High sensitivity formalin detection in aqueous solutions using plasmonic multifunctional metal insulator metal nanoring based optical refractive index sensor platform Ali Khodaie, Yousef Rafighirani, Hamid Heidarzadeh, Javad Javidan, Yesudasu Vasimalla Scientific Reports, 2026 Formalin contamination in water poses major health and environmental risks, requiring rapid and sensitive detection. This study presents a plasmonic optical biosensor refractive index sensor based on a multifunctional metal-insulator-metal (MIM) nanoring structure optimized for formalin detection. The proposed design features nested nanorings with perpendicular arms and a reflective metal layer, enabling strong electromagnetic confinement and multi-resonance operation and multi-resonance operation. Finite-difference time-domain simulations demonstrate four resonance modes with sensitivities of 1289.30, 823.31, 662.71, and 557.62 nm/RIU, and corresponding FOM values up to 13.73 RIU⁻¹. The sensor exhibits a linear spectral shift versus refractive index variation of aqueous formalin (n = 1.3300-1.3600). Electric-field analysis confirms field localization at resonant sites, contributing to enhanced sensing performance. These results demonstrate the potential of the proposed MIM nanoring platform for highly sensitive and compact optical sensing applications, particularly in real-time environmental monitoring of hazardous chemicals.
Spectroscopic investigation of Cd²⁺ detection using an optimized multilayer CdS/CS₂/2D material-based SPR sensor Keerthan Sai Gurramkondu, Sandeep Boddu, Santhosh Chella, Yesudasu Vasimalla, Santosh Kumar Next Nanotechnology, 2026 This paper presents a design and optimization of a multilayer surface plasmon resonance (SPR) biosensor to monitor refractive index variations associated with cadmium (Cd²⁺) ions in aqueous samples. The study examines the thickness of the silver (Ag) plasmonic layer and the effectiveness of changes in refractive index to optimize the sensor performance. The most important key performance parameters, such as sensitivity, figure of merit (FoM), detection accuracy (DA), and resonance stability, were considered. The sensor uses an FK51A prism, cadmium sulfide (CdS), carbon disulfide (CS₂) layers of high dielectric, and the 2D materials. The angular interrogation and transfer matrix method was used to analyze sensor performance at a wavelength of 633 nm for small refractive index variations (1.333–1.334). The optimized design achieved a baseline sensitivity of 256.3 °/RIU and a maximum sensitivity of 384.4 °/RIU, with a figure of merit (FoM) of 92.97 RIU⁻¹ and a penetration depth of 425.13 nm. In practical applications, selective cadmium detection would require appropriate surface functionalization.
Theoretical investigation of an ultrasensitive label-free SPR biosensor based on AgGaS2/Ag/BP/AlSb multi-layered structure for trace-level albumin sensing M. Jagadeeswar Goud, Yesudasu Vasimalla, Santosh Kumar Modern Physics Letters B, 2026 In this paper, we propose an advanced Label-free surface plasmon resonance (SPR) biosensor for ultrasensitive trace-level albumin monitoring in urinary diagnostics. This study uses the Kretschmann configuration-based multi-layered structure with silver gallium sulfide (AgGaS 2 ), silver (Ag), black phosphorus (BP) and aluminium antimonide (AlSb). To analyze the sensor’s performance, the transfer matrix method is used along with the angular interrogation procedure at a wavelength of 633[Formula: see text]nm. Initially, the optimization of Ag thickness and prism are explored by observing a better minimum reflectance and sensitivity performances. Subsequently, the key role of adding the proposed structure in the SPR sensor is shown by comparing the performance of other structures that categorized with the available layers. Furthermore, the performance analysis is executed with different layers’ thicknesses and found that the maximum attained parameters are a sensitivity of 704.7 ∘ /RIU, quality factor of 101.03[Formula: see text] [Formula: see text], detection accuracy of 0.10. Also, the electric field intensity of the proposed sensor is observed with a significant penetration depth of 456.468[Formula: see text]nm. This outperformed proposed sensor has a heavy weightage as compared with existing work in the field of biological and biomedical applications.
Advanced Optical Sensing Techniques for Biomolecular Detection in the Human Body: Principles, Technologies, and Clinical Perspectives Mogal Mahazira Tabassum, Yesudasu Vasimalla, Ragini Singh, Santosh Kumar Chemical Record, 2026 Optical biosensing technologies have become viable platforms for biomolecular detection, providing rapid and sensitive analysis of a wide range of biological targets such as proteins, nucleic acids, and metabolites. The principles, technological advances, and clinical potential of key optical sensing modalities such as surface plasmon resonance (SPR), surface‐enhanced Raman scattering (SERS), fluorescence, and interferometric sensors are critically reviewed. Although these methods have made important breakthroughs in label‐free detection, real‐time monitoring, and dimension reduction, many are limited by the requirement of controlled laboratory environments, complicated instrumentation, and high fabrication costs. The more recent discoveries in nanophotonics, 2D materials, and integration on a microscale have improved signal stability and device portability, which help to narrow the divide between the real‐world implementation of point‐of‐care (PoC) diagnostics. Automated data interpretation and constant healthcare monitoring are further supported by the inclusion of artificial intelligence (AI) and the Internet of Medical Things (IoMT). Instead of an alleged technological revolution, the current review concentrates on the gradual advances in optical biosensing in the path of clinically valid, affordable, and non‐invasive biomolecular diagnostics.
Plasmon-enhanced black phosphorus-ZrO2-TeO2 multilayer SPR biosensor for ultra-sensitive early detection of brain tumors P. J. V. S. Sricharan, Yesudasu Vasimalla, Santosh Kumar Modern Physics Letters B, 2026 In this study, we present a new ultra-high-performance surface plasmon resonance (SPR) biosensor with a multilayer design incorporating black phosphorus (BP), zirconium dioxide (ZrO 2 ), and tellurium dioxide (TeO 2 ) nanomaterials to achieve an optimal solution for detecting brain tumors in their early stages in a precise localization manner. Owing to the unique optical properties of BP, ZrO 2 , and TeO 2 , the proposed biosensor has good sensitivity and selectivity with an impressive sensing range of a large refractive index (RI), continuous range, and constant response of both normal and cancerous brain tissues. The performance indices that the proposed biosensor has attained are a high sensitivity of 414.537[Formula: see text]/RIU, a quality factor (QF) of 177.568 RIU[Formula: see text], and a figure of merit (FoM) of 106.148 RIU[Formula: see text]. This correct resonance behavior and high sensitivity to change in RI validate that the biosensor has high diagnostic potential and accuracy in detecting early-stage brain tumors meticulously and accurately in real time. These values show that the optical performance and the diagnostic accuracy are greatly enhanced compared to traditional SPR biosensors.
