Efficiency enhancement in dye-sensitized solar cells using the shape/size-dependent plasmonic nanocomposite photoanodes incorporating silver nanoplates

Double detection of mycotoxins based on aptamer induced Fe3O4@TiO2@Ag Core - Shell nanoparticles "turn on" fluorescence resonance energy transfer

Multiple and sensitive mycotoxin detection is an essential early-warning mechanism for safeguarding human health, and preserving the environment. We synthesized a turn-on Fluorescence Resonance Energy Transfer (FRET) aptamer sensor based on the unique fluorescence quenching and substrate recognition characteristics of Ag NTs (energy receptors) and aptamer modified Fe3O4@TiO2 NP (energy donor) to detect multiple toxins using a single diagnostic approach. The addition of aflatoxin B1 (AFB1) and ochratoxin A (OTA) resulted in a change in fluorescence intensity at 510 and 650 nm, which can be employed for simultaneous recognition with detection limits of 0.94 ng·mL-1 (R2 = 0.997) and 0.54 ng·mL-1 (R2 = 0.995). The aptasensors have been successfully applied for the determination of AFB1 and OTA in grain and oil samples with high recovery rates. The approach provides novel possibilities for the development of sensitive and selective aptasensors with potential applications in aptamer-recognized multifunctional biosensing.

Metallic nanoparticles and hybrids of metallic nanoparticles/graphene nanomaterials for enhanced photon harvesting and charge transport in polymer and dye sensitized solar cells

Solar energy is a sustainable option in the provision of affordable and clean energy. Conversion of solar energy to electricity requires the development of materials and technologies that are not only efficient but also cost-effective. Polymer solar cells (PSCs) and dye sensitized solar cells (DSSCs) are some of the cost-effective technologies for solar energy conversion. However, PSCs suffer from poor optical absorption and charge carrier mobility, while the major drawback to high efficiencies in DSSCs is charge carrier recombination. This article examines the potency of plasmonic metallic nanoparticles (MNPs) and hybrids of MNPs/graphene nanomaterials (GNMs) in mitigating these challenges. MNPs and MNPs/GNMs incorporated in these devices enhance light harvesting to extended wavelengths and improve charge transport. MNPs in the photoanode of DSSCs serve as cosensitizers to offer complementary optical absorption, while MNPs/GNMs as counter electrode yield high catalytic activity comparable to Pt. Simultaneous application of MNPs and/or MNPs/GNMs in PSCs' interfacial and active layers yield enhanced broadband optical absorption and effective charge transport. The mechanisms by which these nanomaterials enhance light harvesting in these devices are discussed in detail. The material characteristics that influence the performance of MNPs and MNPs/GNMs modified devices, such as MNPs size, shape, and morphology, are highlighted. Hence, this article presents perspectives and strategies on successful utilization of plasmonic MNPs and hybrids of MNPs/GNMs to mitigate the challenges of poor optical absorption and charge transport of PSCs and DSSCs for high efficiencies.

Enhanced Absorption Performance of Dye-Sensitized Solar Cell with Composite Materials and Bilayer Structure of Nanorods and Nanospheres

The concept of localized surface plasmon resonance has been applied to increase the absorption efficiency of dye-sensitive solar cells (DSSCs) by using various photoanode structures. A three-dimensional model for a photoanode of the DSSC based on composite materials was developed using COMSOL Multiphysics. Spherical-, rod- and triangular-shaped aluminum nanoparticles were employed in the core of SiO2 to examine the influence of morphology on the performance of DSSCs in the 350–750 nm wavelength range. The UV-Vis absorption results indicated that aluminum nanoparticles with spherical, rod and triangle morphologies had 39.5%, 36.1% and 34.6% greater absorption capability than aluminum-free nanoparticles. In addition, we investigated the effect of plasmonic absorption in DSSCs for photoanodes made of TiO2, SiO2 and bilayer TiO2/SiO2 with and without covering aluminum nanoparticles. The TiO2 and SiO2 nanoparticles had fixed diameters of 90 nm each. The UV-Vis absorption and Tauc curves indicated that the TiO2/SiO2 bilayer structure (with and without aluminum nanoparticles) had greater absorption and lower bandgap energies than individual TiO2 and SiO2 nanoparticles. Furthermore, bilayer photoanode nanostructures were investigated based on nanospheres and nanorods for core–shell Al@SiO2 nanoparticles. The results indicated that a photoanode with nanorod/nanosphere structure had a 12% better absorption capability than a nanosphere/nanorod configuration. This improvement in absorption is attributed to the high surface area, which boosts dye loading capacity and long-term light capture, resulting in greater interaction between the dye and the photon. Our study develops core–shell nanoparticles with optimized shape and materials for bilayer photoanode structures in photovoltaic technology.

