Alloyed ZnxCd1-xSe quantum dots (QDs) have been successfully prepared at low temperatures by reacting a mixture of Cd(ClO4)2 and Zn(ClO4)2 with NaHSe using cysteine as a surface-stabilizing agent. The photoluminescence (PL) spectra of the alloyed QDs are determined on the basis of the Zn2+/Cd2+ molar ratio, reaction pH, intrinsic Zn2+and Cd2+ reactivities toward NaHSe, concentration of NaHSe, and the kind of thiols. A systematic blue shift in emission wavelength of the alloyed QDs was found with the increase in the Zn mole fraction. This result provides clear evidence of the formation of ZnxCd1-xSe QDs by the simultaneous reaction of Zn2+ and Cd2+ with NaHSe, rather than the formation of separate CdSe and ZnSe nanocrystals or core-shell structure CdSe/ZnSe nanocrystals. The size and inner structure of these QDs are also corroborated by using high-resolution transmission electron microscopy and X-ray powder diffraction. To further understand the formation mechanism, the growth kinetics of Zn0.99Cd0.01Se was studied by measuring the PL spectra at different growth intervals. The results demonstrated that, in the initial stage of growth, Zn0.99Cd0.01Se has a structure with a Cd-rich core and a Zn-rich shell. The post-preparative irradiation of these QDs improved their PL properties, resulting in stronger emission.

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Supplementary Materials: Stable1. Bond Lengths (Å) and Anglse (deg) for Cd(1) and Cd(2) Coordination Spheres in complex 1 a. Stable2. Bond Lengths (Å) and Anglse (deg) for Zn(1) and Zn(2) Coordination Spheres in complex 2. Sfigure1. (a) Distorted pentagonal bipyramidal coordination sphere about Cd(1) with atom labeling scheme. (b) Distorted octahedral coordination sphere about Cd(2) with atom labeling scheme (ORTEP drawing, 50 % thermal ellipsoids). Sfigure2. Distorted octahedral coordination sphere about (a) Zn(1) and (b) Zn(2) with atom labeling scheme (ORTEP drawing, 50 % thermal ellipsoids). Stable 1. Bond Lengths (Å) and Anglse (deg) for Cd(1) and Cd(2) Coordination Spheres in complex 1 a Cd(1)−O(1) 2.569(4) Cd(2)−O(1) 2.418(4) Cd(1)−O(2) 2.363(3) Cd(2)−O(5) 2.339(4) Cd(1)−O(3) i 2.398(3) Cd(2)−O(9) ii 2.325(4) Cd(1)−O(4) i 2.431(3) Cd(2)−O(10) ii 2.319(4) Cd(1)−O(6) 2.469(4) Cd(2)−O(11) w 2.257(4) Cd(1)−O(10) 2.292(4) Cd(2)−N(2) 2.268(5) Cd(1)−N(1) 2.248(5)

Photoconductivities (PCs) with high responsivity in two-dimensional (2D) diindium triselenide (In 2 Se 3 ) nanostructures with α-phase hexagonal structure were studied. The In 2 Se 3 nanosheet photodetectors fabricated by focused-ion beam technique exhibit broad spectral response with wavelength range from 300 nm to 1000 nm. The In 2 Se 3 nanosheets achieve optimal responsivity of 720 A W −1 in near-infrared region (808 nm), and detectivity of 2.2 × 10 12 Jones, which were higher than several 2D material photodetectors. The physical origins that result in high photoresponse in In 2 Se 3 nanosheets such as carrier lifetime and mobility were also characterized by time-resolved PC and field-effect transistor measurements. The fast (hundred microseconds to milliseconds) and slow (seconds and longer) current rise or decay processes were both observed during the photoresponse. The narrowing (or relaxation) of depletion region and oxygen-sensitized photoconduction mechanism were suggested to be the causes of the efficient photoresponse in the In 2 Se 3 nanostructure detectors. All these observations suggest that α-In 2 Se 3 nanosheets could be a promising candidate for photosensitive material applications.

A new composite of poly(diallyldimethylammonium chloride) (PDDAC) and glutathione-capped ZnHgSe quantum dots (GSH-QDs) has been developed for sensing Cu 2+ in aqueous solution on the basis of fluorescence quenching. The formation of the composite is dominated through the electrostatic interaction between cationic PDDAC and anionic GSH-QDs. When Cu 2+ collides with PDDA/GSH-QDs composites, Cu 2+ displaces the Zn and/or Hg in the ZnHgSe QDs and forms extremely low soluble particles of CuSe onto the surface of QDs. As a result, the fluorescence intensity of QDs is quenched efficiently. Compared to GSH-QDs, PDDA/GSH-QDs composites exhibited better selectivity toward Cu 2+ as a result of minimizing the electrostatic interaction between metal ions and the ligands. The selectivity of PDDA/GSH-QDs composites toward Cu 2+ was further improved by increasing glycine concentration and optimizing the pH of the solution. Under the optimal conditions, PDDA/GSH-QDs composites provided the limits of detection for Cu 2+ at a signal-to-noise ratio of 3 of 0.2 nM (~2.0 ppt). We believe that this probe has great potential for the detection of Cu 2+ in environmental waters.

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