ABSTRACT
A self-assembled fluorescent nanosensor for the determination of L-cysteine (Cys) was constructed based on the mechanism of fluorescence resonance energy transfer (FRET). In this system, CdTe/ZnS QDs serve as the energy donor while AuNPs serve as the receptor, resulting in the occurrence of FRET with dramatic fluorescence quenching of the QDs (turn off). Once Cys is added, AuNPs can adsorb Cys, leading to the release of the QDs. The process would inhibit the FRET, which contributed to the recovery of fluorescence (turn on) and an off-on fluorescence aptasensor for Cys detection was constructed accordingly. The linear response range of the fluorescence sensor is from 0.8 to 50 µM, and the detection limit is 0.24 µM. The sensor demonstrates great sensitivity and selectivity to Cys. More importantly, the QD-based sensing platform was successfully used for the detection of Cys in milk samples with high precision and accuracy, indicating the potential of the probe in practical applications.
Subject(s)
Cadmium Compounds , Metal Nanoparticles , Quantum Dots , Cysteine , Fluorescence Resonance Energy Transfer , Gold , Tellurium , Coloring AgentsABSTRACT
A Fe3+ optical sensor (CdTe@γ-CD@RBD) has been developed by using gamma-cyclodextrin (γ-CD) as a bridge to link CdTe quantum dots (QDs) and a Rhodamine B derivative (RBD). The RBD molecule can enter the cavity of the γ-CD anchored onto the surfaces of the QDs. In the presence of Fe3+, the fluorescence resonance energy transfer (FRET) process from QDs to RBD will be initiated, rendering the nanoprobe to display a response to Fe3+. The degree of fluorescence quenching presented a satisfactory linearity between 10 and 60 µΜ with the incremental concentrations of Fe3+, and the calculated limit of detection was 2.51 µΜ. Through sample pretreatment procedures, the probe has been used in the determination of Fe3+ in human serum. The average recoveries in the spiking levels are ranged from 98.60 % to 107.20 % with a relative standard deviation of around 1.43 %-2.96 %. This finding leads to a method for fluorescent detection of Fe3+ with high sensitivity and exceptional selectivity. We believe that this study can give a new insight into the rational design and application of FRET-based nanoprobes.
Subject(s)
Cadmium Compounds , Quantum Dots , gamma-Cyclodextrins , Humans , Fluorescence Resonance Energy Transfer/methods , Tellurium , Fluorescent DyesABSTRACT
High energy density materials (HEDM) are the subject of an extensive research effort in relation to the use of these compounds as components of rocket propellants, powders, and formulations of high-performance explosives. Hexanitrohexaazaisowurtzitane (HNIW, i.e., CL-20) has received much attention in these research fields for its specific impulse, burning rate, ballistics, and detonation velocity. In this paper, the development and performances of the explosives from the first to the fourth generation are briefly summarized, and the synthesis status of the fourth-generation explosive, HNIW, is reviewed. The key issues that restrict the development of industrial amplification synthesis of HNIW are analyzed, and the potential directions of development are proposed. It is pointed out that to synthesize new and efficient catalysts is the key to making the cost-effective manufacturing of CL-20 a reality.
ABSTRACT
A novel multi-azido ether energetic plasticizer 1,2,8,9-tetraazido-4,6-dioxol-nonane (TADONA) was designed and synthesized through consecutive azidonation and condensation reactions, and its structure was characterized and confirmed by NMR and FT-IR spectroscopy, as well as elemental analysis. Its impact sensitivity was measured as 25.2 J, friction sensitivity was measured as 160 N, its thermal decomposition peak temperature was 236.2 °C, and its glass transition temperature (Tg) was -88.9 °C, which indicated that TADONA was mechanically insensitive with good thermal stability and excellent low-temperature properties. Theoretical calculations indicated that TADONA possessed energetic properties superior to some reported azide plasticizers and good miscibility with glycidyl azide polymer (GAP). Moreover, a notable effect on the adjustment of the viscosity of GAP was attributed to TADONA, and the higher the content of TADONA in GAP, the more optimal the adjustment effect that was achieved. Furthermore, the Tg for TADONA + GAP (1 : 10), TADONA + GAP (2 : 10), TADONA + GAP (3 : 10), and TADONA + GAP (4 : 10) was determined as -54.4 °C, -58.8 °C, -61.9 °C, and -65.8 °C, respectively, which were much lower than that of GAP (-49.1 °C). Therefore, TADONA exhibited an excellent plasticizing effect on GAP, demonstrating considerable application potential in GAP-based propellants and explosives.
