Hybrid Noble-Metals/Metal-Oxide Bifunctional Nano-Heterostructure Displaying Outperforming Gas-Sensing and Photochromic Performances

Abstract

As nanomaterials are dominating 21st century’s scene, multiple functionality in a single (nano)structure is becoming very appealing. Inspired by the Land of the Rising Sun, we designed a bifunctional (gas-sensor/photochromic) nanomaterial, made with TiO 2 whose surface was simultaneously decorated with copper and silver (the Cu/Ag molar ratio being 3:1). This nanomaterial outperformed previous state-of-the-art TiO 2 -based sensors for the detection of acetone, as well as the Cu–TiO 2 -based photochromic material. It indeed possessed splendid sensitivity toward acetone (detection limit of 100 ppb, 5 times lower than previous state-of-the-art TiO 2 -based acetone sensors), as well as reduced response/recovery times at very low working temperature, 150 °C, for acetone sensing. Still, the same material showed itself to be able to (reversibly) change in color when stimulated by both UV-A and, most remarkably, visible light. Indeed, the visible-light photochromic performance was almost 3 times faster compared to the standard Cu–TiO 2 photochromic material—that is, 4.0 min versus 10.8 min, respectively. It was eventually proposed that the photochromic behavior was triggered by different mechanisms, depending on the light source used.

A Semiconducting Material Exhibiting Visible-Light Promoted Photochromism, Photoluminescent and Photocatalytic Activity

“…Brighter contrasts in STEM-HAADF mode indicate either a higher atomic number and/or a higher thickness. As previous studies have shown that copper does no enter TiO2 lattice, 18,56 the observed variations in intensity are more likely to result from the presence of neodymium. On the other hand, the high crystalline quality of the grains in Nd1Cu1 can be clearly appreciated, as displayed in Figure 1a.…”

“…A protocol described in detail previously was severely followed to ensure comparable data. 18,[54][55][56] The intensity of the radiation reaching the samples was measured with a radiometer (Delta OHM, HD2302.0, IT), and it was estimated to be 5.0 mW.cm −2 in the visible spectral region (> 400 nm, being nil in the UVA). The irradiation times were considered to be consecutive and absolute.…”

Photo-electrochemical properties of CuO–TiO2 heterojunctions for glucose sensing

“…Microstructural features of the specimens were analysed through the whole powder pattern modelling (WPPM) method [28], as implemented in the PM2K software package [29], using the same modelling strategy as in previous reports by the authors [30,31]. Diffuse reflectance (DR) spectroscopy was used to assess the optical properties of the specimens.…”

TiO2 Surface Hybridisation with Noble Metals (Ag and CuxO) for Solar De-NOx and VOC Removal

“…Indeed, Ag-TiO2 had 83.7 wt% anatase, 5.4 wt% rutile and 10.9 wt% brookite; 2Ag-TiO2 had a very close mineralogy, being composed of 83.0 wt% anatase, 4.5 wt% rutile and 12.5 wt% brookite. [59], which eventually culminates in delaying the ART. This is also reflected by a decrease in the mean average diameter of the crystalline domains, see WPPM microstructural information reported in Tables 2-4 Table 2, third column).…”

“…* There were 2285 observations for every refinement; the number of anatase, rutile and brookite reflections was32,31 and 155, respectively. † From[59]; ‡ from[26].Copper modification led to very close results: ART was hindered (though in lesser extent compared to Ag modification), as Cu-TiO2 was composed of 82.2 wt% anatase, 9.0 wt% rutile and 8.8 wt% brookite. 2Cu-TiO2 composition was similar, anatase accounting for 81.4 wt%, rutile being 8.8 wt%, brookite being the remaining wt%, cfTable 1.…”