Influencing the coupling between network building blocks in CdSe/CdS dot/rod aerogels by partial cation exchange

Abstract

The assembly of CdSe/CdS dot/rod nanocrystals (NCs) with variable length of ZnS tip into aerogel networks is presented. To this end, a partial region selective cation exchange procedure is performed replacing Cd by Zn starting at the NC tip. The produced aerogel networks are investigated structurally and optically. The networks of tip-to-tip connected NCs have an intricate band structure with holes confined to the CdSe cores while electrons are delocalized within the CdS also within connected building blocks. However, the ZnS tips act as a barrier of variable length and strength between the NC building blocks partly confining the electrons. This results in NC based aerogel networks with tunable strength of coupling between building blocks.

Investigation of the Photocatalytic Hydrogen Production of Semiconductor Nanocrystal‐Based Hydrogels

“…During the IMPS experiments, the on–off frequency of the LED is varied (here from 10 kHz to 1 Hz) and the photocurrent response of the system is recorded. [ 51 ] Thus, it is possible to distinguish between charge transfer processes that occur on different time scales, provided their rate constant differ by at least one order of magnitude. [ 52 ] A sub‐monolayer of CdSe/CdS NRs results in only one semicircle in the Nyquist plots of the IMPS measurements (Figure 5C), which is related to the fast diffusion from electrons from the NRs to the electrode.…”

Optical properties of NIR photoluminescent PbS nanocrystal-based three-dimensional networks

“…52 Previous reports of characterized NC aerogel systems and simple QD lms can act as references for the following characterization like the inuence of the network formation onto the PL lifetime and observed shis of the emission signal. 15,17,22,[53][54][55][56] In Fig. 5 the absorption and emission spectra as well as the PL decay of the four synthesized aerogels together with the spectra and decays of the as-synthesized QDs (used for the aerogel synthesis) can be found.…”

“…[14][15][16][17][18][19] They are not only macroscopic materials with retained nanoscopic properties, but in addition show new properties due to the interaction of the assembled NCs. [14][15][16][20][21][22] Even though previous works made efforts to synthesize aerogels from infrared NCs, such as PbS, PbSe and PbTe, their properties and especially their photoluminescence (PL) have never been investigated in depth. 17,19,[23][24][25][26][27] So far, only in one single case, the NIR-emission of an acetogel has been reported, which was synthesized by cation exchange.…”

Nanoparticle-Based Aerogels and Their Prospective Future Applications

“…Another interesting method for coupling and gelation of CdSe/CdS dot/rod with variable length of ZnS tips in NPAs is presented by Bigall et al 55 A partial sector selective cation exchange procedure is performed in which Cd is replaced by Zn, starting at the NP tips. The networks of tip-to-tip connected NPs have a complicated band structure with holes confined to the CdSe cores, while electrons are delocalized within the CdS and the ZnS tips acting as barriers between the NC building blocks partly confining the electrons.…”