This Thematic Series is an exciting collection of works on functional nanomaterials and their related surface modifications in order to enhance sensing properties. Particular emphasis was placed on rapidly emerging applications in the sector of air-quality monitoring and energy systems for environmental sustainability.
The topics of this Thematic Series, based on 23 peer-reviewed articles, include works on advanced gas sensing semiconducting materials, hybrid materials and nanocomposites for chemical sensing, catalytic sensing materials, metal oxides for chemical sensing and energy applications, carbon-based materials for chemical sensing and energy applications, piezoelectric and thermoelectric materials for energy harvesting applications, new nanotechnology-based sensors for monitoring gaseous and liquid pollutants, surface-sensitive spectroscopy for studying sensor/gas interaction, modelling of materials, devices, sensor systems and energy systems, and functional applications of environmental sensors and energy systems.
Figure 1: SEM image (a) and Raman spectrum (b) of the GO platelets deposited on SiO2/Si wafer.
Figure 2: SEM images of the obtained samples based on graphene and zinc oxide at low (a) and high (b) magnifi...
Figure 3: (a) EDX spectrum and (b) quantitative analysis of the hybrid structure based on GO and ZnO annealed...
Figure 4: Dynamical response of ZnO and RGO–ZnO structures at 250 °C and RH = 50% @ 20 °C: (a) towards 50 and...
Figure 5: Schematic diagram of the sensing mechanism between acetone and the RGO–ZnO structure: Oxygen is abs...
Figure 6: Response of RGO–ZnO and pristine ZnO nanostructures towards 100 ppm acetone and ethanol at a workin...
Figure 7: Calibration curve for acetone at an operating temperature of 250 °C and in a humid air background (...
Figure 1: X-ray diffractograms of Ge:SiO2 thin films deposited at 300, 400 and 500 °C.
Figure 2: HRTEM images of the Ge:SiO2 thin film co-deposited on a Si substrate at 500 °C: (a) corresponding S...
Figure 3: Schematic of sample structure and electrical measurement.
Figure 4: Current density versus voltage characteristics in dark (empty squares) or under integral light (fil...
Figure 5: The charge carriers transport mechanism described schematically.
Figure 6: Current density versus voltage characteristics in dark (empty squares) or under integral light (fil...
Figure 7: Photodetector responsiveness: a) spectral photoresponsivity, for Al/n-Si/Ge:SiO2/ITO and Al/n-Si/SiO...
Figure 8: Photovoltaic response speed of the photodetector structure (fabricated at 400 °C) under pulsed (Pin...
Figure 1: SEM micrograph of as-grown indium oxide nano-octahedra.
Figure 2: XRD patterns of the pure In2O3 octahedra (top) and a commercially available In2O3 powder (bottom). ...
Figure 3: Successive response and recovery cycles during exposure to increasing concentrations of nitrogen di...
Figure 4: Successive response and recovery cycles during exposure to increasing concentrations of nitrogen di...
Figure 5: Resistance change of an indium oxide sensor suddenly exposed to UV light (the UV diode is switched ...
Figure 6: Response and recovery cycles of an indium oxide sensor exposed to different concentrations of nitro...
Figure 7: Successive recovery, response (nitrogen dioxide, 500 ppb) and recovery cycles of an indium oxide se...
Figure 8: The instantaneous oxidation and reduction rates are defined as Roxi = [S(t + 1) − S(t)]/Δt and Rred...
Figure 9: Indium oxide sensor response under pulsed UV irradiation. The sensor was operated at room temperatu...
Figure 10: Indium oxide sensor response under pulsed UV irradiation. The sensor was operated at 50 °C. Every p...
Figure 11: Indium oxide sensor response under pulsed UV irradiation. The sensor was operated at 100 °C. Every ...
Figure 12: Analysis of the response of an indium oxide sensor operated at 50 °C under pulsing UV light. The up...
Figure 13: Calibration curves for the detection of nitrogen dioxide with an indium oxide sensor operated at th...
Figure 14: Sensor chamber used during the experiments, which can house up to six sensors (left). The chamber i...
Figure 1: Outline of the fabrication steps to form a nanohole array with a modified nanosphere lithography te...
Figure 2: SEM image (A) of a densely packed monolayer of polystyrene particles with a diameter of 1.02 μm. Su...
Figure 3: SEM images of the sphere masks etched by oxygen plasma at 18 W with different times (8–28 min). A d...
Figure 4: SEM image of a nanohole array with a hole diameter of 0.82 ± 0.04 µm. Spheres were etched for 8 min...
