This paper presents a flexible and reliable chemiresistor-type NO 2 gas sensor based on single-walled carbon nanotubes (SWNTs) on polytetrafluoroethylene (PTFE) membrane filter substrates. The sensor is realized by using a cost-effective spray coating in the preparation of SWNTs thin film, followed by the fabrication of metal contacts using a shadow mask and polyethyleneimine (PEI) noncovalent functionalization of the SWNTs. This showed a high sensitivity to NO 2 gas at room temperature in dry air; 21.58% to 167.7% for concentrations of 0.75 ppm to 5 ppm, and was almost nonsensitive to ammonia. Gas sensing characterization results, obtained for various substrate bending/wrapping over different cylinders with diameters of 75 mm, 12.5 mm, and 6 mm showed that bending does not significantly affect sensitivity for NO 2 concentrations of 0.75 ppm to 2 ppm, while in the case of 3 ppm to 5 ppm NO 2 , the bent samples indicate enhanced sensitivity. This is probably because of the porous nature of PTFE substrates; these sensors were 1.5 to 2.7 times more sensitive than those fabricated over silicon substrate for 1 ppm and 5 ppm, respectively. Moreover, the relative humidity of 10% and 30% significantly reduced the sensitivity of the sensors. The presented results could be useful for the future development of flexible electronics/sensors for monitoring outdoor air quality and for the detection of volatile organic compounds.

Phytomedicines have been beneficial to humankind for the treatment of implacable ailments from time immemorial. In this report, we have synthesized a carbon dots as a photomedicine from traditional phytomedicine Andrographis paniculata which is widely spread across Southern and Southeastern Asia. Interestingly, these carbon dots exhibited unique pink fluorescence that is perceptibly distinctive from the previous reports. The inherent properties of carbon dots were characterised using Transmission Electron Microscopy, Fluorescence spectroscopy, Absorption spectroscopy, Fourier transform infrared spectroscopy, Selected area diffraction, X‐Ray Diffraction, and Energy Dispersive X‐ray Spectroscopy. Furthermore, thermal stability of carbon dots was determined using Thermo gravimetric analysis. The carbon dots are fabricated to possess breast cancer cell bioimaging applications apart from anti‐bacterial activities against clinically isolated strains of gram‐positive and gram‐negative bacteria and free radicals sensing and scavenging attributes. These findings establish carbon dots as a potential photomedicine with wide healthcare applications.

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The fabricated VOLETs have a working voltage of less than 5 V with a luminance of 3450 Cd m−2. The charge injection with a gate electric field is mainly governed by the choice of organic materials and rough source electrode.