Photochemical Fine-Tuning of Luminescent Color of Cadmium Selenide Nanoparticles:  Fabricating a Single-Source Multicolor Luminophore

Abstract

Size-selective photoetching was applied to silica-coated cadmium selenide (SiO 2 /CdSe) nanoparticles to precisely control their photoluminescence properties. The absorption spectra of CdSe was blue-shifted by irradiation of monochromatic light, and finally, the absorption onset agreed with the wavelength of irradiation light, indicating that CdSe particles were photoetched to smaller ones until the irradiated photons were not absorbed by the photoetched particles and that the SiO 2 shell layer surrounding the CdSe core prevented coalescence between the photoetched particles. Although as-prepared SiO 2 /CdSe did not exhibit photoluminescence, the application of size-selective photoetching to SiO 2 /CdSe resulted in the development of the band gap emission, with the degree being enhanced with progress of the photoetching. The peak wavelength of photoluminescence decreased with a decrease in the wavelength used for the photoetching, so that the luminescence color could be tuned between red and blue. Partial photoetching of SiO 2 /CdSe nanoparticle films produced intense band gap emission of CdSe at the photoetched area, while the remainder of the SiO 2 / CdSe films did not exhibit detectable photoluminescence, resulting in the formation of a clear photoluminescence image under UV irradiation. This technique makes it possible to produce a multicolored photoluminescence image by irradiation with monochromatic lights having various wavelengths using a single source material.

Stochastic processes in light-assisted nanoparticle formation

“…In addition, such desorption is induced with a high probability when the formed QDs reach a particular diameter. This light-dependent QD size regulation has also been reported in other material systems, such as CdSe 10 and Si. 11 The insets in Fig.…”

Nanostructure Engineering of Size-Quantized Semiconductor Particles for Photoelectrochemical Applications

“…The size distribution of the photoetched particles was much narrower than that of the original particles, the standard deviation of size distribution being less than 10% of the average diameter. The sizeselective photoetching technique has been widely used to control the size of quantized nanoparticles such as ZnO, 29 ZnS, 30 CdS, 26,27,31 CdSe, 32 CdTe, 33 InP, 34 InGaN, 35 and AgInS 2 nanoparticles. 21 However, being different from the case of photoetching CdS particles, an additional complexing agent such as NH 3 was necessary to successfully complete size-selective photoetching of AgInS 2 nanoparticles, because Ag + ions released along with the photoetching formed an insoluble Ag 2 O passivation layer on the particle surface to prevent further photoetching of AgInS 2 .…”

“…37 Furthermore, this technique was advantageous for controlling the core size of core-shell-structured nanoparticles after being constructed. 32,[38][39][40][41][42][43][44][45] Figure 4 shows transmission electron microscope (TEM) images of CdS core-SiO 2 shell nanocomposite particles (CdS@SiO 2 ) before and after size-selective photoetching. 38 Each original composite particle had a CdS core with average diameter of 5.0 nm, which was in contact with a thin amorphous SiO 2 shell.…”

“…Figure 6a shows pictures of photoluminescent CdSe@SiO 2 colloid in an aqueous solution. 32 With a decrease in the wavelength of irradiation light from 630 to 514 nm, the CdSe cores in core-shell particles were photoetched to smaller particles, so that the PL color changed from red to blue with a blue shift of the PL peak wavelength from 630 to 494 nm. Although PL was scarcely observed for as-prepared CdSe@SiO 2 , photoetching of the CdSe core in the composite particles enhanced the PL intensity.…”

Electrochemical Synthesis of CdSe Nanoparticles Using a Se-modified RVC Electrode and Mercaptoacetic Acid as a Stabilizer

“…[1][2][3][4] Among them, CdSe nanoparticles are of much interest because of applications in solar photovoltaic cells, sensors and optoelectronic devices. [5][6][7][8][9][10][11] CdSe NPs have been extensively studied following the development of chemical preparation procedures using hot trioctylphosphine oxide (TOPO) as a capping agent. 3 Unlike the original method which employed toxic dimethyl cadmium as a cadmium source, other researchers have developed a "green synthesis" route and they synthesized CdSe NPs using CdO as a precursor.…”