Copper Indium Sulphide-based quantum dots (CIS QDs) are cadmium-free materials owing to their tunable optical properties with potential for biomedical applications. In this work, CIS/ZnS nanoparticles (NPs) are synthesized by hydrothermal synthesis of CIS QDs, followed by the growth of ZnS shell, and further functionalized by RGD-peptide to study the effect of shell formation, peptide functionalization, and their pH-dependent optical response. The effect of pH and peptide functionalization on the optical properties of CIS/ZnS core/shell NPs has remained largely unexplored. Detailed characterizations were carried out using HRTEM, FT-IR, UV-Vis, PL, DLS, and zeta potential measurements. HRTEM micrographs revealed near-spherical NPs with size distributions indicative of morphological changes as a result of shell formation and peptide functionalization, while FT-IR data showed RGD-peptide related amide bands in the functionalized NPs, providing supportive evidence for possible amide-coupling process. The PL intensity measurements indicated an increased emission after the growth of a ZnS shell. The calculated relative PL QY compared to Rhodamine 6G as a standard were 18.3
Herein, we investigated the local organization, fluorescence dynamics, and dynamic heterogeneity in low transition temperature mixtures (LTTMs) composed of 1-butyl-3-methylimidazolium chloride (BmimCl; Tm = 343 K), 1-ethyl-3-methylimidazolium chloride (EmimCl; Tm = 353 K), and acetamide (ACM; Tm = 352 K) using steady-state and time-resolved fluorescence spectroscopy. Both mixtures exhibit pronounced excitation-wavelength-dependent emission behavior, with an overall shift of 170 nm in the emission maxima, suggesting the presence of various local molecular environments within the mixtures. Fluorescence lifetime analyses reveal three decay components ( 300 ps, 1.7–1.9 ns, and 5.5–5.9 ns), indicating tri-exponential fluorescence decay with contributions occurring over different timescales. Time-resolved fluorescence anisotropy studies at different excitation wavelengths at 298 K yield rotational relaxation times ( τ _r ) of 18.34–20.65 ns and 12.69–16.55 ns for BmimCl-ACM and EmimCl-ACM, respectively. Furthermore, the temperature-dependent reorientational dynamics exhibit a fractional viscosity dependence, with exponents of 0.47 for BmimCl-ACM and 0.85 for EmimCl-ACM, confirming the presence of dynamic heterogeneity in these LTTMs, with the former system displaying a greater extent of heterogeneity. Complementary 2D 11H-1H NOESY experiments reveal stronger cross-peaks for BmimCl-ACM, suggesting closer spatial association between the components compared with the EmimCl-ACM system. Overall, the combined optical spectroscopy and NMR results demonstrate that BmimCl-ACM forms a more strongly associated molecular structure compared to the EmimCl-ACM system. These findings underline how subtle variations in imidazolium cation structure govern molecular organization and dynamics in LTTMs, providing useful guidelines for the rational design of environmentally benign solvent systems.
The increasing prevalence of salicylic acid as an unauthorized adulterant in milk and its derived products poses serious concerns for human health and safety. In this study, a fluorescent probe based on boron-doped carbon dot-integrated poly(N-isopropylacrylamide) microgels (BCQDs@PNIPAM) was developed for the selective and sensitive detection of salicylic acid. The incorporation of carbon quantum dots (CQDs) within the PNIPAM microgel matrix not only imparts strong fluorescence but also minimizes their inherent tendency to self-aggregate, thereby enabling a stimuli-responsive sensing platform for salicylic acid detection. The biocompatibility of the developed probe was further evaluated through seed germination and bacterial assays. Moreover, the introduction of electron-deficient boron into the CQDs enhances their fluorescence performance, improving selectivity and quick response with “turn-on” signal for salicylic acid. Using this strategy, the probe demonstrated a linear detection range of 1-240 µM with a low limit of detection (LOD) of 54 nM. The feasibility of the sensing platform was demonstrated in real samples, highlighting its potential in quality control in food products. In addition, the enhanced fluorescence characteristics of the hybrid microgels enabled their application in security and anti-counterfeiting systems. Overall, this work offers a reliable and sustainable sensing platform for ensuring milk quality and safety, with promising implications for food surveillance and public health protection.
This study investigates the hydrogen storage capabilities of MXene-based nanoclusters (Hf2C, Ta2C, and W2C) using first-principles density functional theory calculations. All nanoclusters exhibit outstanding structural stability, reflected by strong binding energies (- 6.54 to - 7.38 eV) and the absence of vibrational instabilities. Electronic structure analysis identifies transition-metal sites with moderate positive electrostatic potentials as the most favorable centers for hydrogen adsorption. With increasing hydrogen loading, the adsorption mechanism evolves from chemisorption to a synergistic chemisorption-physisorption process. Non-covalent interaction analysis further confirms that progressive hydrogenation in M2C-nH(2) complexes (M = Hf, Ta, W) strengthens both attractive hydrogen-bond-like interactions and van der Waals forces. Notably, Ta2C and W2C nanoclusters achieve exceptional storage capacities (similar to 6.41 wt%), surpassing the DOE targets, while maintaining optimal adsorption energies ( similar to - 0.24 to - 0.28 eV/H-2) and practical desorption temperatures (222-364 K). These results position Ta2C and W2C MXene nanoclusters as highly promising materials for reversible hydrogen storage, offering a compelling balance of high capacity and favorable thermodynamic performance.
Kanamycin (KANA) is a veterinary drug residue that is highly scrutinized in food safety testing. In this study, a metal-organic framework-based aptamer-nanoenzyme (NH2-MIL-88B(Fe)/CDs-Apt) was introduced for the dual-mode detection of KANA. NH2-MIL-88B(Fe) catalyzes the oxidation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) by H2O2 to form blue ox-TMB, thereby enabling colorimetric detection. As a fluorescence quencher, NH2-MIL-88B(Fe) quenches the fluorescence of CDs via photogenerated electron transfer (PET) or fluorescence resonance energy transfer (FRET) mechanisms. The detection limits were 0.716 fM (fluorescent) and 0.709 fM (colorimetric), respectively. The proposed aptasensor was successfully applied to the detection of KANA in eggs, honey, and lake water. This aptasensor demonstrates high sensitivity and accuracy, as well as broad application potential.
