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Summary Large-scale inhomogeneous plasmonic metal chips have been demonstrated as a promising platform for biochemical sensing, but the origin of their strong fluorescence enhancements and average gap dependence is a challenging issue due to the complexity of modeling tremendous molecules within inhomogeneous gaps. To address this issue, we bridged microscopic mechanisms and macroscopic observations, developed a kinetic model, and experimentally investigated the fluorescence enhancement factors of IR800-streptavidin immobilized on metal nanoisland films (NIFs). Inspired by the kinetic model, we controlled the distribution of IR800-streptavidin within the valleys of NIFs by regioselective modification and achieved the fluorescence intensity enhancement up to 488-fold. The kinetic model allows us to qualitatively explain the mechanism of fluorescence intensity enhancements and quantitatively predict the trend of experimental enhancement factors, thereby determining the design principles of the plasmonic metal chips. Our study provides one key step further toward the sensing applications of large-scale plasmonic metal chips.

A clear and positive correlation between the CO2 concentration and the blood-sugar level has been observed via a noninvasive and time-dependent monitoring of CO2 concentration from human breath, which is carried out by using a homemade gas chromatography (GC)/milli-whistle compact analyzer. The time-dependent sampling of the CO2 concentration correlated between 5.0 to 5.6% (1% = 104 ppm) in accordance with blood-sugar level variations of 80 to 110 mg/dL. The analytical method results in a rapid, continuous and non-invasive determination of blood-sugar level via measurement of the CO2 concentration exhaled from the lungs.

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Photocatalytic water splitting is a promising way to produce hydrogen fuel from solar energy. In this regard, the search for new photocatalytic materials that can efficiently split water into hydrogen is essential. Here, using first-principles simulations, we demonstrate that the dual-defective SnS2 (Ni-SnS2-VS), by both single-atom nickel doping and sulfur monovacancies, becomes a promising two-dimensional photocatalyst compared with SnS2. The Ni-SnS2-VS monolayer, in particular, exhibits a suitable band alignment that perfectly overcomes the redox potentials for overall water splitting. The dual-defective monolayer displays remarkable photocatalytic activity, a spatially separated carrier, a broadened optical absorption spectrum, and enhanced adsorption energy of H2O. Therefore, the dual-defective SnS2 monolayer can serve as an efficient photocatalyst for overall water splitting to produce hydrogen fuel. Furthermore, a novel dual-defect method can be an effective strategy to enhance the photocatalytic behavior of 2D materials; it may pave inroads in the development of solar-fuel generation.

Exploring electrocatalysts composed of earth-abundant elements for a highly efficient hydrogen evolution reaction (HER) is scientifically and technologically important for electrocatalytic water splitting. In this work, we report HER properties of acid treated pyrolyzed vitamin B12 supported on reduced graphene oxide (B12/G800A) that shows an extraordinarily enhanced catalytic activity with low overpotential (115 mV vs. RHE at 10 mA cm−2), which is better than that of most traditional nonprecious metal catalysts in acidic media. Stability tests through long-term potential cycles and at a constant current density confirm the exceptional durability of the catalyst. Notably, the B12/G800A catalyst exhibits extremely high turnover frequencies per cobalt site in acid, for example, 0.85 and 11.46 s−1 at overpotentials of 100 and 200 mV, respectively, which are higher than those reported for other scalable non-precious metal HER catalysts. Moreover, it has been conjectured that the covalency of Co–C and Co–N bonds affects HER activities by comparing the extended X-ray absorption fine structure (EXAFS) spectra of the B12/G800A. High-temperature treatment can modify the Co-corrin structure of B12 to form Co–C bonds along with Co–N, which broadens the band of cobalt, essentially lowering the d-band center from its Fermi level. The lower d-band center leads to a moderate hydrogen binding energy, which is favorable for hydrogen adsorption and desorption.

Designing highly conducting metal–organic frameworks (MOFs) is currently a subject of great interest for their potential applications in diverse areas encompassing energy storage and generation. Herein, a strategic design in which a metal–sulfur plane is integrated within a MOF to achieve high electrical conductivity, is successfully demonstrated. The MOF {[Cu2(6-Hmna)(6-mn)]·NH4}n (1, 6-Hmna = 6-mercaptonicotinic acid, 6-mn = 6-mercaptonicotinate), consisting of a two dimensional (–Cu–S–)n plane, is synthesized from the reaction of Cu(NO3)2, and 6,6′-dithiodinicotinic acid via the in situ cleavage of an S–S bond under hydrothermal conditions. A single crystal of the MOF is found to have a low activation energy (6 meV), small bandgap (1.34 eV) and a highest electrical conductivity (10.96 S cm−1) among MOFs for single crystal measurements. This approach provides an ideal roadmap for producing highly conductive MOFs with great potential for applications in batteries, thermoelectric, supercapacitors and related areas.

Polybenzimidazoles containing heterocyclic benzo[c]cinnoline structure are synthesized from 3,8-benzo[c]cinnoline dicarboxylic acid, terephthalic acid and 3,3′-diaminobenzidine. Their membranes are prepared by sol-gel process, involving the conversion of polymer solution in polyphosphoric acid to phosphoric acid. The acid doping levels of the as-prepared membranes increase as the contents of benzo[c]cinnoline increase, indicating good interaction between phosphoric acid and benzo[c]cinnoline structure. The as-prepared membranes with high acid doping levels might lead to the dissolution of membranes in phosphoric acid at temperature higher than 120 °C. A new method is proposed to adjust acid doping levels by immersing the as-prepared membranes in diluted phosphoric acid solutions of various concentrations. The adjusted membranes (acid doping levels around 30 PA RU−1) exhibit enhanced mechanical properties with tensile strength in the range of 4.1–5.2 MPa. The proton conductivity of adjusted membranes maintain at 0.15–0.17 S cm−1 at 160 °C under ambient atmosphere without humidification. The single cells based on the adjusted membranes exhibit open circuit voltages and peak power densities from 0.89 to 0.91 V and 691–1253 mW cm−2 at 160 °C, respectively. Compared to other polybenzimidazole membranes prepared by sol-gel process, the adjusted polybenzimidazoles show higher mechanical strength and better single cell performance.