1D Covalent Organic Frameworks Triggering Highly Efficient Photosynthesis of H2 O2 via Controllable Modular Design.

The topological diversity of covalent organic frameworks (COFs) enables considerable space for exploring their structure-performance relationships. In this study, we report a sequence of novel 1D COFs (EO, ES, and ESe-COF) with typical 4-c sql topology that can be interconnected with VIA group elements (O, S, and Se) via a modular design strategy. It is found that the electronic structures, charge delivery property, light harvesting ability, and hydrophilicity of these 1D COFs can be profoundly influenced by the bridge-linked atom ordinal. Finally, EO-COF, possessing the highest quantity of active sites, the longest lifetime of the active electron, the strongest interaction with O2 , and the lowest energy barrier of O2 reduction, exhibits exceptional photocatalytic O2 -to-H2 O2 activity under visible light, with a production rate of 2675 µmol g-1 h-1 and a high apparent quantum yield of 6.57 % at 450 nm. This is the first systematic report on 1D COFs for H2 O2 photosynthesis, which enriches the topological database in reticular chemistry and promotes the exploration of structure-catalysis correlation.

Mixed-Blocks-Driving Nickel-Porphyrin Covalent Organic Polymers for Photocatalytic Syngas Production from CO2 with Fine Selectivity.

CO2 photoconversion to syngas with superb selectivity is a splendid and bright option to achieve environmental improvement, energy substitution, and industrial needs. Herein, a series of Ni-porphyrin covalent organic polymers (COPs) interspersed with furan and thiophene using a mixed-blocks-engineering strategy, named as OXSY-Ni COPs (X and Y refer to the relative amounts of furan and thiophene blocks, respectively), are synthesized for photocatalytic CO2-to-syngas. Ni-coordinated porphyrin cores prefer to act as mediators of CO2-to-CO photoconversion because of the higher adsorption capacity of CO2. Ni-free porphyrins work mainly as active sites of H2 photoevolution. Furthermore, introducing different amounts of furan and thiophene modulates jointly the electronic structure of Ni-porphyrin COPs and optimizes the conduction band alignment. The above controllable variables achieve a wonderful syngas (CO/H2) ratio range from 2:1.06 to 1:1.04 for the Fischer-Tropsch process within common industrial reactions. Notably, the COP of the O1S3-Ni COPs exhibits excellent photocatalytic CO2-to-syngas activity under visible light, with a syngas yield of 8442.5 µmol g-1 h-1 (CO/H2 = 1:1.02) and an apparent quantum efficiency (AQE) of 1.92% at 450 nm. This strategy would provide a significance path to design functional and efficient organic semiconductors.

SARS-CoV-2 proteins monitored by long-range surface plasmon field-enhanced Raman scattering with hybrid bowtie nanoaperture arrays and nanocavities.

The identification of biomacromolecules by using surface-enhanced Raman scattering (SERS) remains a challenge because of the near-field effect of traditional substrates. Long-range surface plasmon resonance (LRSPR) is a special type of surface optical phenomenon that provides higher electromagnetic field enhancement and longer penetration depth than conventional surface plasmon resonance. To break the limit of SERS detection distance and obtain a SERS substrate with increased enhancement ability, a bowtie nanoaperture array was sandwiched between two symmetric dielectric environments. Then, an Au mirror was inserted to form a metal-insulator-metal configuration. Finite-difference time-domain simulations revealed that numerous hybrid modes can be provided by this novel configuration (denoted as long-range SERS [LR-SERS] substrate). In particular, the LRSPR mode can be excited and reach the maximum value through the regulation of the polarizations of the incident light and the geometrical parameters of the LR-SERS substrate. The optimized LR-SERS substrate was then applied to detect SARS-CoV-2 spike (S) and nucleocapsid (N) proteins. This substrate displayed ultralow detection limits of ∼9.2 and ∼11.3 pg mL-1 for the S and N proteins, respectively. Moreover, with the help of principal component analysis and receiver operating characteristic methods, our fabricated sensors exhibited excellent selectivity and hold great potential for the diagnosis of SARS-CoV-2 proteins in real samples.

In Situ Surface-Enhanced Raman Scattering Detection of a SARS-CoV-2 Biomarker Using Flexible and Transparent Polydimethylsiloxane Films with Embedded Au Nanoplates.

