Letteratura scientifica selezionata sul tema "I-II-III-VI QDs"

Highly efficient NIR-II luminescent nanoprobes of AgInTe2:Zn/ZnS QDs were successfully synthesized with the maximum quantum yield of 25.2%, and were employed for sensitive biodetection of xanthine oxidase with the limit of detection down to 25 nU L−1.

Effectively reducing the concentration of nitrogen-containing compounds (NCCs) remains a significant but challenging task in environmental restoration. In this work, a novel step-scheme (S-scheme) SnO2@MCr heterojunction was successfully fabricated via a facile hydrothermal method. At this heterojunction, MIL-101(Cr) octahedrons are decorated with highly dispersed SnO2 quantum dots (QDs, approximate size 3 nm). The QDs are evenly wrapped around the MIL-101(Cr), forming an intriguing zero-dimensional/three-dimensional (0D/3D) S-scheme heterostructure. Under simulated sunlight irradiation (280 nm < λ < 980 nm), SnO2@MCr demonstrated superior photoactivity toward the denitrification of pyridine, a typical NCC. The adsorption capacity and adsorption site of SnO2@MCr were also investigated. Tests using 20%SnO2@MCr exhibited much higher activity than that of pure SnO2 and MIL-101(Cr); the reduction ratio of Cr(VI) is rapidly increased to 95% after sunlight irradiation for 4 h. The improvement in the photocatalytic activity is attributed to (i) the high dispersion of SnO2 QDs, (ii) the binding of the rich adsorption sites with pyridine molecules, and (iii) the formation of the S-scheme heterojunction between SnO2 and MIL-101(Cr). Finally, the photocatalytic mechanism of pyridine was elucidated, and the possible intermediate products and degradation pathways were discussed.

Quantum indistinguishability plays a crucial role in many low-energy physical phenomena, from quantum fluids to molecular spectroscopy. It is, however, typically ignored in most high-temperature processes, particularly for ionic coordinates, implicitly assumed to be distinguishable, incoherent, and thus well approximated classically. We explore enzymatic chemical reactions involving small symmetric molecules and argue that in many situations a full quantum treatment of collective nuclear degrees of freedom is essential. Supported by several physical arguments, we conjecture a “quantum dynamical selection” (QDS) rule for small symmetric molecules that precludes chemical processes that involve direct transitions from orbitally nonsymmetric molecular states. As we propose and discuss, the implications of the QDS rule include (i) a differential chemical reactivity of para- and orthohydrogen, (ii) a mechanism for inducing intermolecular quantum entanglement of nuclear spins, (iii) a mass-independent isotope fractionation mechanism, (iv) an explanation of the enhanced chemical activity of “reactive oxygen species”, (v) illuminating the importance of ortho-water molecules in modulating the quantum dynamics of liquid water, and (vi) providing the critical quantum-to-biochemical linkage in the nuclear spin model of the (putative) quantum brain, among others.

Excessive N fertilizer use in agriculture results in the release of inorganic N contaminants into surface and groundwater bodies, and other negative environmental effects. The combined application of N fertilizers with charcoal and sago bark ash could help reduce these negative impacts. The objective of this sorption study was to examine the effects of the co-application of charcoal and sago bark ash with ammonium chloride in regulating the adsorption and release of NH4+ in an acid soil. This soil used in the laboratory study was Bekenu series (Typic Paleudults). The treatments evaluated were: (i) 300 g soil only, (ii) 300 g charcoal only, (iii) 300 g sago bark ash only, (iv) 300 g soil + 15.42 g charcoal, (v) 300 g soil + 7.71 g sago bark ash, and (vi) 300 g soil + 15.42 g charcoal + 7.71 g sago bark ash. Regardless of the concentration of the isonormal solution, sago bark ash (T3) showed the highest NH4+ adsorption at equilibrium (Qe) and NH4+ desorbed (Qde). The results for T3 for Qe and Qde were 3.88 mg L−1 and 3.80 mg g−1, respectively, for the 400 mg N L−1 isonormal solution followed by T2 with values of 3.46 mg L−1 and 3.30 mg g−1, respectively. For treatments T2 and T3 that resulted in higher Qe and Qde for NH4+, soil was not included. However, in practical terms, any of the treatments T4, T5 and T6 that included mixing the amendments with soil are better since the results of these treatments were not significantly different in terms of Qe and Qde for NH4+. This is despite the fact that T4, T5 and T6 resulted in lower Qe and Qde for NH4+ compared to T2 and T3. The results also showed a positive linear relationship between NH4+ adsorption and the addition of N. This indicates that NH4+ can be retained temporarily by the amendments. The insignificant R2 (ranging from 0.10 to 0.38) of the Langmuir regression equations suggest that the NH4+ adsorption data did not fit the Langmuir isotherms well. Future studies could explore fitting the NH4+ sorption data into other sorption models. The higher adsorption of NH4+ by the treatment with charcoal is related to its high number of adsorption sites or negative charges of these materials. Incorporating charcoal and sago bark ash as soil amendments in agriculture has the potential to reduce the usage of chemical fertilizers. The reliance on commercial lime could also be reduced due to the alkaline characteristics of these materials. Therefore, the co-application of charcoal and sago bark ash could contribute to improve the utilization of N fertilizer by effectively controlling NH4+ availability for timely crop use, reducing losses, and preventing soil and water pollution.

