Silica Coated Colloidal Semiconductor Quantum Dot Supracrystal Microlasers

Abstract

A novel approach for synthesizing silica-coated colloidal quantum dot supracrystal microsphere lasers is demonstrated. These lasers consist of red-emitting CdSxSe1-x/ZnS quantum dots that act as both the laser medium and the cavity, and have great potential for biosensing, bioimaging, and integrated photonics.

Biotinylated Photocleavable Semiconductor Colloidal Quantum Dot Supraparticle Microlaser

“…The SPs in this work were synthesized using a previously reported oil-in-water emulsion technique demonstrated schematically in Figure a. , The SPs are composed of oleic acid functionalized red emitting (Figure b) CdS x Se 1– x /ZnS colloidal quantum dots (CD bioparticles) with a diameter of 5.5–6.5 nm as can be seen in the transmission electron microscope image (Figure S1). The oil phase which contains the quantum dots is emulsified with an aqueous solution containing the surfactant polyvinyl alcohol.…”

“…To overcome this, we have developed a method to coat the SPs in a silica shell (SP/SiO 2 -NH 2 ) which serves three purposes: allows for water solubility; acts as a platform for further functionalization; and potentially reduces the toxicity of the SPs. 8,13 To demonstrate the possible applications of such a system, we functionalized silica-coated SP lasers with a biotinylated photocleavable ligand (SP/SiO 2 -PC-biotin). Biotin has been used due to its strong affinity to avidin which is commonly used in the development of sensitive assays.…”

“…Although much larger in size compared to single CQDs, micrometer-sized particles still have excellent uptake in tissue. − Due to the high refractive index of the CQD material which forms the SPs, the SPs act as optical antennas or resonators and enhance the light absorption and emission compared to individual or dilute CQDs. Furthermore, with the CQDs acting as both the gain material and optical cavity, SPs demonstrate laser oscillation upon optical pumping. − In comparison to CQDs, SPs therefore offer enhanced light emission intensity, narrower spectral line widths, and the possibility for refractive index sensing due to the presence of whispering gallery lasing modes, whose properties are affected by changes in the environment at or close to the SP surface . Consequently, these CQD SPs have great potential for both in vitro and in vivo biophotonics.…”

“…However, due to the oleate molecules, the resultant SPs are insoluble in water, which prevents many of the aforementioned biological applications. To overcome this, we have developed a method to coat the SPs in a silica shell (SP/SiO 2 -NH 2 ) which serves three purposes: allows for water solubility; acts as a platform for further functionalization; and potentially reduces the toxicity of the SPs. , …”

“…Furthermore, with the CQDs acting as both the gain material and optical cavity, SPs demonstrate laser oscillation upon optical pumping. 8 − 11 In comparison to CQDs, SPs therefore offer enhanced light emission intensity, narrower spectral line widths, and the possibility for refractive index sensing due to the presence of whispering gallery lasing modes, whose properties are affected by changes in the environment at or close to the SP surface. 12 Consequently, these CQD SPs have great potential for both in vitro and in vivo biophotonics.…”