Synthesis and nonlinear optical characterization of SnO2 quantum dots

Dendrimer-Templated Synthesis and Characterization of Tin Oxide Quantum Dots Deposited on a Silica Glass Substrate

“…Because the size of the synthesized QDs, measured by TEM and AFM, were smaller than the exciton Bohr radius of tin oxide (a B = 2.7 nm), the increase in the band gap energy was assigned to the quantum confinement effect. 13,15,17 We also differentiated the UV−vis adsorption spectra to evaluate the absorption peaks (Figure 5b). The spectra were predicted to have two components (Figure 5b, blue and red regions).…”

“…II–VI and III–V semiconductor QDs, such as CdSe and GaAs, have been widely studied. − However, replacing such toxic materials with other nontoxic semiconducting materials has been required because of environmental problems. From this point of view, tin oxide QDs have attracted attention as the candidate for cadmium-free QDs because of their low cost and environmental friendliness. − Among several tin oxide compounds, SnO 2 is known as the most stable phase under ambient conditions, and as an n-type wide band gap semiconductor (3.6 eV at 300 K for bulk state) with a rutile-type crystalline structure (space group no. 136; P 4 2 / mnm ) and with an exciton Bohr radius ( a B ) of 2.7 nm. , SnO 2 is a nonstoichiometric compound, and also metastable phases, such as SnO, Sn 3 O 4 , Sn 2 O 3, and others, are known.…”

“…Previously synthesized tin oxide QDs have wide size distributions and the obtained information from measurements might be averages of the size distribution. − We have demonstrated that the dendrimer-templating method can be used to synthesize tin oxide QDs with a narrow size-distribution in a mesoporous silica support . However, the obtained physical properties were limited, as shown by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), because of the low tin oxide content (0.2–1.2 wt %) and the low transparency of the substrate.…”

SnO2 Quantum Dots Synthesized with a Carrier Solvent Assisted Interfacial Reaction for Band-Structure Engineering of TiO2 Photocatalysts

“…Their applications in biomedical imaging, solar cells, light-emitting diodes, etc., have received great success. Consequently, there have been developed a wide variety of synthetic methods for QDs production, including laser ablation, microwave-assisted, hydrothermal, wet chemistry, thermal evaporation, sonochemical precipitation, and sol–gel processes . Most of the methods however require either high temperatures and long reaction times or high power energy input.…”

“…In this work, we propose to resolve this issue by using SnO 2 QDs as the second semiconductor. The band gap of SnO 2 QD gets enlarged with decreasing QD size because of the quantum confinement effect. − , With the enlargement of the band gap, the energy level of the corresponding conduction band shifts to the more negative region and can be adjusted to fall within the workable energy gap through control of the QD size. For the above idea to work, one needs to be able to control the size of the SnO 2 QD precisely.…”