Abstract Quaternary quantum dots (QDs) have recently gained more attention due to their low toxicity, tunable wavelength, reduced or no blueshift emission upon overcoating, improved photoluminescence (PL) quantum yield, and PL lifetime when compared to their binary (II–VI) and ternary (I–III–VI) counterparts. In this work, the aqueous synthesis of ZnCuInS/ZnS–ZnS multi-shell quaternary QDs as a nanosensor for the selective detection of Cu2+ ions was reported. The as-synthesized QDs were spherical, with a particle diameter of 3.66 ± 0.81 nm, and emitted in the first near-infrared window (725 nm) with an average decay PL lifetime of 43.69 ns. The X-ray diffraction analysis showed that the QDs were of the wurtzite structure, while the Fourier transform infrared spectroscopy confirmed GSH capping through the sulphur–metal bond. Furthermore, the fluorometric study shows that the developed multi-shell QDs were selective towards Cu2+ ions compared to other metal ions via fluorescence quenching with a limit of detection of 1.4 µM, which is below the acceptable limit in drinking water.

L’imagerie par fluorescence (IF) et l’imagerie de résonance magnétique (IRM) comptent parmi les outils de diagnostic les plus efficaces. Dans ce contexte, des QDs possédant à la fois des propriétés fluorescentes et magnétiques sont d’un grand intérêt en tant que sondes bimodales. Dans ce travail, des QDs Ag-In-Zn-S (AIZS) et Ag-In-Ga-Zn-S (AIGZS) ont été préparés et dopés afin de développer de nouvelles sondes de sondes bimodales pour l’IF et l’IRM. Des QDs AIZS très fluorescents ont été préparés en milieu organique à l’aide de DDT et d’OAm comme ligands. Les QDs Mn:AIZS possèdent des propriétés paramagnétiques et superparamagnétiques. Les QDs AIZS et Mn:AIZS ont également été transférés en phase aqueuse à l’aide du polymère amphiphile PMAO. Par la suite, des QDs AIZS dopés Mn, Gd ou Fe ont été préparés en milieu. Des études toxicologiques et d’imagerie ont montré une bonne biocompatibilité avec les cellules KB ainsi que le fort potentiel de ces nanocristaux pour l’IF. Dans la dernière partie de ce travail, des QDs AIGZS and Mn:AIGZS QDs ont été préparés via un procédé de décomposition thermique n’utilisant qu’un seul précurseur. Ces QDs possèdent de très bonnes propriétés optiques et magnétiques. Les QDs dopés Mn ont été transférés en phase aqueuse et ont montré un fort potentiel comme agent de contraste pour l’imagerie T1 et T2
Since fluorescence imaging (FI) and magnetic resonance imaging (MRI) are among the most effective diagnostic tools, QDs with fluorescent and magnetic properties are of great interest as dual-modal probes. In this work, undoped and doped Ag-In-Zn-S (AIZS) and Ag-In-Ga-Zn-S (AIGZS) QDs were synthesized and investigated as bimodal probes for FI and MRI. Highly fluorescent AIZS QDs were prepared in organic media using DDT and OAm as capping ligands. Mn:AIZS QDs showed paramagnetic and superparamagnetic properties. AIZS and Mn:AIZS QDs were also transferred into aqueous phase using the amphiphilic PMAO polymer. Further, Mn, Gd or Fe-doped AIZS QDs were prepared in aqueous media, showed low cytotoxicity toward KB cells, and demonstrated potential as fluorescent probes for FI. Finally, AIGZS and Mn:AIGZS QDs, synthesized via a novel single precursor thermal decomposition method, showed high fluorescence and paramagnetic/superparamagnetic properties. Mn-doped aqueous transferred AIGZS QDs increased contrast in both T1-weighted and T2-weighted images with increasing in Mn loading