XRD results demonstrated the formation of hexagonal wurtzite structure for L-cysteine and cubic zinc blende structure for mercaptopropionic acid capped CdSe/CdS/ZnS quantum dots. On the quantum dots has been confirmed from Fourier transform infrared spectroscopy (FTIR). The capping of L-cysteine and mercaptopropionic acid The structural, morphologicalĪnd optical properties of these quantum dots have been examined through X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-Visible absorption spectroscopy (UV-Vis) and Photoluminescence spectroscopy (PL). The biocompatibility of the assynthesized quantum dots have also been analyzed through the cytotoxicity study using MTT assay. This article emphasizes on the aqueous synthesis of water soluble CdSe/CdS/ZnSĬore/shell/shell quantum dots with L-cysteine and mercaptopropionic acid as capping agent and their observed properties have been compared. The research was published in Nature Communications ( doi: 10.1038/ncomms5148).įor more information, visit dots have now become the most important candidates and widely exploited as promising architectures for use as diagnostic and imaging agents in biomedicine and as semiconductors in the electronics industry. “Applied together, these strategies might provide a practical route to nanostructures exhibiting carrier multiplication performance approaching the limits imposed by energy conservation.” “Further enhancement in carrier multiplication should be possible by combining this new approach with other demonstrated means for increasing multicarrier yields, such as by using shape control (as in nanorods) and/or materials in which cooling is already naturally slower,” said Dr. The researchers also plan to study the concept of carrier multiplication engineering through control of intraband cooling. “This shows that intraband cooling is slowed down dramatically, so that holes reside in the shell long enough to produce emission.” “A striking feature of the thick-shell PbSe/CdSe quantum dots is fairly bright visible emission, from the shell, observed simultaneously with the infrared emission from the core,” said Qianglu Lin, a CASP student working on the study. With conventional quantum dots, carrier multiplication is not efficient enough to boost the power output of practical devices. “This lost energy can be recovered by converting it into additional photocurrent via carrier multiplication.” “Typical solar cells absorb a wide portion of the solar spectrum, but because of the rapid cooling of energetic, or hot, charge carriers, the extra energy of blue and ultraviolet solar photons is wasted in producing heat,” said CASP director Dr. Courtesy of CASP/Los Alamos National Laboratory. This illustration shows core/shell PbSe/CdSe quantum dots (a) and a carrier multiplication pathway (b) in nanostructures. This combination has allowed the researchers to better understand the effect of slowed carrier cooling. While conventional quantum dots are made of lead selenide (PbSe), the CASP team’s nano-engineered quantum dots are made of a PbSe core and a thick cadmium selenide (CdSe) shell. In a new study, a team from the Center for Advanced Solar Photophysics (CASP) at Los Alamos National Laboratory has demonstrated that nano-engineered quantum dots can significantly increase charge carrier multiplication - in which a single photon excites multiple electrons and holes - compared to conventional quantum dots. This could potentially create a new generation of solar cells. LOS ALAMOS, N.M., JA new approach to building quantum dots has shown considerable gains in generating photocurrent.
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