RESUMO
Mild treatment with hydrogen peroxide solutions (3-30%) efficiently decomposes adsorbed chemical warfare agents (CWAs) on microporous activated carbons used in protective garments and air filters. Better than 95% decomposition of adsorbed sulfur mustard (HD), sarin, and VX was achieved at ambient temperatures within 1-24 h, depending on the H2O2 concentration. HD was oxidized to the nontoxic HD-sulfoxide. The nerve agents were perhydrolyzed to the respective nontoxic methylphosphonic acids. The relative rapidity of the oxidation and perhydrolysis under these conditions is attributed to the microenvironment of the micropores. Apparently, the reactions are favored due to basic sites on the carbon surface. Our findings suggest a potential environmentally friendly route for decontamination of adsorbed CWAs, using H2O2 without the need of cosolvents or activators.
Assuntos
Carvão Vegetal/química , Substâncias para a Guerra Química/análise , Descontaminação , Peróxido de Hidrogênio/química , Adsorção , Substâncias para a Guerra Química/química , Hidrólise , Cinética , Espectroscopia de Ressonância Magnética , Gás de Mostarda/análise , Gás de Mostarda/química , Compostos Organotiofosforados/análise , Compostos Organotiofosforados/química , Oxirredução , Sarina/análise , Sarina/química , Soluções , Temperatura , Água/químicaRESUMO
This paper focuses on the interactions between cysteamine-stabilized CdTe nanocrystals [CdTe(CA) NCs] and thioglycolic-acid-stabilized CdTe nanocrystals [CdTe(TGA) NCs]. These interactions were examined by the absorption, continuous, and time-resolved photoluminescence (PL) spectra of the electrostatically mixed and the covalently linked NCs assemblies comprised of the oppositely surface charged CdTe(CA) and CdTe(TGA) NCs and by a comparison with those of the corresponding pristine NCs. The CdTe(CA)-CdTe(TGA) coupling is dictated by the surfactant spacer, ranging between 0.93 and 1.14 nm and by electrostatic and covalent interactions, enabling a Förster resonance energy transfer (FRET) process among the NCs. The results revealed an excellent spectral overlap between the emission of the CdTe(TGA) NCs and the absorption of the CdTe(CA) NCs as well as a PL spectral red shift on the formation of electrostatic and covalent interactions. Furthermore, the measurements showed a lifetime ranging between 1.2 and 3 ns for the electrostatically mixed and the covalently linked assemblies, shorter than those of the pristine CdTe(CA) NCs and CdTe(TGA) NCs, both of which measured as approximately 5.5 ns. When CdTe(TGA) NCs performed as the most efficient donors, FRET rates of 10(10)-10(11) s(-1) were calculated for the electrostatically mixed NCs or covalently linked NCs.
Assuntos
Cádmio/química , Nanotecnologia/métodos , Telúrio/química , Cisteamina , Estabilidade de Medicamentos , Transferência Ressonante de Energia de Fluorescência , Eletricidade Estática , TermodinâmicaAssuntos
Cádmio/química , Nanopartículas Metálicas/química , Nanopartículas/química , Nanopartículas/classificação , Telúrio/química , Compostos de Cádmio/química , Cristalização , Eletroquímica , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão , Nanopartículas/ultraestrutura , Nanotecnologia , Pontos Quânticos , Selênio/química , Semicondutores , Espectrofotometria , Sulfetos/químicaRESUMO
Single-exciton, biexciton, triexciton, and quadraexciton bands were resolved in the microphotoluminescence spectrum of a single CdTe/CdSe core-shell colloidal quantum dot, revealing nearly blinking-free behavior. Multiexcitons were generated by a sequential filling of electronic shells with the increase of a continuous-wave excitation power, and their probability was evaluated under steady-state conditions. A partial carriers' delocalization was determined at the core-shell interface, and an exciton binding energy was estimated by a second-order perturbation theory.