Coronavirus disease 2019 (COVID-19) remains an ongoing issue worldwide and continues to disrupt daily life. Transmission of infection primarily occurs through secretions when in contact with infected individuals, but more recent evidence has shown that fomites are also a source of virus transmission, especially in cold-chain logistics. Traditional nucleic acid testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contamination in cold-chain logistics is time-consuming and inaccurate because of the multiplex sampling sites. Surface-enhanced Raman spectroscopy (SERS) provides a rapid, sensitive, and label-free detection route for various molecules, including viruses, through the identification of the characteristic peaks of their outer membrane proteins. In this study, we embedded arbitrarily orientated gold nanoplates (Au NPLs) in polydimethylsiloxane (PDMS) elastomer and used it as biosensor for the ultrasensitive detection of the SARS-CoV-2 spike protein in cold-chain logistics. This transparent and flexible substrate can be wrapped onto arbitrary surfaces and permits light penetration into the underlying contact surface, enabling in situ and point-of-care SERS diagnostics. The developed assay displayed high reproducibility (8.7%) and a low detection limit of 6.8 × 10-9 g mL-1, indicating its potential to serve as a promising approach with increased accuracy and sensitivity for the detection of the S protein.

NaOH-induced formation of 3D flower-sphere BiOBr/Bi4O5Br2 with proper-oxygen vacancies via in-situ self-template phase transformation method for antibiotic photodegradation.

In this study, a novel 3D flower-sphere BiOBr/Bi4O5Br2 with proper-oxygen vacancies (OV) was successfully synthesized by using 3D BiOBr as a self-sacrificed template, NaOH as a structure-driving reagent and midwifery agent of OV. The synthesis mechanism was systematically studied. It revealed that Bi4O5Br2 lamina generated via in-situ phase transfer tightly interspersed in the interior and surface of 3D BiOBr hierarchical structures; calcination temperature, stirring time and -OH concentration can optimize the composition and structure of materials. Also, the calcination conditions (temperatures and air or N2 atmosphere) can regulate the OV's concentration. Ultimately, 3D hierarchical architectures, the optimal heterojunction composition and OV with proper concentrations three positive factors synergistically promoted the photoelectric activity of BiOBr/Bi4O5Br2-OV, making it exhibit ultrahigh photocatalytic activity for antibiotic photodegradation (tetracycline, TC; ciprofloxacin, CIP). We believe the synthesis methods and design idea mentioned in this paper have high instructive significance to prepare high-performance materials.

[Ammonium Adsorption Characteristics in Aqueous Solution by Titanate Nanotubes].

Titanate nanotubes (TNTs) were synthesized via a hydrothermal method using P25 and NaOH as the raw materials. The composition and morphology of the nanotubes were characterized by X-ray diffraction and transmission electron microscopy. The adsorption characteristics and the rules of ammonium in aqueous solutions were tested in the static system. The results showed that when the alkali concentration was 10 mol·L-1, titanate nanotubes with a length of approximately 120 nm and a diameter of approximately 8 nm were obtained. The equilibrium adsorption capacity of ammonium was 10.67 mg·g-1. When the pH ranged between 3 and 8, TNTs effectively adsorbed ammonium. The equilibrium adsorption time was 1 h, and this followed the pseudo second-order model. The results from the intra-particle model also showed that the adsorption process of ammonium by TNTs was controlled by surface adsorption and inter-particle diffusion. The Temkin model gave the best fit for the adsorption of ammonium onto TNTs. The thermodynamic experiments showed that the adsorption of titanate nanotubes on ammonium was a spontaneous endothermic process. Coexisting anions and cations had an inhibitory effect on the adsorption of ammonium. The order of influence was SO42- > Cl- > H2PO4- and K+ > Na+ > Ca2+, respectively. The adsorption effect of ammonium by regenerated TNTs remained more than 88.64% after five repeat usages. The results of Fourier transform infrared spectroscopy showed that the ammonium adsorption mechanism of titanate nanotubes was ion-exchange between NH4+ and Na+ in the TNTs. Titanate nanotubes can effectively remove ammonium from water because of their good recycling capacity and large adsorption capacity.

Preparation and Characterization of Bi2Ti2O7 Pyrochlore by Acetone Solvothermal Method.

In this study, we reported a novel synthesis route of Bi2Ti2O7 pyrochlore by acetone solvothermal method. The bismuth nitrate and tetrabutyl titanate were used as reactant, and acetone was used as solvent. XRD patterns showed that the pure Bi2Ti2O7 particles were synthesized when the molar ratio of Bi/Ti was between 0.4 and 0.8. The SEM showed that the Bi2Ti2O7 crystal was uniform spherical particles. The carboxylic acid produced in the reaction system may be the main factor of bismuth mineralization. Compared with TiO2, pure Bi2Ti2O7 photocatalyst exhibited superior photocatalytic activity for methyl orange (MO) and tetracycline hydrochloride (TC) under simulated solar light. The possible formation mechanism was proposed.