Photophysics of quantized colloidal semiconductors. Dramatic luminescence enhancement by binding of simple amines

Abstract

When extremely small ("Q state") semiconductor particles of CdS or Cd3As2 are treated with small amounts of alkylamines (e.g. N(Et)3) dramatic increases (up to 450%) in the quantum yield for exciton emission result. Similar results are found for colloids suspended in bulk (aqueous) solution, nonaqueous (2-propanol) solution, and reverse (AOT) micelles. This effect is interpreted as modification of midband gap states, probably associated with excess Cd2+, by N(Et)3 binding. Such states can dominate radiationless decay in Q state materials. When these states are modified, the quantum yield can approach unity (for Cd3As2).

Photophysics and Photocatalytic Properties of Cd(OH)2-Coated Q-CdS Clusters in the Presence of Guanine and Related Compounds

“…In a number of studies it has been observed that the modification of the surfaces of these particles by binding organics and inorganics affects their photophysics and photochemistry significantly (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Surface capping of Q-CdS by thiophenol and mercaptobenzoxazole influenced the primary photochemical events of trapping of charge carriers and their decay dynamics of recombination (9).…”

“…Thiol-modified CdS produces selectivity in the reduction of CO 2 to yield higher amounts of formate to carbon monoxide (13). Aliphatic amines (6), thio compounds (8,14), aniline (15), and tryptophan (17) are known to affect the pho- 1 To whom correspondence should be addressed.…”

Time-Resolved Spectral Observations of Cadmium-Enriched Cadmium Sulfide Nanoparticles and the Effects of DNA Oligomer Binding

“…However, the sensitivity of NP emission to the surface chemistry also suggests their use as sensors as well as tracers (13). For instance, CdS and Cd 3 As 2 display dramatic increases in emission intensity, up to 4-fold, in the presence of alkylamines (14), and CdS particles are quenched by benzyl alcohol (15). The emission of porous silicon, thought to be partially composed of Si nanoparticles, can be quenched by oxygen-containing solvents and amines (16 -18), and porous silicon can display pH-dependent intensities (19).…”

Detection of shallow electron traps in quantum-sized CdS particles using dithiolenes

“…Enhancement in the emission yield occurs when surface defects promote radiationless recombination of charge carriers which can be blocked upon surface modification [9]. Therefore, protocol of the synthesis of CdS nanoparticles is very important.…”