Synthesis of Ternary and Quaternary Au and Pt Decorated CdSe/CdS Heteronanoplatelets with Controllable Morphology

Abstract

1 of 11) 1604685 separation, the mixing of electronic states, and how synergistic properties of metals and the semiconductors occur in the same particle. [1b,2] The great advantage of ultrafast electron transfer and charge carrier (electron-hole) separation at the metalsemiconductor interface has motivated researchers to discuss applications in, e.g., photocatalytic water splitting, [3] pollutant degradation, [4] field effect transistors, [5] CO 2 reduction reactions, [6] etc. The metal-decorated nanostructures are also employed for self-assembling in solutions or on substrates to measure their electrical transport properties. [7] Various synthetic approaches (such as reduction, thermal annealing, photoinduced reactions, nanowelding, and many others) have enabled scientists to produce nanoheteroparticles with many possible combinations of metals (e.g., Au, Pt, Pd, Ni, or Co) and different shapes of metal-chalcogenide semiconductors, starting from spherical dots, [2a,3b,4c,8] nanorods, [1b,2b,9] nanowires, [9a] tetrapods, [1b,10] and pyramids, [11] to cubes [4b,12] and many more. [9g,13] In some cases, selective deposition of the metal domains (Au, Pt, Ag, Ni, Co, or Cu) at one end or both ends of the nanorods, at the tips of tetrapods, or only at the sides of rod-shaped semiconductor domains are shown in literature. [2a,9b,14] A variety of new ternary and quaternary metal-semiconductor inorganic nanostructures with unprecedented structural morphologies is achieved by the decoration of five monolayer-thick CdSe/CdS core/crown nanoplatelets with Au and Pt domains. Significant differences in metal growth behavior are observed by varying the CdSe core and the CdS crown dimensions. Depending on the core size, Au growth can be directed only to the CdS edges, or both at the edges and at the center of the nanoplatelets. In contrast, the nucleation of Pt domains always happens at the CdS edges independently of the core and crown dimensions. Furthermore, quaternary structures are obtained by additional Au growth on Pt-decorated CdSe/CdS nanoplatelets, where the effect of steric hindrance of the existing Pt domains results in the Au nucleation to occur only at the CdSe core. Instead, a change in the order of growth of the two noble metals results in Pt-Au alloys present only at the surrounding edges of the nanoplatelets. Additionally, the metal-decorated nanoplatelets are found to be efficient catalysts for H 2 fuel generation under white light irradiation. The highest apparent quantum efficiency measured is 19.3% ± 1.4% with a turnover frequency of ≈10 5 molecules of H 2 per hour per nanoplatelet.

Spectroelectrochemical Investigation of the Charge Carrier Kinetics of Gold‐Decorated Cadmium Chalcogenide Nanorods

“…The absorption spectra of gold decorated CdSe/CdS NRs was measured in an integration sphere to eliminate the effect of scattering at higher wavelengths. Comparable absorption spectra for metal decorated metalchalcogenide nanoparticles have been found in literature ,,. ITO itself absorbs photons in the UV/Vis regime (see Supporting Information Figure SI‐7).…”

“…Recently metal‐semiconductor nano‐heteroparticles moved in the centre of interest due to their efficient electron hole separation ability and better charge transfer performance ,. Recent transient absorption studies suggest that the separation of charge carriers in CdSe/CdS systems by noble metal domains leads to the increase of the exciton lifetime from the nanosecond to the microsecond timescale .…”

Cadmium Chalcogenide Nano‐Heteroplatelets: Creating Advanced Nanostructured Materials by Shell Growth, Substitution, and Attachment

“…2D CdSe nanocrystals were decorated with gold, platinum, and palladium nanoparticles, CdSe/CdS dot‐in‐plate nano‐heteroplatelets were decorated with gold, and CdSe/CdS core/crown heterostructures were decorated with gold and platinum . Depending on the noble metal used and the type of precursor, heterostructures with different morphologies can be obtained: metal particles can assemble at the corners, on the large or small sides of the nanoplatelet, or along its entire perimeter.…”

“…Multicomponent heterostructures: f) Core/crown CdSe/CdS nanoplatelets with a small core and a large crown, decorated with Pt and g) core/crown CdSe/CdS nanoplatelets with a large core and small crown, decorated first with Pt and then with Au. Reproduced with permission . Copyright 2017, WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.…”

“…When gold is added to heteroplatelets that were previously decorated with platinum, four‐component complex nano‐heteroplatelets can be obtained . In such structures, a steric inconsistency effect is caused by the existing domains of Pt, which leads to Au particles appearing only on the core of the nanoplatelet, while the perimeter of its crown remains surrounded by Pt particles, as shown in Figure g.…”