BITS Faculty Publications

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    TiO2-FG-based plasmonic sensor with enhanced figure of merit for sensing applications: A numerical approach
    (Elsevier, 2025-09) Grover, Nitika; Arora, Pankaj
    A refractive index-based surface plasmon resonance sensor using a multilayer heterostructure in the Kretschmann configuration is proposed for the near-infrared region. In the proposed configuration, aluminum is used as a plasmonic metal, titanium dioxide is used as a dielectric layer, and a fluorinated graphene (FG) layer is used as a 2D nanomaterial to enhance the performance parameters. A thorough comparative study is conducted between popularly used titanium compounds: Titanium dioxide (TiO2) and Titanium disilicide (TiSi2). For the proposed SPR sensor, each layer is engineered and optimized on the grounds of linewidth, detection accuracy (DA), and Figure of Merit (FOM), which are the critical performance parameters. To this end, the geometrical parameters are calculated using the transfer matrix method and analyzed meticulously to find the optimum trade-off points. The proposed sensor is numerically tested efficiently to sense different concentrations of hemoglobin in human blood. For the angle interrogation technique at the wavelength of 1550 nm, the sensor provides an enhanced FOM of 462.8 RIU−1 and a DA of 4 degrees−1. Thus, the proposed design opens a broader window for bio-sensing applications because of the advantages TiO2 and FG layers offer in enhancing the sensing parameters.
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    Fabrication of Au decorated MoS2 Langmuir Blodgett film as SERS sensing scaffold for detection of thiram in aqueous solution and in carrot peels
    (Elsevier, 2024-10) Pande, Surojit
    This paper is focused on simple fabrication of robust and reproducible SERS active substrate through self-assembly of gold nanoparticles (AuNps) entrapped in the Langmuir Blodgett (LB) film of MoS2 flakes. The as prepared Au-MoS2 substrate can detect SERS signals of 4-Mercapto Pyridine (4-Mpy) molecules at trace concentrations down to 10-12 M. The substrate has been further employed in detecting thiram (TH) both in aqueous solution and in carrot peels (CPls). The limit of detection (LOD) of TH in aqueous medium and in CPls have been estimated to be ∼ 5.18 and 10.16 pM respectively. We believe that the applicability of this SERS active substrate may be extended in the trace detections of explosives, drugs and in diagnostic applications.
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    Sybil-resilient publisher selection mechanism in blockchain-based mcs systems
    (IEEE, 2025) Bhatia, Ashutosh; Tiwari, Kamlesh
    In Blockchain-based Mobile CrowdSensing (BMCS) systems, publishers (data collectors) can exploit the ability to create multiple blockchain identities, enabling Sybil attacks. Selfish, malicious, and collusive Sybil behaviors undermine both reward and majority-based data validation mechanisms, discouraging honest participation and threatening system integrity. Existing solutions often fail to address these issues, particularly in environments dominated by selfish or malicious publishers. This paper proposes a novel two-phase publisher selection mechanism to mitigate Sybil attacks in BMCS systems. Phase-I employs a modified Proof-of-Stake (PoS) mechanism with carefully calibrated parameters, including staked amount, coinage, reputation, and randomness. The strategic combination of staked amount and coinage increases the difficulty of Sybil attacks as the system scales over time. Phase-II introduces a lightweight, reputation-based Proof-of-Work (PoW) mechanism tailored for Mobile CrowdSensing (MCS) environments, where puzzle difficulty adjusts dynamically based on the publisher's reputation. Reputation and penalization mechanisms are central to the proposed mechanism, ensuring robust prevention of task domination, selfish behavior, and malicious activities while fostering honest participation. Comprehensive on-chain and off-chain simulations demonstrate the proposed mechanism's effectiveness in mitigating Sybil attacks, reducing their impact, and promoting fair participation.
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    Flexible and Wearable Sensors for Health Monitoring Applications
    (CRC Press, 2023) Gupta, Navneet
    Over the past decade, flexible electronics have attracted much interest as conventional semiconductors are not competent to provide new product paradigms. The flexible devices are bendable, stretched, and can be folded without losing functionality. Flexible electronics devices are used in various fields, such as consumer electronics, medical, health care, and security devices, because they are generally lightweight, non-breakable, and involve a relatively simple manufacturing process. The use of wearable electronics for non-invasive real-time health monitoring has also gained popularity. The continuous monitoring of body locomotion, biophysical parameters, and biomarkers is valuable in quantifying human performance and off-site patient care. Flexible electronics provide a natural interaction between the human body and wearable devices because of their high flexibility and conformity. So, in this chapter, we shall discuss the flexible substrate, active material, transduction mechanism, and fabrication processes of different flexible sensors with a special focus on temperature, pressure, and strain sensors.
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    Realization of ppb-level acetone detection using noble metals (Au, Pd, Pt) nanoparticles loaded GO FET sensors with simultaneous back-gate effect
    (Elsevier, 2022-02) Hazra, Arnab
    In the current study, graphene oxide (GO), uniformly loaded with different noble metal nanoparticles (Au, Pd and Pt) were synthesized by spray coating technique and implemented in field effect transistor (FET) sensors. The morphology, structure, composition and electronic properties of the synthesized materials were characterized. The sensing results indicated that the incorporation of noble metals can greatly enhance the VOC sensing properties of a few layers of GO by using their chemical and electrical sensitization effect. At optimized gate potential, GO FET exhibited outstanding sensing properties at low operating temperature i.e. 50 °C. Specifically, the FET sensor based on Pd loaded GO exhibited the highest response, quickest response/recovery (37 s/91 s) characteristics, best selectivity and low operating temperature towards low concentration of acetone. Almost five times higher sensitivity towards acetone (400 ppb) was achieved in Pd/GO as compared to the pure GO channel nanoparticles under a suitable back gate bias.
