Effect of Amino and Carboxyl Functionalization on the Photoluminescence Properties of Rice Husk-Derived Carbon Quantum Dots (RH-CQDs)

In this work, carbon quantum dots (CQDs) are synthesized using rice husk as a natural precursor. The effect of amino and carboxyl functionalization is studied by adjusting the amount of ethylenediamine (EDA) as the amino source and ascorbic acid as the carboxyl source. HRTEM analysis show the formation of spherical carbon quantum dots. FTIR analysis confirms the presence of OH and CO bonding, indicating formation of CQDs. The addition of EDA and ascorbic acid quenches the fluorescence and shifts the emission wavelength from blue region (450-485 nm) to green region (500-565 nm). Based on the results, N-RHCQDs (0.6 ml) and C-RHCQDs (2.5ml) are chosen as the best samples as they give the highest quantum yield of 0.37% and 3.26% respectively. This implies that the fluorescence intensity is higher at a more basic and less acidic condition. This study suggests that the addition of different functionalization agents can tune the photoluminescence properties of CQDs that will be beneficial for its application.

Enhanced Electrochemical Characteristics of the Glucose Oxidase Bioelectrode Constructed by Carboxyl-Functionalized Mesoporous Carbon

This research revealed the effect of carboxyl-functionalization on the mesoporous carbon (MC)-fixed glucose oxidase (GOx) for promoting the properties of bioelectrodes. It showed that the oxidation time, temperature and concentration, can significantly affect MC carboxylation. The condition of 2 M ammonium persulfate, 50 °C and 24 h was applied in the study for the successful addition of carboxyl groups to MC, analyzed by FTIR. The nitrogen adsorption isotherms, and X-ray diffraction analysis showed that the carboxylation process slightly changed the physical properties of MC and that the specific surface area and pore size were all well-maintained in MC-COOH. Electrochemical characteristics analysis showed that Nafion/GOx/MC-COOH presented better electrocatalytic activity with greater peak current intensity (1.13-fold of oxidation peak current and 4.98-fold of reduction peak current) compared to Nafion/GOx/MC. Anodic charge-transfer coefficients (α) of GOx/MC-COOH increased to 0.77, implying the favored anodic reaction. Furthermore, the GOx immobilization and enzyme activity in MC-COOH increased 140.72% and 252.74%, leading to the enhanced electroactive GOx surface coverage of Nafion/GOx/MC-COOH electrode (22.92% higher, 1.29 × 10−8 mol cm−2) than the control electrode. Results showed that carboxyl functionalization could increase the amount and activity of immobilized GOx, thereby improving the electrode properties.

Influences of carboxyl functionalization of intercalators on exfoliation of graphite oxide: a molecular dynamics simulation

In this study, the influences of the carboxyl functionalization of intercalators on exfoliation of graphite oxide were analyzed using molecular dynamics (MD) simulations.