Pradyumna Mulpur

Flexible Ag–C60 nano-biosensors based on surface plasmon coupled emission for clinical and forensic applications

The relatively low sensitivity of fluorescence detection schemes, which are mainly limited by the isotropic nature of fluorophore emission, can be overcome by utilizing surface plasmon coupled emission (SPCE). In this study, we demonstrate directional emission from fluorophores on flexible Ag-C60 SPCE sensor platforms for point-of-care sensing, in healthcare and forensic sensing scenarios, with at least 10 times higher sensitivity than traditional fluorescence sensing schemes. Adopting the highly sensitive Ag-C60 SPCE platform based on glass and novel low-cost flexible substrates, we report the unambiguous detection of acid-fast Mycobacterium tuberculosis (Mtb) bacteria at densities as low as 20 Mtb mm(-2); from non-acid-fast bacteria (e.g., E. coli and S. aureus), and the specific on-site detection of acid-fast sperm cells in human semen samples. In combination with the directional emission and high-sensitivity of SPCE platforms, we also demonstrate the utility of smartphones that can replace expensive and cumbersome detectors to enable rapid hand-held detection of analytes in resource-limited settings; a much needed critical advance to biosensors, for developing countries.

One-Step Synthesis of Colloidal Quantum Dots of Iron Selenide Exhibiting Narrow Range Fluorescence in the Green Region

The instantaneous isolation of green fluorescent colloidal quantum dots of iron selenide capped with biocompatible oleic acid is reported in this study. These iron-containing quantum dots also serve as a safe alternative to the conventionally used metal-chalcogenide systems in which the heavy metal component is usually toxic. The isolated colored colloidal solutions exhibited intense green fluorescence on exposure to ultraviolet light, which was also confirmed by photoluminescence spectroscopy. The isolated product was subjected to dynamic light scattering and transmission electron microscopy, and the particles were found to exhibit spherical morphology with an average diameter of 6–8 nm, confirming the isolation of quantum dots. The isolated iron selenide quantum dots have promising potential towards bioimaging and sensing, due to the biocompatible coating of oleic acid and iron, which also allows possibility of further chemical derivatization.

Carbon nanotubes as novel spacer materials on silver thin-films for generating superior fluorescence enhancements via surface plasmon coupled emission

In this study, we report the first time implementation of single/multi-walled carbon nanotubes, as novel spacer materials, on a silver (Ag) thin-film based surface plasmon coupled emission (SPCE) platform. The engineered Ag-CNT SPCE substrates enabled the realization of up to ~10-fold enhancement in fluorescence signal intensity, of the rhodamine b dye. This study addresses the issue that, while many of the biochemical sensing strategies are based on fluorescence, they are all fundamentally limited by the isotropic nature of the phenomenon that results in low signal collection efficiency ( 50% signal collection efficiency. Considering the easy functionalization of these carbon nano-allotropes, and their high sensitivity; the economical Ag-CNT SPCE platforms can be effectively extended towards sensing applications.

Surface plasmon coupled emission as a novel analytical platform for the sensitive detection of cysteine

Abstract Thiolated amino acids are biologically important molecules due to their role in protein folding and structure. One such molecule is cysteine (Cys), which acts as a biomarker for diseases like cancer, HIV, sepsis, etc., making its rapid detection imperative and essential. In this study, we report the sensitive detection of the thiolated amino acid Cys, from the non-thiolated amino acid arginine (Arg), using the novel surface plasmon coupled emission (SPCE) platform, characterized with high signal-to-noise ratios. Our studies were performed on the conventional silver (Ag) SPCE substrate, where Cys was detected to a nanomolar level, which is a major improvement to the previously reported level of sensitivity. This can be attributed to the highly sensitive SPCE platform and the unique thiol-Ag interactions associated specifically with Cys. We have also shown the role and influence of the coating process on sensitivity of detection and substantiated the advantages of SPCE over the SPR-based strategy of detection. The simplistic and economical SPCE platform enabled the sensitive detection of Cys that is of biological and medical relevance.

Surface plasmon coupled emission studies on engineered thin film hybrids of nano α−Al2O3 on silver

We report the first time engineering and fabrication of a novel thin film hybrid of nano α-alumina doped in a polyvinyl alcohol (PVA) matrix along with rhodamine b (Rh.B) on a silver thin film. Silver films of 50 nm thickness on glass slides were fabricated by thermal evaporation. Nano α-alumina was synthesized through the combustion route and characterized by XRD. The α-alumina was dispersed in the PVA-Rh.B matrix by tip sonication. The resultant solution was spin coated on the Ag thin film at 3000 rpm to generate an overcoat of ∼30 nm. We have designed and constructed an opto-mechanical setup for performing the SPCE studies. Excitation with a 532 nm continuous laser, led to the coupling of the energy of Rh.B emission to the surface plasmon modes of silver. The emission @ 580 nm was recorded using an Ocean Optics{copyright, serif} fiber optic spectrometer. Calculation of the ratio of signal intensity between the directional SPCE and isotropic fluorescence gives us the factor of signal enhancements which ...