Issue 8, 2017

CdS/ZnS core–shell nanocrystal photosensitizers for visible to UV upconversion

Abstract

Herein we report the first example of nanocrystal (NC) sensitized triplet–triplet annihilation based photon upconversion from the visible to ultraviolet (vis-to-UV). Many photocatalyzed reactions, such as water splitting, require UV photons in order to function efficiently. Upconversion is one possible means of extending the usable range of photons into the visible. Vis-to-UV upconversion is achieved with CdS/ZnS core–shell NCs as the sensitizer and 2,5-diphenyloxazole (PPO) as annihilator and emitter. The ZnS shell was crucial in order to achieve any appreciable upconversion. From time resolved photoluminescence and transient absorption measurements we conclude that the ZnS shell affects the NC and triplet energy transfer (TET) from NC to PPO in two distinct ways. Upon ZnS growth the surface traps are passivated thus increasing the TET. The shell, however, also acts as a tunneling barrier for TET, reducing the efficiency. This leads to an optimal shell thickness where the upconversion quantum yield (ΦUC) is maximized. Here the maximum ΦUC was determined to be 5.2 ± 0.5% for 4 monolayers of ZnS shell on CdS NCs.

Graphical abstract: CdS/ZnS core–shell nanocrystal photosensitizers for visible to UV upconversion

Supplementary files

Article information

Article type
Edge Article
Submitted
11 Apr 2017
Accepted
30 May 2017
First published
31 May 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2017,8, 5488-5496

CdS/ZnS core–shell nanocrystal photosensitizers for visible to UV upconversion

V. Gray, P. Xia, Z. Huang, E. Moses, A. Fast, D. A. Fishman, V. I. Vullev, M. Abrahamsson, K. Moth-Poulsen and M. Lee Tang, Chem. Sci., 2017, 8, 5488 DOI: 10.1039/C7SC01610G

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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