Strong Enhancement of PbS Quantum Dot NIR Emission Using Plasmonic Semiconductor Nanocrystals in Nanoporous Silicate Matrix

Abstract

quantum yields (PLQY), and wide tunability, combined with low material costs. [10,11] In which case the identification of an appropriate metal NIR plasmonic nanostructure is the next challenge, with only some complex gold nanostructures, such as tetrapods, [12] nanorods, [13] nanocages, [14] nanostars, [15] and faceted gold nanoparticles [16] can be cited. However, their plasmonic resonance bands are still limited in their tunable range to no longer than 1.0 µm and in addition their commercial manufacturing is highly costly. More recently, semiconductor nanocrystals with plasmonic features have attracted much attention, [17][18][19][20] with one particular example, copper deficient copper chalcogenides, [21][22][23][24][25][26][27] offering tunable plasmonic bands covering a wide range of the NIR. Plasmonic resonance in such semiconductor plasmonic nanocrystals (PNCs) arises from the excess of free holes and can be easily and reversibly tuned throughout the entire NIR spectral range. Although it is expected that near-field enhancement of optical responses by such PNCs will be less effective as compared to the noble metals in the visible range due to the smaller number of free carriers, [18] there are a few encouraging reports for PNC enhanced Raman scattering [28] and upconversion visible emission. [29] Despite the huge potential of plasmonic enhancement of NIR optical responses, especially NIR absorption and photoluminescence (PL), this topic has not been studied as of yet, with copper chalcogenides PNCs considered mostly for thermal therapy. [18,20] To realize a miniature NIR emitter which exploits plasmonic enhancement of radiation, an appropriate matrix must be selected. Such a matrix must provide optical transparency and high loading of nanoscale emitters. Importantly, the emitters and PNCs should be separated from each other to prevent PL quenching by means of nonradiative energy transfer. [1,30] At the same time, the distance between the emitter and PNC should be short enough (≈5-20 nm) to provide an effective enhancement. [1] The nanoporous silicate matrix (NSM) can satisfy these demands. [31,32] Its porous structure provides the separation between embedded QDs and PNCs, while high porosity allows the high loading of the nanoparticles.Nowadays PbS QDs are considered as a promising material for NIR photovoltaic and light-emitting devices. [33][34][35][36][37] However, the efficiency of the PbS QD light emitters is still far behind that for visible QDLEDs. [38,39] Here we report high (up to ≈20 times Strong enhancement of near-infrared (NIR) emission of lead sulfide quantum dots (QDs) induced by Cu 2−x Se semiconductor plasmonic nanocrystals (PNCs), both embedded into nanoporous silicate matrix is reported. The emission enhancement comes from resonant interaction of QD optical transition dipole with the near field of plasmons of semiconductor PNCs. Possible mechanisms of QD photoluminescence broadening and shift, including Rabi splitting and trap-state-related photoluminescence enhancement, are considered. ...

Fibre Optic SERS Probes For Remote Sensing

“…Nanoporous silica (NPS) glass is another class of nanoporous substrates. They can be fabricated with tight control over the optical properties as well as the mechanical properties such as the porosity (linked to the pore size) and thickness [93]- [95]. They have been used to create substrates for recording holograms and also for point-of-care diagnosis of non-small cell lung cancer [94], [96].…”

Amphiphilic Polymer Co‐Network: A Versatile Matrix for Tailoring the Photonic Energy Transfer in Wearable Energy Harvesting Devices

“…[ 6 ] Hence, the hosting matrix allows the control of the distance of the donor–acceptor pairs. Currently, several ways exist to fulfill the requirement of putting donors and acceptors in proximity, e.g., direct binding of donor‐acceptor, [ 7 ] direct drop‐casting on a substrate, [ 8 ] loading in mesoporous silica, [ 9 ] or designed diblock copolymer micelles. [ 10 ] Despite the workability of these techniques on investigating energy transfer donor–acceptor pairs under specific conditions, they lack the universality to host all types of luminescent materials and to allow feasible energy transfer routes.…”

“…In addition, with the donor–acceptor pair's proximity provided by the APCN matrix, not only FRET can be easily realized, but also plasmon‐induced resonance energy transfer (PIRET). [ 8b,9a,21 ] When metallic nanoparticles (NPs), e.g., gold (Au) or silver (Ag), are in proximity to luminophores, via the localized‐surface plasmon resonance (LSPR), they increase the excitation rate of single luminophores and their emission intensity. When metallic NPs are in proximity and the absorbance lies in between the donors’ emission and acceptors’ absorption profile, metallic NPs increase the acceptors’ emission (promote the energy transfer efficiency) via increasing the excitation rate of the donor and allowing more energy transfer channels, for instance, increase the FRET radius.…”

Cu2-xS/PbS Core/Shell Nanocrystals with Improved Chemical Stability

“…The relatively recent discovery of doped plasmonic nanocrystals with tunable resonances in the infrared allows for exciton–plasmon coupling in infrared colloidal nanocrystal systems. In particular, copper chalcogenide nanocrystals are doped plasmonic nanocrystals with hole concentrations tuned by the number of copper vacancies. − Litvin et al have combined Cu 2‑ x Se and PbS nanocrystals in a nanoporous silicate matrix and as stacked films separated with a polymer, and they suggest that an enhancement of photoluminescence is possible. However, the structural disorder in their mixtures of nanocrystals precludes measurements of the separation distance between the PbS and the Cu 2‑ x Se and thus a quantitative understanding of exciton–plasmon coupling.…”