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Usually, external solutes alter the local structural arrangement of the water hydrogen bond (H-bond) network. However, urea has a negligible effect on the local structure of water, irrespective of its concentration. In this work, we aim to find the microscopic origin of the inertness of urea toward water’s local structure by using theoretical isotope dilute IR spectroscopy. To get a microscopic resolution of different local environments, we investigate frequency distributions, population of structurally different ensembles, H-bond configurations, and H-bond strength. We find that urea has a negligible effect on the vibrational spectroscopic signatures of water. The solvation shell-wise decomposition of frequency distribution further reveals that the urea has almost zero perturbation to the local structure of any of its solvation shells. However, the frequency distribution of waters near the C=O group and NH2 group reveals a non-negligible impact by urea on water. The frequency distribution of the CO-region is red-shifted and narrower than the bulk water response, indicating a stronger H-bond and enhanced structural ordering of the waters in the CO-region; however, an opposite response is observed for the NH-region. The H-bond strength outcome further supplements this finding. We infer that the O-H oscillators in the CO-region and NH-region have non-negligible counteracting perturbation from the urea molecule. Yet, the overall response is free from any such effects. The insignificant populations and counteracting responses of these two ensembles play a major role.

Light-intensity-modulated displacement sensors are extensively used in numerous applications. Such type of sensors operates by utilizing a pair of adjacent optical fiber—one as transmitter and the other one as receiver. Such displacement sensors have the benefits of higher sensitivity and operating range, because they can efficiently collect more light after a reflectance has occurred. In this brief communication, we report all fiber optic displacement sensor using different reflectors such as plane, convex and concave. The experiment has been performed in the context of different refractive index-based solutions along with a comparative sensing analysis of these sensors. The attained results indicate that concave reflector-based displacement sensor yields the maximum sensitivity as compared to the other reflectors. Further, there has been good corroboration between simulated and observed transmittance. The findings is envisioned to help build more inexpensive displacement sensors with augmented sensitivity.

This short communication reports a unique proposition of a versatile sensing scheme—aimed at early detection of oral cancer. Based on intensity modulation, the probe can render both qualitative as well as quantitative assessments via saliva samples. It can further plausibly affirm the stage of oral cancer in the patient. With remarkable response time and superior specificity due to incorporation of biomarkers, this catheter like probe allows user to get rid of sample storage problem and other allied complications.

This paper presents the fabrication of a prototype with unique functionalities for monitoring human heart rate via simple insertion of fingertip on an infrared based sensor. The variation in the absorbance caused by the repeated pumping of oxygenated blood to various tissues within the body leads to distinct peaks and dips corresponding to the signal from the detector. Further, a MATLAB based Graphical User Interface (GUI) is developed to visualize this heart-beat signal as well as count the heart rate. In addition, the oxygen concentration can also be deciphered from the reported sensing scheme. The developed prototype seems to be in excellent match with standard heartrate monitoring device. It is believed that this multimodal prototype will pave way for more investigation towards development of sophisticated AI based analysis.

With the persistent rise of COVID-19 cases, it is imperative to have rapid assessment of infection with minimal logistics. Although different diagnostic techniques for SRAS-CoV-2 are available, there are limitations in terms of turn-around time, sensitivity, and specificity issues. In this direction, this work reports the effective exploitation of fiber optic biosensor especially for in vivo identification of SARS-CoV-2. The proposed catheter like probe is envisioned to alleviate the need for sample storage as well as other allied complicacies. The scheme for qualitative as well as quantitative assessment is elaborately presented here for this portable probe. The proposed probe equipped with rapid diagnosis is believed to have immense potential through adaptive measures.

Arsenic is well known for its toxicity and various health effects. In this work, we report a simple, environment friendly and cost effective colorimetric approach for selective detection of arsenic (III) in aqueous medium. PEG functionalized silver nanoparticles were synthesized by chemical reduction method and applied for detection of heavy metal ions like arsenic(III), cobalt (II), cadmium (II), copper (II), iron (III), lead (II), mercury (II), magnesium (II) and nickel (II). In case of arsenic samples, we have observed perceptible alteration of colors from yellow to bluish due to aggregation of PEG functionalized silver nanoparticles. Absorption spectra of the arsenic samples were measured through UV–Vis spectrometry to derive detectable range of arsenic (III) concentration. The results have showed that the detection limit of this sensing unit is 1 ppb with an excellent linearity of ∼0.99. Keywords: Silver nanoparticles, Polyethylene glycol, Colorimetric, Arsenic (III)