Sudha Maria Lis Scaria

There is an ever‐increasing demand for miniaturization and portability of reliable sensor platforms for individualized health monitoring in diagnostics. Photonic crystals (PC)‐based frameworks in conjugation with fluorescence techniques efficiently address these requirements on account of their high sensitivity, compactness, and robust integrated features. Here we demonstrate fluorophore emission engineering via Bloch surface waves (BSWs) supported by one‐dimensional PCs. Since brighter emission directly translates to improved detection performance, achieving highly sensitive PC platforms necessitates careful interfacial nano‐engineering. In this context, cryosorets, which are hybrid nano‐assemblies composed of gold nanoparticles (AuNPs) and TiO ₂ nanorods (TiO ₂ NRs), are used to generate three‐dimensional multi‐fold hotspots. When interfaced with a PC, the resulting metallo‐dielectric hybrid yields photonic crystal‐coupled emission (PCCE), mitigating the challenge of fluorescence quenching. The nanoscale gaps between the plasmonic AuNPs, high refractive index (HRI) TiO ₂ NRs, and graphene oxide (GO) hybrid interface generate strong hotspots, augmenting the fluorescence coupling via the underlying BSW. Integrating such sensors onto smartphones and other personalized devices to enable rapid, on‐site sensing of target analytes is need of the hour. The high 1300‐fold PCCE enhancement enables attomolar sensing of rhodamine reporter molecule and is demonstrated here using a smartphone camera as a detector amenable for resource limited settings.

Photonic crystal gratings (PCGs) and photonic crystal Bragg mirrors (PCMs) are widely used to enhance photoluminescence (PL) in fluorescence-based biosensing, yet most implementations either rely on bulky prism coupling or suffer from strong background from uncoupled spontaneous emission, limiting system integration. Here, we experimentally demonstrate an all-dielectric PCG-PCM interface in which a TiO₂ ridge-groove PCG is fabricated atop a TiO₂/SiO₂ Bragg mirror to form a 1.5D photonic crystal (PC). Bound states in the continuum-enabled resonances in the PCG increase PL spectral flux, polarization selectivity, and near-normal outcoupling, while the PCM suppresses broadband background via stopband filtering and improves PL extraction by recycling downward radiation through radiative boundary-condition engineering. Relative to standalone PCGs or PCMs, the interface achieves up to 5.2-fold improvement in signal-to-background ratio, supported by angle-resolved spectroscopy, back-focal-plane imaging, and numerical simulations. This 1.5D PC establishes a scalable, compact route to high-contrast fluorescence readout for next-generation biosensing and bioimaging.

The optimization of BiVO₄-based structures significantly contributes to the development of a global system towards clean, renewable, and sustainable energies. Enhanced photocatalytic performance has been reported for numerous doped BiVO₄ materials. Bi³⁺-based compounds can be easily doped with rare earth (RE³⁺) ions due to their equal valence and similar ionic radius. This means that RE³⁺ ions could be regarded as active co-catalysts and dopants to enhance the photocatalytic activity of BiVO₄. In this study, a simple microwave-assisted approach was used for preparing nanostructured Bi_1−xEu_xVO₄ (x = 0, 0.03, 0.06, 0.09, and 0.12) samples. Microwave heating at 170 °C yields a bright yellow powder after 10 min of radiation. The materials are characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible–near-infrared diffuse reflectance spectroscopy (UV-Vis-NIR DRS), photoluminescence spectroscopy (PL), and micro-Raman techniques. The effects of the different Eu³⁺ ion concentrations incorporated into the BiVO₄ matrix on the formation of the monoclinic scheelite (ms-) or tetragonal zircon-type (tz-) BiVO₄ structure, on the photoluminescent intensity, on the decay dynamics of europium emission, and on photocatalytic efficiency in the degradation of Rhodamine B (RhB) were studied in detail. Additionally, microwave chemistry proved to be beneficial in the synthesis of the tz-BiVO₄ nanostructure and Eu³⁺ ion doping, leading to an enhanced luminescent and photocatalytic performance.

The optimization of BiVO₄-based structures significantly contributes to the development of a global system towards clean, renewable, and sustainable energies. Enhanced photocatalytic performance has been reported for numerous doped BiVO₄ materials. Bi³⁺-based compounds can be easily doped with rare earth (RE³⁺) ions due to their equal valence and similar ionic radius. This means that RE³⁺ ions could be regarded as active co-catalysts and dopants to enhance the photocatalytic activity of BiVO₄. In this study, a simple microwave-assisted approach was used for preparing nanostructured Bi_1-xEu_xVO₄ (x = 0, 0.03, 0.06, 0.09, and 0.12) samples. The materials are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible-near infrared diffuse reflectance spectroscopy (UV-Vis-NIR DRS), photoluminescence spectroscopy (PL), and micro-Raman techniques. Effects of the different Eu³⁺ ion concentrations incorporated into the BiVO₄ matrix on the formation of the monoclinic scheelite or tetragonal zircon-type BiVO₄ structure, on the photoluminescent intensity, on the decay dynamics of europium emission, and photocatalytic efficiency in degradation of Rhodamine B, were studied in detail.

Optical Tamm structures have potential for the development of optoelectronic devices, provided they overcome the challenge of low-quality factor of modes and inherent losses associated with plasmonic metal films. In this work, we present lasing in a super-Tamm structure consisting of a silver thin film deposited on a 4-(dicyanomethylene)-2-methyl-6-(4- dimethylaminostyryl)-H-pyran (DCM) dye-doped polyvinyl alcohol (PVA) spacer layer coated on a SiO₂/TiO₂ one-dimensional photonic crystal with a lasing threshold of ∼0.07 mJ. The spectral line narrowing and threshold characteristics observed in the emission spectrum corroborate the realization of a waveguided super-Tamm laser. The bi-exponential temporal decay profile of the Tamm lasing modes with an average lifetime of 0.52 ± 0.02 ns confirms the Purcell enhancement of radiative intensity of the DCM dye when coupled to the super-Tamm modes.