Chakravarthy Venkateswaran

The effect of manganese (Mn) substitution on the B site of the ferroelectric bismuth potassium titanate ceramic has been investigated. Samples of Bi _0.5 K _0.5 Ti _{1− x} Mn _x O ₃ ( x = 0, 0.01, 0.03, and 0.05) were prepared by ball mill‐assisted solid state reaction of the stoichiometric oxides. The substitution of Mn into Bi _0.5 K _0.5 TiO ₃ (BKT) is confirmed by characteristic X‐ray diffraction and Raman peaks; phase purity increases due to the reduction in secondary phases upon Mn doping. The surface adsorbed oxygen species decreases with increasing Mn content. The 1% Mn‐doped sample shows the highest polarisation ( P _max ) and remanent polarisation ( P _r ) among the samples. Further increasing Mn concentration results in high leakage current and reduced ferroelectric properties.

Gas sensors are widely used in industrial, medical, and environmental applications for monitoring and quantifying gas molecules under ambient conditions. However, the absence of a dedicated characterization/testing setup limits comprehensive evaluation and development of gas sensors. This work presents the development of a cost-effective and multifunctional gas sensor testing setup using an operational amplifier-based electrical interfacing circuit, a multifunctional data acquisition card, a syringe pump, and a LabVIEW-based control program. Initial system calibration done using standard known resistors (±1% tolerance) confirmed the setup’s accuracy, with results closely matching those obtained from a Keithley DMM 2700, validating its reliability. The developed setup was tested with variable volatile organic compound (VOC) concentrations with controlled thermal conditions and fixed bias voltage operation to enable precise evaluation of gas sensors. To demonstrate its sensor characterization capability, three sensors using p- and n-type semiconductors were deposited on the fabricated interdigitated electrodes. P-type sensor 1 and n-type sensor 2 evaluated V–I responses under varying VOC concentrations, revealing conductivity changes. Sensor 2 assessed thermal stability, showing staircase heating with minimal fluctuations. P-type sensor 3 examined time-dependent responses to ethanol, acetone, and toluene at room temperature, 50, and 100 °C under a fixed bias, confirming the expected semiconducting behavior of the sensing material. These results demonstrate the VOC sensor testing setup as a robust platform for comprehensive gas-sensor characterization, enabling deeper insights into sensor behavior and advancing next-generation devices.

Conventional techniques for identifying heavy metal ions in water are laborious and time-consuming. Therefore, it is necessary to create innovative sensing technologies that can detect with greater sensitivity and speed. Although there have been reports of optical-based assays utilising fluorescent nanomaterials, these assays usually rely on variations in signal strength. However, this approach has significant drawbacks when it comes to environmental monitoring. Fluorescence carbon dots (CDs) have been prepared by facile synthesis from Blood berries. A homemade heavy metal optical detector is constructed to accurately identify heavy metal ions, exclusively Cr⁶⁺ ions in a water medium. Their optical emission signature varies based on the specific chromium ions in solution, and the emission intensity also changes depending on its concentration. The quenching behaviour is attributed to the interaction between the metallic cations and the fluorescent surface states of the carbon dots. Another application is the encapsulation of CDs in PVDF polymer to form a flexible film and use it as a phosphor for LED conversion.