Phenyl-Modified Carbon Nitride Quantum Nanoflakes for Ultra-Highly Selective Sensing of Formic Acid: A Combined Experimental by QCM and Density Functional Theory Study.

Formic acid (HCOOH) is an important intermediate in chemical synthesis, pharmaceuticals, the food industry, and leather tanning and is considered to be an effective hydrogen storage molecule. Direct contact with its vapor and its inhalation lead to burns, nerve injury, and dermatosis. Thus, it is critical to establish efficient sensing materials and devices for the rapid detection of HCOOH. In the present study, we introduce a chemical sensor based on a quartz crystal microbalance (QCM) sensor capable of detecting trace amounts of HCOOH. This sensor is composed of colloidal phenyl-terminated carbon nitride (Ph-g-C3N4) quantum nanoflakes prepared using a facile solid-state method involving the supramolecular preorganization technology. In contrast to other synthetic methods of modified carbon nitride materials, this approach requires no hard templates, hazardous chemicals, or hydrothermal treatments. Comprehensive characterization and density functional theory (DFT) calculations revealed that the QCM sensor designed and prepared here exhibits enhanced detection sensitivity and selectivity for volatile HCOOH, which originates from chemical and hydrogen-bonding interactions between HCOOH and the surface of Ph-g-C3N4. According to DFT results, HCOOH is located close to the cavity of the Ph-g-C3N4 unit, with bonding to graphitic carbon and pyridinic nitrogen atoms of the nanoflake. The sensitivity of the Ph-g-C3N4-nanoflake-based QCM sensor was found to be the highest (128.99 Hz ppm-1) of the substances studied, with a limit of detection (LOD) of HCOOH down to a sub-ppm level of 80 ppb. This sensing technology based on phenyl-terminated attached-g-C3N4 nanoflakes establishes a simple, low-cost solution to improve the performance of QCM sensors for the effective discrimination of HCOOH, HCHO, and CH3COOH vapors using smart electronic noses.

Bispropylurea bridged polysilsesquioxane: A microporous MOF-like material for molecular recognition.

Microporous organosilicas assembled from polysilsesquioxane (POSS) building blocks are promising materials that are yet to be explored in-depth. Here, we investigate the processing and molecular structure of bispropylurea bridged POSS (POSS-urea), synthesised through the acidic condensation of 1,3-bis(3-(triethoxysilyl)propyl)urea (BTPU). Experimentally, we show that POSS-urea has excellent functionality for molecular recognition toward acetonitrile with an adsorption level of 74 mmol/g, which compares favourably to MOFs and zeolites, with applications in volatile organic compounds (VOC). The acetonitrile adsorption capacity was 132-fold higher relative to adsorption capacity for toluene, which shows the pores are highly selective towards acetonitrile adsorption due to their size and arrangement. Theoretically, our tight-binding density functional and molecular dynamics calculations demonstrated that this BTPU based POSS is microporous with an irregular placement of the pores. Structural studies confirm maximal pore sizes of ∼1 nm, with POSS cages possessing an approximate edge length of ∼3.16 Å.

Layer-by-Layer Motif Heteroarchitecturing of N,S-Codoped Reduced Graphene Oxide-Wrapped Ni/NiS Nanoparticles for the Electrochemical Oxidation of Water.

A new heterostructured material is synthesized with lamellar arrangements in nanoscale precision through an innovative synthetic approach. The self-assembled Ni-based cyano-bridged coordination polymer flakes (Ni-CP) and graphene oxide (GO) nanosheets with a layered morphology (Ni-CP/GO) are used as precursors for the synthesis of multicomponent hybrid materials. Annealing of Ni-CP/GO in nitrogen at 450 °C allows the formation of Ni3 C/rGO nanocomposites. Grinding Ni-CP/GO and thiourea and annealing under the same conditions produces N,S-codoped reduced GO-wrapped NiS2 flakes (NiS2 /NS-rGO). Interestingly, further heating up to 550 °C allows the phase transformation of NiS2 into NiS accompanied by the formation of a face-centered cubic (FCC-Ni) metal phase between NS-rGO layers (FCC-Ni-NiS/NS-rGO). Among all the materials, the resulting FCC-Ni-NiS/NS-rGO exhibits good electrocatalytic activity and stability toward the oxygen evolution reaction (OER) owing to the synergistic effect of multiphases, the well-designed alternating layered structures on the nanoscale with abundant active sites.