Structure modulation of g-C3N4 in TiO2{001}/g-C3N4 hetero-structures for boosting photocatalytic hydrogen evolution

Highly selective fluorescence detection of L-selenium-methylselenocysteine in selenium-enriched Cardamine violifolia

A feasible and practicable "off-on" type of fluorescence strategy for highly selective screening of L-selenium-methylselenocysteine (L-SeMC) in selenium-enriched Cardamine violifolia was developed using g-C3N4-MnO2 nanocomposites as fluorescent probes. The g-C3N4 nanosheets can emit blue fluorescence at 320 nm excitation wavelength with a fluorescence quantum yield of 28%. When MnO2 was deposited onto g-C3N4 nanosheets, the fluorescence of the g-C3N4 nanosheets was quenched due to fluorescence resonance energy transfer (FRET). After the addition of L-SeMC, MnO2 was reduced to Mn2+, which eliminated FRET and fluorescence was restored. Based on this, a quantitative method for the determination of L-SeMC was established. The fluorescence intensity of g-C3N4-MnO2 nanocomposites showed a good linear relationship with the concentration of L-SeMC in the range of 0-45 μg mL-1, the limit of detection (LOD, 3σ/K) was 8.25 ng mL-1 and the correlation coefficient was 0.9904. Common selenium compounds such as SeO2, Na2SeO3, SeMet and SeCys caused weak fluorescence intensity, which means that the developed method is highly selective to detect L-SeMC in a series of selenium compounds. Meanwhile, the technique was evaluated by spiking L-SeMC standards in C. violifolia extraction solutions and with 9 C. violifolia extraction specimens, receiving excellent accordance with results from the commercially available atomic fluorescence spectroscopy method.

g-C3N4@TiO2 photoanodes for high-efficiency QDSSCs: improved electron transfer and photochemical stability

In QDSSCs, a photoanode is an important part of connecting the external circuit, providing support for the transmission of photogenerated carriers to the external circuit, and also providing an attachment site for QDs. In this study, we prepared a g-C3N4@TiO2 composite for the photoanode by a two-step process. The results show that the use of g-C3N4@TiO2 greatly increases the specific surface area of the material, effectively inhibits the "electron-hole" recombination, and optimizes the stability and catalytic performance of the photoanode. Among them, the cell equipped with the g-C3N4@TiO2 photoanode has improved performance: Jsc = 26.5 mA cm-2, PCE = 8.2%, Voc = 0.62 eV, and FF = 0.50. Based on the research in this paper, it can be seen that the g-C3N4@TiO2 composite applied to the photoanode can effectively improve the cell performance and provide a feasible idea for optimizing QDSSCs.

Significantly enhanced photothermal catalytic CO2 reduction over TiO2/g-C3N4 composite with full spectrum solar light

Using solar energy to drive catalytic conversion of CO₂ into value-added chemicals has great potential to alleviate the global energy shortage and anthropogenic climate change. Herein, a "hitting three birds with one stone" strategy was reported to prepared boron-doped g-C₃N₄/TiO_2-x composite (BCT) by a one-step thermal reduction process. A series of characterizations showed that the composite catalyst has extended full-spectrum absorption, rapid photogenerated charge separation, and outstanding CO₂ photoreduction performance (265.2 μmol g^-1h^-1), which is 7.5 and 9.2 times higher than that of pure TiO₂ and g-C₃N₄, respectively. In addition, the CO₂ conversion rate can be further increased to 345.1 μmol g^-1h^-1 at 70 °C due to its excellent photothermal conversion. Mechanistic studies reveal that synergistic effects alter the charge density distribution, thereby lowering the energy barrier for CO₂ conversion by adsorbing and activating CO₂ molecules_. This work provides a novel three-in-one integrated strategy for fabricating high-efficiency catalysts.