under solvothermal conditions, which showed strong paramagnetism and a CO2 uptake capacity of 1.64 mmol g-1 (7.23 weight%) at 273 K. The Ce2NDC3 showed high catalytic activity in CO2 fixation for the synthesis of cyclic carbonates with a maximum yield of 92% at ambient temperature and pressure. This rare earth metal-based MOF has been well characterized by single crystal X-ray diffraction, PXRD, N2 adsorption/desorption, UHR-TEM, FESEM, FTIR, 13C MAS NMR and TGA. Here, we have carried out magnetic analysis, which revealed that the Ce(iii) in this MOF exhibited 2F5/2 magnetism in the ground state. The Ce2NDC3 catalyst showed high recycling efficiency in CO2 fixation reactions, together with retention of the MOF structure after several rounds of reuse. Presumably, the presence of acidic Ce(iii) metal ions and microporosity in the coordinated polymer network is responsible for the high catalytic activity.