The possibility of using novel architectures based on carbon nanotubes (CNTs) for a realistic monitoring of the air quality in an urban environment requires the capability to monitor concentrations of polluting gases in the low-ppb range. This limit has been so far virtually neglected, as most of the testing of new ammonia gas sensor devices based on CNTs is carried out above the ppm limit. In this paper, we present single-wall carbon nanotube (SWCNT) chemiresistor gas sensors operating at room temperature, displaying an enhanced sensitivity to NH3. Ammonia concentrations in air as low as 20 ppb have been measured, and a detection limit of 3 ppb is demonstrated, which is in the full range of the average NH3 concentration in an urban environment and well below the sensitivities so far reported for pristine, non-functionalized SWCNTs operating at room temperature. In addition to careful preparation of the SWCNT layers, through sonication and dielectrophoresis that improved the quality of the CNT bundle layers, the low-ppb limit is also attained by revealing and properly tracking a fast dynamics channel in the desorption process of the polluting gas molecules.

A sensor array based on heterojunctions between semiconducting organic layers and single walled carbon nanotube (SWCNT) films was produced to explore applications in breathomics, the molecular analysis of exhaled breath. The array was exposed to gas/volatiles relevant to specific diseases (ammonia, ethanol, acetone, 2-propanol, sodium hypochlorite, benzene, hydrogen sulfide, and nitrogen dioxide). Then, to evaluate its capability to operate with real relevant biological samples the array was exposed to human breath exhaled from healthy subjects. Finally, to provide a proof of concept of its diagnostic potential, the array was exposed to exhaled breath samples collected from subjects with chronic obstructive pulmonary disease (COPD), an airway chronic inflammatory disease not yet investigated with CNT-based sensor arrays, and the results were compared to those from of healthy subjects breathprints. Principal component analysis showed that the sensor array was able to detect various target gas/volatiles with a clear fingerprint on a 2D subspace, was suitable for breath profiling in exhaled human breath, and was able to distinguish subjects with COPD from healthy subjects based on their breathprints. This classification ability was further improved by selecting the most responsive sensors to nitrogen dioxide, which has been proposed as a biomarker of COPD.

In modern days, self‐assembled monolayer (SAM) functionalized surfaces represent an interesting tool for the development of ultrasensitive and selective sensing platforms for the detection of chemical substances such as biomolecules and gases. The ability of SAM to generate different functional groups on a single surface such as zinc oxide (ZnO) can be used to immobilize biomolecules and detect different analytes such as gases, proteins, etc. Herein, SAM functionalized ZnO NW‐based sensors are developed for acetone exhaled breath analysis. ZnO NWs are synthesized using a vapor–liquid–solid mechanism and their functionalization is done with two different SAMs, i.e., (3‐aminopropyl)trimethoxysilane (APTMS) and 3‐glycidoxypropyltrimethoxysilane (GLYMO). The enhancement in the electron depletion layer resistance (and also width) due to the capturing of electrons from the ZnO NWs surface by APTMS and GLYMO molecules is found to be the major reason in their superior sensing performances. The amine (–NH2) groups of APTMS monolayer enhance the sensors selectivity toward acetone due to their reactions with acetone molecules, which produce imine in addition to water molecules. Moreover, after the functionalization with APTMS SAMs, the detection limits of the sensors are improved from 6 to 0.5 ppm, which makes these devices potential candidates for acetone exhaled breath analysis.

Experimental evidence of differences in the electronic properties of an insulating and a conducting SrTiO3/LaAlO3 interface is provided by soft x-ray spectroscopies. While core level photoemission measurements show that only at the conducting interface Ti ions with 3+ ionization state are present, by using resonant photoemission and x-ray absorption spectroscopies, it is shown that in both samples in-gap states with a Ti 3d character are present, but their density is higher at the conducting interface.

A novel air-stable Sn-based hybrid perovskite system, MA1−xDMAxSnBr3, system is provided.

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A set of LaAlO3/SrT iO3 (LAO-STO) interfaces has been probed by x-ray photoemission spectroscopy in order to contrast and compare the effects of LAO overlayer thickness and of the growth conditions on the electronic properties of these heterostructures. These effects are tracked by considering the band-offset and the density of Ti +3 states, respectively. It is shown that the dominant effects on the local electronic properties are determined by the O2 partial pressure during the growth. In particular, a low P(O2) yields Ti +3 states with higher density and lower binding energy as compared to the sample grown at high P(O2) or to the bare STO reference sample. Band offset effects are all below about 0.7 eV, but a careful analysis of Ti 2p and Sr 3d peaks shows that valence band offsets can be at the origin of the observed peak width. In particular, the largest offset is shown by the conducting sample, that displays the largest Ti 2p and Sr 3d peak widths.