Thin films of monoclinic nanostructured vanadium dioxide are notoriously difficult to produce in a selective manner. To date, post-annealing, after pulsed laser deposition (PLD), has been used to revert the crystal phase or to remove impurities, and non-glass substrates have been employed, thus reducing the efficacy of the transparency switching. Here, we overcome these limitations in PLD by optimizing a laser-ablation and deposition process through optical imaging of the laser-induced plasma. We report high quality monoclinic rutile-type vanadium dioxide (VO₂) (M1) nanoparticles without post-annealing, and on a glass substrate. Our samples demonstrate a reversible metal-to-insulator transition at ∼43 °C, without any doping, paving the way to switchable transparency in optical materials at room temperature.

Tungsten oxide based gas sensors have attracted a lot of attention in breath acetone analysis due to their potential in clinical diagnosis of diabetes. The major problem with this material in sensor application has been remarkable response to all gases but low selectivity to specific gases. Herein, we report the gas sensing performance of WO₃ materials which were synthesized by varying water and ethanol ratios using a facile solvothermal method for acetone detection. The gas sensing properties of as-prepared WO₃ were tested on acetone C₇H₈, NO₂, NH₃, H₂S and CH₄ under relative humidity. X-ray diffraction patterns show that as-prepared WO₃ samples are mainly composed of monoclinic WO₃, a phase having relatively high selectivity to acetone. The as-prepared WO₃ sensors produced using 51:49 ratio of water: ethanol show an increase in acetone response as the acetone concentration increases and a decrease in acetone response as the relative humidity increases. The sensor responded to a very low acetone concentration ranging from 0.5 to 4.5 ppm which is normally found in human breath. Furthermore, the sensor exhibited high sensitivity and selectivity to low ppm of acetone at 100 °C. On contrary, the sensor showed significantly lower response to other gases tested.

This chapter reports on the various methods of fabricating and manufacturing micro and nano sensor, membrane and energy devices. Firstly, the characteristic often sought after by scientists and engineers for effective and efficient performance of these technologies were thoroughly discussed in details together with the characterization techniques for evaluating them. Several state-of-the-art fabricating techniques for sensor devices, water and medical based-membranes, solar cells and batteries were also discussed.