Tailoring the selectivity of ultralow-power heterojunction gas sensors by noble metal nanoparticle functionalization

Abstract

Heterojunctions are used in solar cells and optoelectronics applications owing to their excellent electrical and structural properties. Recently, these energy-efficient systems have also been employed as sensors to distinguish between individual gases within mixtures. Through a simple and versatile functionalization approach using noble metal nanoparticles, the sensing properties of heterojunctions can be controlled at the nanoscopic scale. This work reports the nanoparticle surface functionalization of the TiO2/CuO/Cu2O mixed oxide heterostructures, where the gas sensing selectivity of the material is tuned to achieve versatile sensors with ultra-low power consumption. Functionalization with Ag or AgPt-nanoclusters (5-15 nm diameter), changed the selectivity from ethanol to butanol vapour. The Pdnanocluster functionalization shifts the selectivity from the alcohols to hydrogen. The fabricated sensors show excellent low power consumption below 1 nW. To gain insight into the selectivity mechanism, density functional theory (DFT) calculations were carried out to simulate the adsorption of H2, C2H5OH and n-C4H9OH at the noble metal nanoparticle decorated ternary heterostructure interface. These calculations also show a decrease in the work function by ~2.6 eV with respect to the pristine ternary heterojunctions. This work lays the foundation for the production of a very versatile array of sensors of ultra-low power consumption with applications for the detection of individual gases in a mixture.

Fabrication of AgCu/TiO2 nanoparticle-based sensors for selective detection of xylene vapor

“…Functionalization with Pd-nanocluster, selectivity shifted from alcohols to hydrogen, leading to an exceptionally low power consumption. [11] Wang et al [13] synthesized CoTiO 3 /TiO 2 and Pd-doped CoTiO 3 /TiO 2 (Pd-CTT) nanocomposite using a hydrothermal approach. Their Pd-CTT-based sensor demonstrated a superior response towards 50 ppm benzene and a low limit of detection, which was around 100 ppb levels at 25 C. Such excellent performance towards benzene vapour was associated to the catalytic influence of Pd and creation of p-n CoTiO 3 /TiO 2 heterojunction.…”

“…[20] Therefore, appropriate, and selective detection of BTEX vapours, predominantly at minimal concentrations, is very vital, efficient farming with capable conveyance and Page5 storage may be realized. Though several studies exist on the loading of noble metals on various SMOs [1,[6][7][8][9][10][11][12][13][14][15] , however, to the best of our information, no study has been conducted on the gas sensing properties of TiO 2 nanoparticles loaded with AgCu nanoparticles. In the current work, we show that a higher loading of both Ag/Cu switches the conductivity of TiO 2 from p-type to n-type, where such switching is not temperature or gas dependent.…”

“…Studies have shown that heterojunctions between various SMO nanostructures, particularly those derived from ultrathin films with mixed phases, enhance the sensing response. Thus, Lupan et al 11,12 demonstrated a novel approach for controlling the sensing properties of TiO 2 /CuO/Cu 2 O mixed oxide heterostructure based sensors. Functionalization with Pd-nanoclusters, selectivity shifted from alcohols to hydrogen, led to an exceptionally low power consumption.…”

Catalytic formation of oxalic acid on the partially oxidised greigite Fe3S4(001) surface

“…The D2 semiempirical method of Grimme was included in our calculations to correct the long-range dispersion interactions, 75 which is particularly important for an appropriate description of materials and interface properties. 59,68,[76][77][78][79][80][81][82][83][84][85] periodic plane-wave basis set with an upper kinetic energy threshold fixed at 400 eV was employed to expand the Kohn-Sham valence states. The electronic ground state was determined using a preconditioned conjugate gradients minimisation algorithm, which optimises completely and self-consistently the total (free) energy, which is the variational quantity within this methodology.…”

Inkjet‐Printed rGO/binary Metal Oxide Sensor for Predictive Gas Sensing in a Mixed Environment

“…These can be broadly classified into two groups: i) introduction of molecular sieves with functional porous nano materials, such as metal-organic frameworks, to prevent physical contact with interrupting gas molecules [14,15] and ii) surface functionalization with the incorporation of noble metal particles to maximize the chemical catalytic effect for the target gas species. [16,17] Nevertheless, those efforts have remained insufficient to overcome the fundamental limitation of distinguishing the sensor response to target gases in a mixed environment. Along these lines, an artificial intelligence-based statistical data analysis can be adopted to exploit the regularities and differences in sensor responses that are difficult for humans to perceive from a large amount of characteristic parameter data.…”