Visible Light Catalysis-Assisted Assembly of Ni_h-QD Hollow Nanospheres in Situ via Hydrogen Bubbles

Abstract

Hollow spheres are one of the most promising micro-/nanostructures because of their unique performance in diverse applications. Templates, surfactants, and structure-directing agents are often used to control the sizes and morphologies of hollow spheres. In this Article, we describe a simple method based on visible light catalysis for preparing hollow nanospheres from CdE (E = Te, Se, and S) quantum dots (QDs) and nickel (Ni(2+)) salts in aqueous media. In contrast to the well-developed traditional approaches, the hollow nanospheres of QDs are formed in situ by the photogeneration of hydrogen (H2) gas bubbles at room temperature. Each component, that is, the QDs, metal ions, ascorbic acid (H2A), and visible light, is essential for the formation of hollow nanospheres. The quality of the hollow nanospheres depends on the pH, metal ions, and wavelength and intensity of visible light used. Of the various metal ions investigated, including Cu(+), Cu(2+), Fe(2+), Fe(3+), Ni(2+), Mn(2+), RuCl5(2-), Ag(+), and PtCl4(2-), Ni(2+) ions showed the best ability to generate H2 and hollow-structured nanospheres under visible light irradiation. The average diameter and shell thickness of the nanospheres ranged from 10 to 20 nm and from 3 to 6 nm, respectively, which are values rarely reported in the literature. Studies using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma-mass spectroscopy (ICP-AES), and steady-state and time-resolved spectroscopy revealed the chemical nature of the hollow nanospheres. Additionally, the hollow-structured nanospheres exhibit excellent photocatalytic activity and stability for the generation of H2 with a rate constant of 21 μmol h(-1) mg(-1) and a turnover number (TON) of 137,500 or 30,250 for CdTe QDs or nickel, respectively, under visible light irradiation for 42 h.

Branched Polyethylenimine Improves Hydrogen Photoproduction from a CdSe Quantum Dot/[FeFe]‐Hydrogenase Mimic System in Neutral Aqueous Solutions

“…[16,28,[31][32][33][40][41][42] MPA-CdSe QDs are attractive on account of the broad and intense absorption in visible-light region, aqueous dispersion, rich surface-binding properties, and simple preparation. [40][41][42][43][44] The branched PEI, a widely used polymer to mimic environment of biological system, [45][46][47] contains a large number of primary, secondary, and tertiary amino groups, and features good water-solubility and proton sponge behavior in a broad pH range. Significantly, the amino groups not only can be protonated even under high pH condition (pH < 10) in water, [48,49] but also are ideal reactive sites to covalently bind a [FeFe]-H 2 ase mimic.…”

Layered Double Hydroxide Nanostructured Photocatalysts for Renewable Energy Production

“…Ti-containing LDH compounds contain a M 2+ -O-Ti 4+ network, in which MO 6 and TiO 6 octahedra are bonded to each other through metal oxo bridging. By controlling the particle Moreover, by incorporating defects in LDH systems, dramatic electronic structure changes can be realized in comparison with defect-free bulk LDH.…”

“…By harvesting solar energy that is generally abundant everywhere on Earth, [1][2][3][4] semiconductor photocatalysts are expected to make an important contribution in areas such as: 1) photocatalytic water splitting to H 2 and O 2 , 2) photoreduction of CO 2 into hydrocarbon feedstocks or fuels, and 3) photocatalytic mineralization of organic pollutants. [ 5,6 ] Semiconductor photocatalysts with appropriate band gaps (E g ) and band energies (versus normal hydrogen electrode (NHE)) are capable of enhancing the rate of specifi c chemical reactions under light stimulation with E > E g . TiO 2 -based photocatalysts have been the subject of detailed investigation, owing to their excellent activities and stabilities under UV excitation.…”

Quantum Dots Based Photocatalytic Hydrogen Evolution

“…Under illumination, hollow aggregation nanoparticles were formed by QDs and Co 2 + ions, which was caused by hydrogen gas bubbles generated in situ as a template ( Figure 3). [43] Similar metal ions strategy was also used for photocatalytic hydrogen evolution from water-soluble CdSe and CdS QDs with Ni 2 + . [44,45] The catalytic center was formed by the absorption of Ni 2 + ions on the surface of mercaptopropionic acid (MPA) capped QDs, and an internal quantum yield of 11.2 % for CdSe QDs (TON 15,340 respect to QDs) and 12.2 % for CdS QDs (TON 38,405 respect to QDs) were obtained, respectively.…”