Figure 5: Microscopic image (A), exemplary Raman spectrum (B) and Raman maps (C–E) of the sensor slide consis...
Figure 6: Normalized signal change at a constant angle in response to binding of DEP to rGO-modified nanohole...
Figure 7: Exemplary signal traces at a constant angle for a nanohole array with D/P = 0.43 (A) with and witho...
Figure 1: Schematic view of gas sensor measuring system.
Figure 2: XRD patterns of TiO2-based sensors: a) T30 – TiO2 thin layer, flower-like TiO2 (NS0) and TiO2/SnO2 ...
Figure 3: Top-views (a,c–g) and side-views (b,h) of flower-like TiO2 nanostructures prepared via chemical oxi...
Figure 4: Gas sensing characteristics for the T30 sensor: dynamic changes in the electrical resistance upon e...
Figure 5: Response tres and recovery trec times of the T30 sensor calculated for NOx and CO(CH3)2 at differen...
Figure 6: Radar plots of the response, S, of TiO2-based nanostructured sensors: (a) T30, (b) NS0 and (c) NS1 ...
Figure 7: Comparison of the response of the sensors to various gases.
Figure 1: Color plot of the RAS signal during reactive ion etching (RIE) of a partially masked laser substrat...
Figure 2: Transients of the average reflected intensity in arbitrary units (a.u.) at a photon energy of 2.5 e...
Figure 3: Scanning electron microscopy (SEM) image of a facet of a lithographically masked and then reactive-...
Figure 4: SIMS intensity – sputter time profile of the CsAl-signal with logarithmic scaling. Displayed are pr...
Figure 5: Illustrations of the wafer layout and sample design (required in the example) to monitor the etch p...
Figure 6: Single transients of the average reflected intensity (top) and the RAS signal (bottom) at 2.4 eV of...
Figure 7: Scanning electron microscope (SEM) images of a film waveguide lens on a laser ridge. (a) Tilted top...
Figure 1: Sketch of the graphene/4H-SiC vertical device.
Figure 2: Current–voltage characteristics of the vertical graphene–4H-SiC device. The y-axis indicates the ab...
Figure 3: Current–voltage characteristics of the vertical device after the Pd contacts were glued with conduc...
Figure 4: The typical I–V curve, which describes the voltage and the current flowing through the graphene cha...
Figure 5: Isosurfaces of the molecular orbitals of the pristine C30H14 cluster before and after interaction w...
Figure 6: (a) Dependence of the binding energies of Cd and Hg on the number of heavy metal atoms on graphene ...
Figure 7: Dependence of the binding energy and HOMO-LUMO gap on number of Pb atoms. The top X axis represents...
Figure 8: Total and projected DOS (PDOS) for graphene flakes atoms of the heavy metals: C16H10 cluster withou...
Figure 9: Calculated current–voltage characteristics of the graphene/SiC junction before and after interactio...
Figure 10: Histogram plot of graphene/SiC device sensitivity (at fixed voltage of 1 V) towards different heavy...
Figure 11: Dependence of the sensitive parameter (ratio of work functions of graphene before and after interac...
Figure 1: (a) Layout of the dummy chip mimicking the size of the sensor chip and the contact pad positions an...
Figure 2: Schematic image of the isotropic conductive adhesive stamping process, sensor chip mounting, and un...
Figure 3: (a) Bottom side of the LTCC package showing the rear side of the sensor chip. (b) The sensor chip i...
Figure 4: The total resistance of an LTCC packaged dummy chip placed in a cell culture incubator before and a...
Figure 5: Normally proliferating BEAS2B cells on a dummy chip in LTCC package. (a–c) the cells grow on top of...
Figure 6: Average voltage change from the baseline over time from all sensors on one chip after cell media an...
Figure 1: SEM images of electrodes modified with a) PEDOT/PSS, b) PEDOT/PSS/CuPc, c) PEDOT/PSS/AuNP and d) PE...
Figure 2: Cyclic voltammograms of PEDOT/PSS, PEDOT/PSS/LuPc2, PEDOT/PSS/CoPc and PEDOT/PSS/AuNP sensors in (a...
Figure 3: Nyquist plots collected at −0.5 V using (a) PEDOT/PSS; (b) PEDOT/PSS/CuPc; (c) PEDOT/PSS/LuPc2; and...
Figure 4: Cyclic voltammograms of (a) PEDOT/PSS/EM-Tyr immersed in catechol 1.5 × 10−4 mol·L−1and (b) PEDOT/P...
