Graphitic carbon nitride nanosheets as promising candidates for the detection of hazardous contaminants of environmental and biological concern in aqueous matrices

Ultrasensitive detection of Ag+and Ce3+ions using highly fluorescent carboxyl-functionalized carbon nitride nanoparticles

The fluorescence quenching of carboxyl-rich g-C3N4nanoparticles was found to be selective to Ag+and Ce3+with a limit of detection as low as 30 pM for Ag+ions. A solid-state thermal polycondensation reaction was used to produce g-C3N4nanoparticles with distinct green fluorescence and high water solubility. Dynamic light scattering indicated an average nanoparticle size of 95 nm. The photoluminescence absorption and emission maxima were centered at 405 nm and 540 nm respectively which resulted in a large Stokes shift. Among different metal ion species, the carboxyl-rich g-C3N4nanoparticles were selective to Ag+and Ce3+ions, as indicated by strong fluorescence quenching and a change in the fluorescence lifetime. The PL sensing of heavy metal ions followed modified Stern-Volmer kinetics, and CNNPs in the presence of Ag+/Ce3+resulted in a higher value ofKapp(8.9 × 104M-1) indicating a more efficient quenching process and stronger interaction between CNNP and mixed ions. Sensing was also demonstrated using commercial filter paper functionalized with g-C3N4nanoparticles, enabling practical on-site applications.

Sensing potential of C6N8 for ammonia (NH3) and nitrogen triflouride (NF3): A DFT study

The detection of toxic gases (NH3 and NF3) in regulating and monitoring air quality in the atmosphere has drawn a lot of attention. Herein, we explored a novel material (C6N8) for the detection of the important but toxic gases (NH3 and NF3). We investigated the interactions of the NH3 and NF3 with C6N8 through DFT at B3LYP, ωB97XD, and non-DFT M06-2X. Counterpoise interaction energy values (Eint. cp.) of NH3@C6N8 and NF3@C6N8 are -0.45 eV and -3.51 eV (for B3LYP), -0.42 eV and 2.11 eV (for ωB97XD) and -0.44 eV and -3.41eV (for M06-2X), respectively. Complexes having the most stable configurations were then subjected to further analyses including frontier molecular orbitals, H-L gap, and conductivity of complexes. An increase in the H-L gap in complexes (NH3@C6N8 and NF3@C6N8) is observed. The conductivity of NH3@C6N8 and NF3@C6N8 decreases as compared to C6N8. A considerable change in dipole moment was seen in C6N8 before and after complex formation. This is because of the shifting of charge between C6N8 and gases (NH3 and NF3). CHELPG and NBO charge analysis were used to evaluate the amount of charge transfer between C6N8 and gases. These analyses demonstrate that NH3 and NF3 withdraw electron density from C6N8. It was found that NH3 tends to be physically adsorbed on C6N8 while NF3 adsorbs chemically on C6N8. NCI and QTAIM analyses were performed to investigate the kind of interactions between the surface (C6N8) and gases (NH3 and NF3). Furthermore, the recovery time of NH3@C6N8 and NF3@C6N8 shows that C6N8 can be a better choice for sensing NH3 and NF3 gases.

Emerging Trends in nanostructured materials-coated screen printed electrodes for the electrochemical detection of hazardous heavy metals in environmental matrices

Heavy metal ions (HMIs) have become a significant contaminant in recent years. The increase in heavy metal pollution is a serious situation, requiring progressively robust, fast sensing, highly sensitive, and suitable techniques for heavy metal detection. Compared to other classical analytical methods, electroanalytical techniques, especially stripping voltammetric techniques with modified screen-printed electrodes (SPEs), have several advantages, such as fast sensing, great sensitivity, specificity, and long-time stability. Therefore, these techniques are more suitable for HMI detection. In this review, the nanostructured materials used to coat SPEs for the electrochemical determination of HMI are summarized. Additionally, the electrode fabrication method, modification steps, and electroanalytical study of these materials are systematically discussed. Hence, this review will support the researchers in precisely evaluating the electrochemical HMIs detection through highly sensitive stripping voltammetric techniques using SPE modified with nanostructured carbon and their allotropes, metal, metal oxides and their nanocomposites as sensor materials. Moreover, modified electrodes real time detection of HMIs in different food and environmental samples were briefly discussed.

Enzymatic reaction modulated DNA assembly on graphitic carbon nitride nanosheets for sensitive fluorescence detection of acetylcholinesterase activity and inhibition

A novel fluorescent strategy has been developed by using an enzymatic reaction modulated DNA assembly on graphitic carbon nitride nanosheets (CNNS) for the detection of acetylcholinesterase (AChE) activity and its inhibitors. The two-dimensional and ultrathin-layer CNNS-material was successfully synthesized through a chemical oxidation and ultrasound exfoliation method. Because of its excellent adsorption selectivity to ssDNA over dsDNA and superior quenching ability toward the fluorophore labels, CNNS were employed to construct a sensitive fluorescence sensing platform for the detection of AChE activity and inhibition. The detection was based on enzymatic reaction modulated DNA assembly on CNNS, which involved the specific AChE-catalyzed reaction-mediated DNA/Hg²⁺ conformational change and subsequent signal transduction and amplification via hybridization chain reaction (HCR). Under the excitation at 485 nm, the fluorescence signal from 500 to 650 nm (λ_max = 518 nm) of the developed sensing system was gradually increased with increasing concentration of AChE. The quantitative determination range of AChE is from 0.02 to 1 mU/mL and the detection limit was 0.006 mU/mL. The developed strategy was successfully applied to the assay of AChE in human serum samples, and can also be used to effectively screen AChE inhibitors, showing great promise providing a robust and effective platform for AChE-related diagnosis, drug screening, and therapy.