Whispering Gallery Mode Assisted Enhancement in the Power Conversion Efficiency of DSSC and QDSSC Devices Using TiO₂ Microsphere Photoanodes

Mesoporous TiO₂ nanoparticles are excellent photoanodes for sensitized solar cells (SSC). However, a significant loss in the photoconversion efficiency (PCE) occurs due to the inefficient light absorption. Large Mie scattering from mesoporous micron-sized spheres could be used to enhance the absorption and hence the PCE. Here, we show that a composite comprising a TiO₂ mesoporous microsphere with smooth surface (SμS-TiO₂) exhibiting whispering gallery modes (WGM) and a commercial TiO₂ mesoporous nanoparticle (Degussa P25) with an optimum ratio (80:20 wt %) shows significant enhancement in PCE of DSSC and QDSSC devices. SμS-TiO₂ exhibits strong WGM as evidenced from the photoluminescence studies carried out using a laser with an excitation wavelength λ_exc = 325 nm. These microspheres sensitized with N719 dye or CdSe/CuInS₂ QDs are shown to exhibit emission characteristics strongly coupled to WGM resulting in an enhanced PCE in SSC. Increases in PCE of ∼24% in DSSC devices and 80–95% in QDSSC devices of 0.25 cm² area are demonstrated. Thus, TiO₂ composite exhibiting WGM can be used as a generic photoanode to achieve maximum PCE for Grätzel type sensitized solar cells. This study suggests special class of solar cells called “whisperonic solar cells”

Peptide-Based Polymer–Polyoxometalate Supramolecular Structure with a Differed Antimicrobial Mechanism

Because of the increasing prevalence of multidrug resistance feature, several investigations have been so far reported regarding the antibiotic alternative supramolecular bioactive agents made of hybrid assemblies. In this regard, it is well-established that combinational therapy inherited by assembled supramolecular structures can improve the bioactivity to some extent, but their mode of action has not been studied in detail. We provide first direct evidence that the improved mechanism of action of antimicrobial supra-amphiphilic nanocomposites differs largely from their parent antimicrobial peptide-based polymers. For the construction of a hybrid combinational system, we have synthesized side-chain peptide-based antimicrobial polymers via RAFT polymerization and exploited their cationic nature to decorate supra-amphiphilic nanocomposites via interaction with anionic polyoxometalates. Because of cooperative antimicrobial properties of both the polymer and polyoxometalate, the nanocomposites show an enhanced antimicrobial activity with a different antimicrobial mechanism. The cationic stimuli-responsive peptide-based polymers attack bacteria via membrane disruption mechanism, whereas free radical-mediated cell damage is the likely mechanism of polymer–polyoxometalate-based supra-amphiphilic nanocomposites. Thus, our study highlights the different antimicrobial mechanism of combinational systems in detail, which improves our understanding of enhanced antimicrobial efficacy