Figure 5: Effect of the scan rate in PEDOT/PSS/AuNP immersed in catechol 10−3 mol·L−1. (a) CVs collected at 0...
Figure 6: CVs of (a) PEDOT/PSS/LuPc2 and (b) PEDOT/PSS/LuPc2-Tyr immersed in increasing concentrations of cat...
Figure 1: The chemical structure of DOB-719.
Figure 2: PLE maps (left) and the energy diagrams (right) for (a) dispersion of neat SWNTs and (b) as-prepare...
Figure 3: Absorption spectra in (a) the visible and (b) the NIR range for dispersions of SWNT (1), aqueous so...
Figure 4: PL spectra for the as-prepared (red curves) and aged (blue curves) mixtures of DOB-719 and SWNTs an...
Figure 5: PLE maps of aqueous solutions for (a) the as-prepared and (b) aged neat DOB-719 as well as (c) the ...
Scheme 1: Synthesis of DOB-719.
Figure 1: The optimized version of the transducer. The microheater resistive circuit width is 1200 µm (1.2 mm...
Figure 2: The optimized version of the transducer. The microheater resistive circuit width is 1200 µm (1.2 mm...
Figure 3: The masks for heater (a), electrode (b) and the fabricated transducer (c).
Figure 4: The Pt heater (green) and the Au interdigital electrode (blue) separate (a, b) and superimposed (c)...
Figure 5: Experimental setup for gas sensing measurements. Adapted from [35], copyright 2016, Elsevier Ltd. and T...
Figure 6: The sample holder/heating platform with the sensor inserted.
Figure 7: Cross-section of the sensing chamber – left to right: gas inlet, sample holder, thermocouple, gas o...
Figure 8: SEM images of the studied sensors (S1–S5). Gold interdigital electrodes appear as dark grey stripes....
Figure 9: 2D AFM image of S3 sensor.
Figure 10: Response of sensors S1–S5 (recorded in December 2015) to different concentrations of CO at their co...
Figure 11: S2 response (recorded in December 2015) to CO as a function of the working temperature.
Figure 12: Different composite sensor responses to relative humidity (62%).
Figure 13: Sensor cross-response (recorded in December 2015) to different concentrations of gases, at the corr...
Figure 14: Sensor response and recovery characteristics (recorded in June 2016) for sensor S2 at 300 °C, for d...
Figure 15: S2 response for different working temperatures.
Figure 16: S2 sensor response for different tested CO concentrations, under identical test conditions.
Figure 1: A scheme of a Pd-modified rod-like ZnO-based chemiresistive gas sensor.
Figure 2: XPS spectra of the chemical elements in pristine ZnO: Zn 2p and O 1s spectra, deconvoluted in two c...
Figure 3: SEM images of A) pristine and B) Pd-modified ZnO nanostructures, after thermal annealing at 550 °C....
Figure 4: A) Time response and B) calibration curves of the change of electrical resistance of chemiresistors...
Figure 5: Time response of A) pristine ZnO and B) Pd-modified ZnO, detected at with as-prepared sensors (t0) ...
Figure 6: Mean sensitivity of pristine and Pd@ZnO towards CH4, C3H8, and C4H10 gases at an operating temperat...
Figure 7: Mean sensitivity of pristine and Pd@ZnO NRs towards NO2 and C4H10 at an operating temperature of 30...
Figure 1: Schematics illustrating the beneficial action of n–n heterojunctions for the sensitization of the g...
Figure 2: Comparison between XRD patterns of a) SnO2 and 90 mol % SnO2/10 mol % TiO2; b) TiO2 and 90 mol % TiO...
Figure 3: Mössbauer transmission spectra of: a) SnO2; b) 90 mol % SnO2/10 mol % TiO2; c) 90 mol % TiO2/10 mol...
Figure 4: Dynamic changes in the electrical resistance, R, of: a) 90 mol % SnO2/10 mol % TiO2 (H2 concentrati...
Figure 5: Dynamic changes in the electrical resistance, R, of: a) 90 mol % SnO2/10 mol % TiO2; b) 10 mol % SnO...
Figure 6: Dynamic changes in the electrical resistance, R, of: a) 90 mol % SnO2/10 mol % TiO2; b) 10 mol % SnO...
Figure 7: Temperature dependence of the electrical resistance in air, R0, compared with that upon interaction...
Figure 8: a) Impedance spectra of 90 mol % SnO2/10 mol % TiO2 and 90 mol % TiO2/10 mol % SnO2 at 400 °C along...
