Sensitive and selective fluorometric determination of DNA by using layered hexagonal nanosheets of a covalent organic framework prepared from p-phenylenediamine and benzene-1,3,5-tricarboxaldehyde

A modified method is described for the preparation of amino-functionalized covalent organic framework nanosheets (COF-NSs). These consist of hexagonal layered sheets and were prepared from commercially available starting materials (p-phenylenediamine and benzene-1,3,5-tricarboxaldehyde). The interlayer stacking interactions between the ultra-thin COF-NSs became weak because the pi stacking is destroyed by sonication. This result in the exfoliation of COF-NSs. As an application, the COF-NSs used for sensitive and selective fluorometric determination of DNA. To reach this goal, H1 and H2 hairpin-like DNA probes were chosen; H1 used Texas Red-labeled dye as a fluorescent probe. The addition of the COF-NSs, the hairpin probes was adsorbed onto the porous surface of the COFNSs. The pi stacking and hydrogen-bond interactions between COFNSs and nucleic acid quench the fluorescence of the Texas red-labeled probe. The target DNA enables the recovery of the quenched fluorescence of the Texas red-labelled probe by triggering an inter-chain hybridization within hairpin probes. This results in a weaker interaction of double-stranded DNA (dsDNA) with the COFNSs. Consequently, the dsDNA detaches from the COFNSs, thereby recovering the dye's fluorescence (excitation/emission maxima at 590/612 nm) with increasing target DNA concentration. The findings were applied to design a method for the determination of DNA that has a 2 pM detection limit. This is significantly lower than the limit of detection reported previously for 2D nanomaterial-based fluorometric DNA assays

Adsorption of Pb²⁺ Ions from Aqueous Solution onto Porous Kappa-Carrageenan/Cellulose Hydrogels: Isotherm and Kinetics Study

Heavy metal ion pollution poses severe health risks. In this study, a kappa-carrageenan/cellulose (κ-CG/CL) hydrogel was prepared using a facile one-step method to remove Pb2+ ions from aqueous solutions. The functional groups and crystallinity nature of κ-CG/CL hydrogel have been identified via Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). In contrast, the porous morphology and size distribution on the surface of κ-CG/CL hydrogel with a pore size of 1–10 μm were identified using scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET) surface area analysis. The as-prepared κ-CG/CL hydrogel effectively removed Pb2+ ions, primary environmental pollutants. The effects of pH and contact time on Pb2+ adsorption were studied along with the adsorption isotherms and kinetics of Pb2+ adsorption onto the hydrogels from aqueous solutions. Notably, the aqueous solutions were effectively treated with the prepared κ-CG/CL hydrogels to remove Pb2+ ions. The adsorption results fit well with pseudo-first- and second-order kinetic, Elovich, intra-particle diffusion, and Langmuir and Freundlich isotherm models. Based on the fitting results, the maximum adsorption capacity was obtained with the Freundlich isotherm model of κ-CG/CL hydrogel found to be 486 ± 28.5 mg/g (79%). Reusability studies revealed that the κ-CG/CL hydrogel could remove Pb2+ ions with more than 79% removal efficiency after eight adsorption–desorption cycles. In addition, its mechanism for efficiently adsorbing and removal of Pb2+ ions was analyzed. These findings imply that the κ-CG/CL hydrogel has substantial potential for application in removing and recycling heavy metal ions from aqueous solutions

Ruthenium(ii)-catalyzed regioselective direct C4-and C5-diamidation of indoles and mechanistic studies

A ruthenium(ii)-catalyzed regioselective direct diamidation of 3-carbonylindoles at the C4- and C5-positions using various dioxazolones is described. This novel protocol allows for the effective installation of two amide groups on the benzene ring in indole. A remarkably broad substrate scope, excellent functional group tolerance, and mild reaction conditions are notable features of this protocol. Further explorations reveal that benzo[b]thiophene-3-carboxaldehyde is a viable substrate and affords its corresponding diamidation products. The diamido indoles are further converted into various functionalized products and used as sensors for metal ion detection. Density functional theory studies are also conducted to propose a reaction mechanism and provide a detailed understanding of the regioselectivity observed in the reaction.11Nsciescopu

Synthesis of Photoluminescent Carbon Dots Using <i>Hibiscus</i> Tea Waste and Heteroatom Doping for Multi-Metal Ion Sensing: Applications in Cell imaging and Environmental Samples