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    Synthesis and characterization of hybrid NiO/CeO2 p-n heterojunction nanofibers for room temperature ammonia sensing application
    (Elsevier, 2024-08) Hazra, Arnab
    The development of room temperature chemiresistive NH3 gas sensors with superior selectivity and stability is always an uphill task to solve. This work describes the synthesis and characterization of NiO/CeO2 p-n heterojunction nanofiber assembly using a facile electrospinning method. Systematic studies are conducted using SEM, XRD, XPS, and TEM to examine the microstructure and morphology. The electro spun nanofibers offer high surface area of NiO/CeO2 p-n heterojunction composite sensor with an average fiber diameter of ∼125 ± 20 nm, regulated morphology, and interconnectivity through junction formation. Under ambient temperature, the sensing performance for 10–100 ppm NH3 gas is investigated. The increased specific surface areas, formations of multiple NiO/CeO2 bridging point contacts are responsible for the improved gas sensitivity. Experiments reveal that NiO/CeO2 hybrid nanofiber sensor outperforms the pure NiO NF sensor for NH3 sensing, in addition to superior selectivity, good stability and quick response/recovery time. Gas sensors based on NiO/CeO2 are anticipated to become a viable option for the detection of ammonia in breathed gas of sufferers with gastrointestinal or renal disorders in the future due to their flexibility, room temperature operation, and good reaction to ammonia.
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    Cystamine-cobalt complex based fluorescent sensor for detection of NADH and cancer cell imaging
    (Elsevier, 2019-08) Sidhu, Jagpreet Singh
    The pronounced demand of sensing of biological analytes which play a significant role in progress of cancer cells encouraged us to develop a novel chemosensor having high selectivity and sensitivity for NADH. Therefore, imine linked dipodal receptor (L1) was synthesized and its organic nanoparticles (L1-ONP) were prepared using reprecipitation method to enhance their water solubility. These ONPs form a metal complex with Co(II) which was characterized by UV–vis absorption and Fluorescence Spectroscopy. The ONPs show highly sensitive affinity having a low detection limit (LOD) of 16.95 nM for the cobalt ions. The prepared ONPs metal complex exhibits high selectivity and sensitivity to sense the NADH with a very low LOD of 83.89 nM without any interference from other potentially interfering biological molecules. Fluorescence response from NADH was also not affected by pH and UV irradiation. The sensor was also employed for detection of NADH in MCF-7 cells.
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    Sensor tags for wireless body-centric communication: challenges and opportunities
    (IOP, 2022-09) Rano, Dinesh
    Chapter 10 gives a comprehensive overview of the devices and methods required for interfacing sensor tags for wireless body-centric communication (WBAN). The antenna is an integral part of WBAN devices and plays a vital role in establishing a link between a wearable device and a base communication station situated remotely from the body. The patch antennas used in WBAN applications are often limited by their operational bandwidth, size, reduced efficiency, strong coupling with the body, and high specific absorption rate. This chapter highlights the existing challenges and some solutions for designing an antenna for WBAN applications. An in-depth study of one promising solution related to the design of electromagnetic band-gap surfaces for interfacing the wearable devices and base station is included.
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    Achieving Fairness in IEEE 802.11ah Networks for IoT Applications with Different Requirements
    (IEEE, 2019-07) Rajya Lakshmi, L.
    The IEEE 802.11ah standard can provide cost-effective Internet access to a large number of devices in newly evolving Internet-of-Things (IoT) and machine-to-machine (M2M) networks. To handle high collision probability caused by a large number of devices, it adopts a group-based protocol at the MAC layer and divides nodes (or sensors) into a number of groups. The formed groups may not be uniform in terms of data rate requirements, since each group is a combination of sensors with different traffic characteristics. To achieve fair resource utilization across the groups which in turn maximizes the channel utilization, this paper formulates fair grouping in IEEE 802.11ah networks as an optimization problem, and we develop a heuristic method to solve the problem in real-time. In addition, to ensure fair channel utilization by the nodes in each group, a contention window selection and adjustment method is proposed. Results from extensive simulations conducted in a dense IoT network show that the proposed fairness model achieves a superior performance than the existing methods in terms of throughput, packet delay, energy efficiency, and fairness.
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    Fair Scheduling in IEEE 802.11ah Networks for Internet of Things Applications
    (IEEE, 2020-02) Rajya Lakshmi, L.
    The IEEE 802.11ah standard has been developed to provide Internet access to a large number of devices in the Internet of Things (IoT) and machine-to-machine (M2M) networks. To handle contention from a large number of devices and reduce the collision probability, IEEE 802.11ah partitions nodes into groups by adopting a group- based MAC protocol. The formed groups may consist of nodes with different traffic patterns and hence, the data rate requirements of nodes in a group (and consequently the groups themselves) may not be uniform. To maximize the throughput while minimizing unfairness across groups, this paper formulates fair scheduling in IEEE 802.11ah networks as a multi-objective optimization problem. To maintain fairness among the nodes in a group, contention window size selection of nodes is formulated as an integer programming problem. Since it is difficult to solve these problems in real time, heuristic methods are also proposed. Performance of the proposed methods is evaluated in a dense IoT network and compared with the existing methods. As the number of nodes and groups increase, the proposed method consistently shows a superior performance in terms of fairness, throughput, delay, and power consumption, compared to the existing methods.