Figure 9: Log–log plot of the inverse of electrical resistance vs the hydrogen partial pressure for: a) 90 mo...
Figure 1: Construction of the flow cell for reflectance measurements.
Figure 2: Working principle of the sensor element: the light reflected from the surface of the film and from ...
Figure 3: Characterization of the synthesized NPs and their thin films bound with PTSA. (a) TEM images of TiO2...
Figure 4: (a) UV–vis reflectance spectra of the film exposed to different ethanol concentrations and cleaned ...
Figure 5: Left: schematic diagram of height profile measurements before and after absorption of ethanol. Righ...
Figure 6: Optical response of the TiO2 NP-based thin film towards different VOCs (i.e., dependence of the shi...
Figure 1: Infrared spectra of xerogels in two wavenumber ranges: (a) 4000–2750 cm−1 and (b) 1600–400 cm−1.
Figure 2: X-ray diffraction patterns of the xerogels synthesized from PhTEOS/TEOS mixtures with 30% (Ph30), 4...
Figure 3: Adsorption–desorption isotherms of N2 at 77 K.
Figure 4: (a) Intensity of the reflected light by sensing elements Ph30, Ph40, and Ph50 at 298 K under vacuum...
Figure 5: Conditioning of the sensing element Ph40 in the presence of n-hexane at 323 K: (a) first and (b) se...
Figure 6: Detail of the variation of pressure and the response of the Ph40 sensing element in the presence of...
Figure 7: Time–response curves for three sensing elements in the presence of n-hexane at 298 K: (a) Ph30, (b)...
Figure 8: Time–response curves for the sensing element Ph40 in the presence of n-hexane: (a) 288 K, (b) 298 K...
Figure 9: Calibration curves for the Ph40 sensing element in the presence of n-hexane at 288, 298, 308, and 3...
Figure 10: Clausius–Clapeyron plots, ln C plotted against the reciprocal absolute temperature for the response...
Figure 11: Isosteric adsorption enthalpy. Dashed line: the condensation enthalpy of n-hexane on a flat liquid ...
Figure 1: Scheme of the SPREE gas sensing device.
Figure 2: Measured data of Ψ and Δ for a BK7 glass prism with a 45 nm Au coating and a 5 nm SnOx add-on layer....
Figure 3: Δ signal depending on different air pressure values at an AOI of 47.9°. The pressure was changed ev...
Figure 4: Changes in the Ψ and Δ angle spectrum due to changing gas atmosphere. Black / solid: synthetic air....
Figure 5: Comparison of the change in Ψ and Δ at an AOI of 44.5° after exposure for different concentrations ...
Figure 6: Gas measurement of C3H8 (black rectangle), CO (blue triangle) and H2 (red dots) with SPREE with an ...
Figure 7: Gas measurement of C3H8 (black rectangle), CO (blue triangle) and H2 (red dots) with SPREE at an AO...
Figure 1: Typical Raman spectra of the graphene sensor device recorded between electrodes (a) before and (b) ...
Figure 2: SEM images of a pristine single-layer graphene surface (a) and graphene functionalised by V2O5 (b).
Figure 3: XPS spectra of graphene following PLD treatment with V2O5 in the O 1s and V 2p region. A polychroma...
Figure 4: Electrical conduction response of pristine graphene (dashed line) and graphene functionalised with ...
Figure 5: Response of the graphene sensor to different concentrations of NH3 gas before (dashed line) and aft...
Figure 6: Photograph of a gas sensor device based on PLD-functionalised CVD graphene. The gap between the ele...
Figure 1: TEM images of electrochemically synthesized core–shell A) Au NPs and B) Pd NPs.
Figure 2: Schematic view of the two-pole chemiresistor based on a MWCNT network functionalized with metal NPs....
Figure 3: XPS core level spectrum of A) Au 4f and B) Pd 3d on functionalized MWCNTs.
Figure 4: SEM images of A) pristine MWCNTs, and metal-decorated MWCNTs with B) 0.3 at. %, C) 1.1 at. % Au NP ...
Figure 5: Mean sensitivity of pristine and A) Au- and B) Pd-modified MWCNTs-based sensors toward NO2 gas at d...
Figure 6: Time response of chemiresistors based on pristine and functionalized MWCNT films with A) Au loading...
Figure 7: Time response of chemiresistors based on pristine and functionalized MWCNTs films with A) Au loadin...
