Thermally Brightened CdSe/ZnS Quantum Dots as Noncontact Probes for Surface Chemistry Studies of Dark Nanoparticles Trapped in the Gas Phase

• Published in: Journal of physical chemistry. C 2015-07, Vol.119 (26), p.14561-14570
• Main Authors: Howder, Collin R, Long, Bryan A, Bell, David M, Anderson, Scott L
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp5109027

Charged CdSe/ZnS quantum dots (QDs) trapped in the gas phase are transformed by CO2 laser heating, resulting in brightening of their photoluminescence intensities by more than 2 orders of magnitude. The transformation is shown to be thermally driven, and self-limiting, i.e., once the QDs have been fully brightened, they are unaffected by further CO2 laser irradiation at intensities up to 1 kW/cm2. The transformation clearly involves loss of the 10.6 μm chromophore, which appears to be the ligand layer. The thermally brightened QDs are tested for use as noncontact probe particles, allowing dark nanoparticles to be detected by cotrapping them with a brightened QD. We show that cotrapping has negligible effect on the secular frequency of the cotrapped particles, and that it is possible to simultaneously monitor changes in the mass and charge of up to three cotrapped nanoparticles for hours, allowing the rate of surface reactions to be measured. Application to studying the surface chemistry of free nanoparticles is discussed.