Studies on 1,8-naphthalimide derivative as a robust multi-responsive receptor for an array of low cost microanalytical techniques for selective prompt and on-site recognition of duplicitous fluoride in semi-aqueous medium

Waste to value transformation: Converting Carica papaya seeds into green fluorescent carbon dots for simultaneous selective detection and degradation of tetracycline hydrochloride in water

Rampant use of antibiotics has resulted in their seepage into groundwater and ultimately ending up in the food chain, causing antimicrobial resistance. To address this issue, it is imperative to not only quantitatively detect but eliminate them from water. An eco-friendly, one-step microwave-induced pyrolysis of waste papaya seeds (PS) with ethylenediamine (EDA) for just 5min gave green fluorescent nitrogen-doped carbon dots (PS-CDs), which are capable of detecting and photocatalytically degrading TC. The fluorescence properties of PS-CDs displayed that it has high sensitivity and selectivity towards sensing of TC with a detection limit as low as 120 nM. Also, the method gave satisfactory recovery results when extrapolated to determine TC in spiked milk, orange juice, tap water, and honey samples. On the other hand, PS-CDs alone potentially function as an efficient photocatalyst for the degradation of TC. PS-CDs' dual functionality provides an effectual method for the simultaneous detection and degradation of TC by a single nanoprobe.

The detection of multiple analytes by using visual colorimetric and fluorometric multimodal chemosensor based on the azo dye

In recent decades, researchers have conducted in-depth studies of the design and synthesis of colorimetric/fluorometric probes and the application of such probes to biological and practical samples. The multifunctional colorimetric and fluorescent azo benzene-based probe (4′-hydroxyl-2,4-diaminoazobenzene, MP) was designed to detect Al³⁺, Fe³⁺, Cu²⁺ and F¯. Based on the distinct redshift of the absorption band and a significant color change (yellow → purple), MP was utilized for both naked-eyed and quantitative detection of Al³⁺ and Fe³⁺ after formation of the 1:1 complex. Test paper coated with MP and used in conjunction with a cell phone was used for colorimetric detection of Al³⁺ and Fe³⁺ ions (20 μM–2.0 mM) in water samples through naked-eye and digital image colorimetry. The “MP-Fe³⁺” coordination shift that occurs in the presence of the competitive ligand F¯ was used in the colorimetric measurement of F¯ in toothpaste. In the presence of Cu²⁺ ion, the non-emissive MP has transformed into fluorescent benzotriazole product PMP (Φ = 0.53) through the bimolecular rate-limiting step, and the second-order rate constant k is calculated as 31 ± 2 M⁻¹ s⁻¹. MP exhibits a “turn-on” fluorescence response in the presence of Cu²⁺ that is greater than its response in the presence of competitive species such as Fe³⁺, Al³⁺, Co²⁺, Fe²⁺, Zn²⁺, Cd²⁺, Mg²⁺, Mn²⁺, Ni²⁺ and Ag⁺. MP was shown to have low toxicity to living HeLa cells and to present good imaging characteristics for tracking of Cu²⁺ in vivo.

Quick and hassle-free smartphone's RGB-based color to photocatalytic degradation rate assessment of malachite green dye in water by fluorescent Zr-N-S co-doped carbon dots

Sunlight active blue emissive zirconium, nitrogen, and sulfur co-doped carbon dots (Zr-N-S-CDs) have been synthesized by microwave-induced pyrolysis for achieving efficient photocatalytic degradation of pollutant malachite green dye (MG) in water. Surface morphology studies using high-resolution transmission electron microscopy confirmed the formation of spherical-shaped CDs with an absorbance peak at 350 nm and emission peak at 437 nm in UV-vis and fluorescence spectroscopy, respectively. Surface functional groups, elemental composition, and metal/non-metal co-doping were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. To understand the photocatalytic performance of Zr-N-S-CDs, various parameters, such as the source of energy, concentration of dye, catalyst dosage, and change in pH, were investigated. MG dye (20 ppm) at a pH 7 with 0.5 mg/mL of Zr-N-S-CDs could be photodegraded efficiently in 90 min under sunlight (99%) compared to dark and artificial light conditions. Moreover, real-time analysis of degradation rate could be conveniently calculated by integrating the colorimetric responses of MG dye with RGB values obtained by the "Color Picker" app of a smartphone. The degradation rate obtained using a smartphone (97.89%) was found to be in agreement with the UV-vis spectroscopy (99%), thus, providing a new, handy, and instrument-free route for speedy and quantitative estimation of the degradation of hazardous MG dye by Zr-N-S-CDs.

A Chemosensor of 1,8-Dihydroxyanthraquinone PMOs Prepared in a Ternary Deep Eutectic Solvent for the Sensitive Detection of Cu2

A novel type of organic-inorganic hybrid periodic mesoporous materials based on 1,8-dihydroxyanthraquinone (DHAQ-PMOs) was synthesized in a ternary deep eutectic solvent (DES). In the process of the material synthesis, an organosiloxane precursor (DHAQ-Si) and tetraethylorthosilicate (TEOS) were used as the mixed Si source, and cetyltrimethylammonium bromide (CTAB) was used as the structure directing agent. The DES formed by choline chloride (ChCl), urea (U), and ethylene glycol (EG) was used as a green solvent. The water needed for the hydrolysis of DHAQ-Si and TEOS was provided from free water in the sodium hydroxide solution. As characterized by small-angle X-ray scattering, nitrogen adsorption/desorption isotherms, and high-resolution transmission electron microscopy, the obtained mesoporous materials exhibit a two-dimensional hexagonal (P6mm) structure. DHAQ possesses double fluorescence emission peaks at ca. 520 and 580 nm due to the effect of the excited-state intramolecular proton transfer (ESIPT). For DHAQ-PMOs, the silica framework can provide a rigid environment that makes the fluorescence properties more stable and the fluorescence emission peak appears to red-shift obviously. The DHAQ-PMOs have high selectivity and sensitivity in a wide pH range that can be used to detect Cu²⁺, and the limit of detection (LOD) is as low as 2.39 × 10^-9 M. Fluorescence polarization experiments, high-resolution mass spectrometry, and Fourier transform infrared spectroscopy were used to study the coordination interaction between DHAQ and Cu²⁺. The density functional theory (DFT) was used to further prove the coordination ability and interaction between DHAQ and Cu²⁺. XPS spectra were also done to prove the coordination of DHAQ and DHAQ-PMO-10 with Cu²⁺. In addition, confocal fluorescence microscope images exhibit that DHAQ-PMOs can detect Cu²⁺ in living cells. The results show that DHAQ-PMOs have great application potential as a sensor for the detection of Cu²⁺.