Figure 8: Variation of A) the response time (tResponse) and B) the recovery time (tRecovery) of pristine, Au-...
Figure 9: Comparison of mean sensitivity for four chemiresistors based on functionalized MWCTs with Au loadin...
Figure 1: Schematic structure and dimensions of an EVA–CB sample. Reproduced with permission from [20], copyright...
Figure 2: Expected relative change of the electrical resistance as a function of the time at different stages...
Figure 3: Expected relative electrical resistance change as a function of time in which the curve approaches ...
Figure 4: (a) Electroconductive map of CB channels of EVA–CB (7.75 phr CB) and (b) channel size distribution ...
Figure 5: Relative change of the electrical resistance of EVA–CB (7.75 phr CB) as a function of time in a) be...
Figure 6: Relative change of the electrical resistance of EVA–CB (7.75 phr CB) as a function of time in a) to...
Figure 7: a) ΔR/R0 max values of EVA–CB (7.75 phr CB) after 60 s exposure to various concentrations of benzen...
Figure 8: Relative change of the electrical resistance of EVA–CB (7.75 phr CB) as a function of time in diffe...
Figure 1: Optical micrograph of one of the CVD graphene-based chemiresistive devices. The graphene strip is h...
Figure 2: (Left): Raman spectra acquired in different points of the graphene film. (Right): Plot of I(D)/I(G)...
Figure 3: Dynamic response of devices A (left) and B (right) during the exposure to 1 ppm of NO2.
Figure 4: Dynamic response of devices A (left) and B (right) during the exposure to 250 ppm of NH3.
Figure 1: Particle size distribution of the synthesized dispersed graphene in the prepared suspension measure...
Figure 2: Pictures of the four investigated devices. D-P17 and D-P25 are the paper-based devices, while D-AO ...
Figure 3: I–V curve of a chemiresistor printed on paper (D-P17). Data are collected in the range [−5 V, 5 V].
Figure 4: a) Dynamic responses of the paper-based devices (D-P17 blue line and D-P25 black line), exposed to ...
Figure 5: Dynamic responses of the four investigated devices exposed to 1 ppm NO2. The curves have been norma...
Figure 6: a) AFM image of the paper substrate (rms roughness: 12 nm). b,c) Typical AFM images on LPE graphene...
Figure 7: a) AFM image of the Al2O3 substrate (rms roughness: 35 nm). b) AFM image of LPE graphene printed on...
Figure 1: Pyrolysis/combustion plasma system.
Figure 2: Vitrification plasma system: 1) torch, 2) feeder, 3 and 6) thermocouples, 4 and 7) windows, 5) cruc...
Figure 3: XRF analysis of feed.
Figure 4: XRF analysis of product.
Figure 5: SEM images of feed and product.
Figure 6: Photographs of a) fly ash and b) vitrified slag.
Figure 1: FE-SEM images of NiO nanowires at different magnifications (top), SnO2 nanowires (middle) and ZnO n...
Figure 2: Raman spectrum of NiO nanowires deposited on alumina substrate measured in ambient air at room temp...
Figure 3: Raman spectrum of SnO2 nanowires deposited on alumina substrate measured in ambient air at room tem...
Figure 4: Raman spectrum of ZnO nanowires deposited on alumina substrates measured in ambient air at room tem...
Figure 5: SEM picture of WO3 nanowires on alumina substrate.
Figure 6: Raman spectrum performed on WO3 nanowire deposited on alumina substrate measured in ambient air at ...
Figure 7: SEM images of Nb2O5 nanoflowers at 25k (left) and 75k (right) magnification level.
Figure 8: Raman spectrum of Nb2O5 nanoflowers deposited on alumina substrate measured in ambient air at room ...
Figure 9: Dynamic response of NiO and Nb2O5 sensing devices towards (a) (CO; 50 ppm, NiO (300 °C) and Nb2O5 (...
Figure 10: Sensor response towards 50 ppm of CO (left) and 1 ppm of NO2 (right) as a function of the temperatu...
Figure 11: Calibration curves and power-law fitting for CO (left) and NO2 (right). The relative humidity was k...
Figure 12: Principal component analysis (PCA) score plot for drinking water (blue and green dots) and a soluti...
Figure 13: Content of VOCs over seven days of analysis.
Figure 14: Growth of 1D structures by evaporation–condensation.
Figure 15: Flow chart describing the synthesis process of tungsten oxide nanowires.
Figure 16: Flow chart describing the synthesis process for niobium oxide nanostructures by hydrothermal treatm...