Novel photoluminescent carbon dots (CDs) were synthesized through a facile hydrothermal method using Hibiscus tea extract as a natural carbon source and boric acid as a boron source. The optical and physicochemical properties of the as-synthesized nitrogen- and boron-doped CDs (NB-CDs) were characterized using UV–Visible (UV–Vis), photoluminescence (PL) spectroscopy, Fourier-transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The as-synthesized NB-CDs showed spherical morphology of approximately 6.2 ± 0.5 nm with quantum yield (9.2%), high aqueous solubility, strong photo-stability, and excitation-dependent PL behavior. The obtained NB-CDs exhibited high stability over a wide pH range and high ionic strength. Additionally, NB-CDs exhibited PL enhancement response with excellent sensitivity toward multi-metal ions, including Ag+, Cd2+, and Cr3+ ions, with very low detection limits of 44.5, 164.4, and 54.6 nM, respectively, with a wide concentration range of 0–10 μM. Upon testing the cytotoxicity of the NB-CDs at a concentration of 20 μg/mL for 24 h, we found no obvious inhibition of cell viability. Therefore, the proposed sensor method can be successfully applied to detect Ag+, Cd2+, and Cr3+ ions in cell imaging as well as in real water environmental samples

Ti₃C₂-MXene/NiO Nanocomposites-Decorated CsPbI₃ Perovskite Active Materials under UV-Light Irradiation for the Enhancement of Crystal-Violet Dye Photodegradation

Ti3C2-MXene material, known for its strong electronic conductivity and optical properties, has emerged as a promising alternative to noble metals as a cocatalyst for the development of efficient photocatalysts used in environmental cleanup. In this study, we investigated the photodegradation of crystal-violet (CV) dye when exposed to UV light using a newly developed photocatalyst known as Ti3C2-MXene/NiO nanocomposite-decorated CsPbI3 perovskite, which was synthesized through a hydrothermal method. Our research investigation into the structural, morphological, and optical characteristics of the Ti3C2-MXene/NiO/CsPbI3 composite using techniques such as FTIR, XRD, TEM, SEM–EDS mapping, XPS, UV–Vis, and PL spectroscopy. The photocatalytic efficacy of the Ti3C2-MXene/NiO/CsPbI3 composite was assessed by evaluating its ability to degrade CV dye in an aqueous solution under UV-light irradiation. Remarkably, the Ti3C2-MXene/NiO/CsPbI3 composite displayed a significant improvement in both the degradation rate and stability of CV dye when compared to the Ti3C2-MXene/NiO nanocomposite and CsPbI3 perovskite materials. Furthermore, the UV–visible absorption spectrum of the Ti3C2-MXene/NiO/CsPbI3 composite demonstrated a reduced band gap of 2.41 eV, which is lower than that of Ti3C2-MXene/NiO (3.10 eV) and Ti3C2-MXene (1.60 eV). In practical terms, the Ti3C2-MXene/NiO/CsPbI3 composite achieved an impressive 92.8% degradation of CV dye within 90 min of UV light exposure. We also confirmed the significant role of photogenerated holes and radicals in the CV dye removal process through radical scavenger trapping experiments. Based on our findings, we proposed a plausible photocatalytic mechanism for the Ti3C2-MXene/NiO/CsPbI3 composite. This research may open up new avenues for the development of cost-effective and high-performance MXene-based perovskite photocatalysts, utilizing abundant and sustainable materials for environmental remediation

The surfactants mediated electropolymerized poly(aniline) (PANI)-reduced graphene oxide (rGO) composite counter electrode for dye-sensitized solar cell

In this work, poly(aniline) (PANI)-reduced graphene Oxide (rGO) low-cost nanocomposite used for counter electrode (CE) in dye-sensitized solar cells (DSSCs) for the replacement of the high-cost platinum (Pt) CE. The nanocomposite CEs were prepared with three different types of structural determine agents (cationic, non-ionic and anionic namely CTAB, Triton-X100, SDS) in aqueous medium and characterized by HR-SEM &amp; TEM, XRD pattern analysis, FT-IR and Raman spectral studies. Electrochemical impedance spectroscopy (EIS) studies were used to determine the PANI-rGO-anionic surfactant in lower charge transfer resistance compared with, PANI, rGO and other type surfactants used in the preparation of CEs. DSSC assembled with a N719 dye sensitized TiO2 photo-anode, Poly(ethylene oxide) (PEO), iodide/triiodide redox couple containing electrolyte and PANI-rGO-anionic surfactant CE showed a sunlight-into-electrical energy conversion efficiency of 7.60%, which is higher than that of DSSC fabricated with pure Pt (6.40%), PANI (4.81%), rGO (4.30%) and PANI-rGO-CTAB (6.26%) and PANI-rGO-Triton X 100 (5.72%)