Broadband Plasmonic Enhancement of High-Efficiency Dye-Sensitized Solar Cells by Incorporating Au@Ag@SiO2 Core-Shell Nanocuboids

The introduction of plasmonic additives is a promising approach to boost the efficiency of the dye-sensitized solar cell (DSSC) since they may improve the light harvesting of a solar cell. Herein, we design broadband and strong plasmonic absorption Au@Ag@SiO₂ nanocuboids (GSS NCs) as nanophotonic inclusions to achieve plasmon-enhanced DSSCs. These multiple-resonance absorptions arising from GSS NCs can be readily adjusted by altering their structures to complementarily match the absorption spectra of the dyes, especially in weak absorption zones. By subtly regulating the position of nanophotonic inclusions in the photoanodes, not only the plasmonic near-field enhancement but also far-field light scattering could be adequately developed to promote the light harvest and thus the efficiency of DSSCs. The resulting solar cells yield an average efficiency of 10.34%, with a champion value of 10.58%. The electromagnetic simulations are consistent with the experimental observations, further corroborating the synergistic effect of plasmonic improvement in these DSSCs.

Local symmetry breaking in SnO2 nanocrystals with cobalt doping and its effect on optical properties

X-ray photoemission spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to study the structural and morphological characteristics of cobalt doped tin(iv) oxide (Sn1-xCoxO2; 0 ≤ x ≤ 0.04) nanocrystals synthesized by a chemical co-precipitation technique. Electronic structure analysis using X-ray photoemission spectroscopy (XPS) shows the formation of tin interstitials (Sni) and reduction of oxygen vacancies (VO) in the host lattice on Co doping and that the doped Co exists in mixed valence states of +2 and +3. Using XRD, the preferential position of the Sni and doped Co in the unit cell of the nanocrystals have been estimated. Rietveld refinement of XRD data shows that samples are of single phase and variation of lattice constants follows Vegard's law. XRD and TEM measurements show that the crystallite size of the nanocrystals decrease with increase in Co doping concentration. SAED patterns confirm the monocrystalline nature of the samples. The study of the lattice dynamics using Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy shows the existence of many disorder activated forbidden optical phonon modes, along with the corresponding classical modes, signifying Co induced local symmetry breaking in the nanocrystals. UV-Vis spectroscopy shows that the optical band gap has red shifted with increase in doping concentration. The study of Urbach energy confirms the increase in disorder in the nanocrystals with Co doping. Local symmetry breaking induced UV emission along with violet, blue and green luminescence has been observed from the PL study. The spectral contribution of UV emission decreases and green luminescence increases with increase in doping. Using PL, in conjunction with Raman spectroscopy, the type of oxygen vacancy induced in the nanocrystals on Co doping has been confirmed and the position of the defect levels in the forbidden zone (w.r.t. the optical band gap) has been studied.

Microwave-solvothermal synthesis of various TiO2 nano-morphologies with enhanced efficiency by incorporating Ni nanoparticles in an electrolyte for dye-sensitized solar cells

A novel systematic approach is demonstrated to enhance the efficiency of dye-sensitized solar cells by impregnating Ni-nanoparticles into I⁻/I₃⁻ electrolyte with various TiO₂ nanomorphologies-based photo-anodes synthesized via microwave-solvothermal process.