The present work reported the polyaniline (PANI) and multiwalled carbon nanotube (MWCNT)-based nanocomposite as a sensing material for the determination of aqueous ammonia by the enhanced fluorescence method. The excitation wavelength-dependent photoluminescence (PL) intensity has shown dual emission peaks at 340 and 380 nm that correspond to two different excitation energy states. The pH-based PL intensity and zeta potential variation were analyzed to optimize the suitable medium for aqueous ammonia sensing. Zeta potential was found to shift from 4 to −21 mV upon changing the pH of the the solution from acidic to alkaline medium. The fluorescence intensity of PANI/MWCNTs was found to increase upon increasing the pH from 3.0 to 6.0 (acidic region) and exhibits a plateau upon further increasing the pH from 7.0 to 12 (basic region). The PANI/MWCNT composite has shown a linear response to aqueous ammonia concentration varying from 25 to 200 μM with a correlation coefficient (R 2) of 0.99 and a limit of detection of 15.19 μM. The presence of relevant interference molecules and physiological ions had no influence on the detection of aqueous ammonia. Field-level study demonstrated that the level of aqueous ammonia can be determined selectively by using the PANI/MWCNT composite for various applications. The mechanism for the selective detection of aqueous ammonia is deliberated in detail.

In this paper, we reported the controlled synthesis of tungsten disulfide/reduced tungsten oxide (WS 2 /W 18 O 49 ) heterojunctions for highly efficient room temperature NO x and ammonia (NH 3 ) sensors. X-ray diffraction analysis revealed the formation of the oxygen-deficient W 18 O 49 phase along with WS 2 . Field-emission scanning electron microscopy and transmission electron microscopy displayed the formation of WS 2 flakes over W 18 O 49 nanorods. X-ray photoelectron spectroscopy showed the presence of tungsten in W 4+ , W 5+ , and W 6+ oxidation states corresponding to WS 2 and W 18 O 49 , respectively. The WS 2 /W 18 O 49 heterojunction sensor exhibited sub-ppm level sensitivity to NO x and NH 3 at room temperature. The heterojunction sensor detected 0.6 ppm NO x and 0.5 ppm NH 3 , with a corresponding response of 7.1 and 3.8%, respectively. The limit of detection of the sensor was calculated to be 0.05 and 0.17 ppm for NH 3 and NO x , respectively. The cyclic stability test showed that the sensor exhibited high stability even after 24 cycles for the detection of NH 3 and 14 cycles for NO x . Compared to pristine WO 3 and WS 2 , the WS 2 / W 18 O 49 heterojunction showed high selectivity toward NO x and NH 3 . The results could be useful for the development of room temperature NO x and NH 3 sensors.

In this modern world, achieving high level security is a critical task. There are many authentication techniques have been improved and comparatively forging techniques also developed. So we are in the need of promising authentication methods by considering more security, reliability, cost effectiveness, easier implementation etc. Authentication includes identification, verification and recognition. It can be achieved using a biometric system which uses human physiological features such as fingerprint, palm print, iris, voice and facial recognitions. All such systems having the chances of threaten easily. To overcome this, advanced finger vein recognition technique is proposed and implemented in real time which is unique, does not need any physical contact, invisible feature, non-invasive, hard to be cloned, provide high accuracy and security using NIR (Near Infra-Red) scanning and advanced image processing technology embedded with PIC16F877A microcontroller. The proposed system can be used anywhere to prevent the unauthorized access and protects the privacy information. It can be extensively implemented in ATM's (Automatic Teller Machines), banking sectors, money transfer systems, military areas, hospitals, entry control etc.

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