Figure - available from: Journal of Materials Science: Materials in Electronics
This content is subject to copyright. Terms and conditions apply.
Source publication
The light scribe (LS) technique has been applied to reduce graphene oxide (LSGO) over a flexible substrate to be used as a humidity sensor. Graphene oxide (GO) suspension was drop casted over Polyethylene terephthalate (PET) substrate and then reduced inside a conventional light scribe digital video disc (DVD). Interdigitated electrode was precisel...
Similar publications
A humidity sensor plays a crucial role in determining the efficiency of materials and the precision of apparatuses. To measure and control humidity, a non-stoichiometric Li1.1Co0.3Fe2.1O4 mesopore sensor is synthesized by a modified citrate auto combustion technique. The XRD study confirms that prepared nanoparticles are cubic spinel structures hav...
Citations
... Since the literature demonstrates that humidity affects the resistance of graphene [26,40,41], tests were performed to verify whether relative humidity (RH) would affect the response of the evaluated sensor. In these tests, the oxygen gas concentration was kept constant at ambient conditions (21% O 2 ). ...
In this work, we report the development of a new graphene oxide (GO) sensor based on a microstrip antenna for detecting and measuring O2 concentration. GO was prepared from natural graphite powder using a modified Hummers procedure and then deposited upon a phenolic substrate to act as the sensing element of the designed device. Detection tests employing the sensor to evaluate oxygen gas (O2) in higher concentrations were performed, whereas it was observed that the two operating frequencies of the device was displaced to higher values as the concentration oxygen gas increased. The effect of relative humidity (RH) in the response sensor too was observed, whereas the 9.704 GHz mode demonstrating to be the most sensitive to O2 variation after sensitivity values have been corrected, presenting limit of detection (LOD) equal to 0.38%O2. Evaluating the results, it is possible to note that the device studied could be used as sensor in medical equipment operating at elevated oxygen concentrations, such as ventilators, O2 concentrators, and other medical equipment. Moreover, evaluated sensor would be a promisor candidate for healthcare monitoring applications for the reason that this device could act as both an O2 sensor and antenna, and thus transmitting their information to other devices.
... The increment in humidity results in a rise in the quantity of hydronium ions (H 3 O + ), which can freely move between adjacent water molecules, leading to a notable reduction in the sensor's resistance [27]. This phenomenon is commonly referred to as the Grotthuss mechanism. ...
The lack of low-cost methods to synthesize large-area graphene-based materials is still an important factor that limits the practical application of graphene devices. Herein, we present a facile method for producing large-area graphene oxide-metal (GO-M) films, which are size controllable and transferable. The sensor constructed using the GO-M film exhibited humidity sensitivity while being unaffected by pressure. The relationship between the sensor's resistance and relative humidity followed an exponential trend. The GO-Mg sensor was the most sensitive among all the tested sensors. The facile synthesis of GO-M films will accelerate the widespread utilization of graphene-based materials.
... This behavior might be related to the polarizability of water molecules. As the frequency increased, the water molecules cannot follow the rapid alternation of the applied signal, causing the impedance variation to decrease [55][56][57]. Although, the highest variation value was achieved at 100 Hz, subsequent evaluations for other sensors were performed at 1 kHz due to the linearity of the measured values. The variation of impedance as a function of humidity level for all tested sensors at 1 kHz is depicted in (Fig. 6(b)). ...
... The variation of impedance as a function of humidity level for all tested sensors at 1 kHz is depicted in (Fig. 6(b)). The sensitivity (S) of all sensors was calculated using the following equation [56]: ...
... Apart from that, laser-scribed rGO also shows suitable conductivity and chemical stability, allowing it to be utilized in humidity sensing [38,39]. Fast and highly sensitive graphene-based humidity sensors produced in a single-step laser fabrication have been reported [40][41][42][43] as films with all-graphene interdigitated rGO-GO-rGO structure in a wide humidity range of 6.3% to RH 100% and response/recovery in the range of several seconds, compared among the best performing materials. Moreover, laser-structured GO sensors also exhibit good repeatability and long-term stability (>one year) [41]. ...
... For example, the frequency associated with the maximum of the semi-circle of rGO is at around 7 MHz (Figures 9a and S4), which needs frequencies at several 10 MHz to obtain the full spectra (complete semi-circle). In the case of all-graphene sensors based on laser rGO-GO-rGO structure have utilized the same equivalent circuit ((R f + Z w )/C f ), where Z w represents the water diffusion impedance, to interpret the humidity sensing mechanism [43,76]. However, this model cannot be considered as it underestimates the rGO-GO heterojunction and the contribution of rGO, which can contribute significantly, depending on the degree of reduction. ...
In this paper, the relative humidity sensor properties of graphene oxide (GO) and graphene oxide/multiwalled nanotubes (GO/MWNTs) composites have been investigated. Composite sensors were fabricated by direct laser scribing and characterized using UV-vis-NIR, Raman, Fourier transform infrared, and X-ray photoemission spectroscopies, electron scanning microscopy coupled with energy-dispersive X-ray analysis, and impedance spectroscopy (IS). These methods confirm the composite homogeneity and laser reduction of GO/MWNT with dominant GO characteristics, while ISresults analysis reveals the circuit model for rGO-GO-rGO structure and the effect of MWNT on the sensor properties. Although direct laser scribing of GO-based humidity sensor shows an outstanding response (|ΔZ|/|Z| up to 638,800%), a lack of stability and repeatability has been observed. GO/MWNT-based humidity sensors are more conductive than GO sensors and relatively less sensitive (|ΔZ|/|Z| = 163,000%). However, they are more stable in harsh humid conditions, repeatable, and reproducible even after several years of shelf-life. In addition, they have fast response/recovery times of 10.7 s and 9.3 s and an ultra-fast response time of 61 ms when abrupt humidification/dehumidification is applied by respiration. All carbon-based sensors’ overall properties confirm the advantage of introducing the GO/MWNT hybrid and laser direct writing to produce stable structures and sensors.
... The flexible humidity sensor characterization was carried out using a saturated solutions approach, allowing relative humidity levels to be consistently maintained. In this procedure, saturated salt solutions were made in cylindrical sealed Teflon jars to provide the necessary relative humidity (RH) values using a saturated solution, 51 and, furthermore, the RH of the sealed jars was measured using a commercially available humidity sensor. The RH associated with the saturated salts employed in this experiment were LiCl (11% RH), CH 3 COOK (23% RH), MgCl 2 (33% RH), K 2 CO 3 (43% RH), (MgNO 3 ) 2 (54% RH), CuCl 2 (62% RH), NaCl (75% RH), KCl (85% RH), KNO 3 (93% RH), and K 2 SO 4 (97% RH) at room temperature. ...
The resistive type of graphite/WO 3 nanocomposite-based humidity sensor is fabricated through screen printing on a flexible polyethylene terephthalate substrate. Three different nanocomposite-based humidity sensors have been fabricated and analyzed for their humidity-sensing characteristics. The structure elucidation of the nanocomposite was carried out using x-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy. By exposing the printed humidity sensor to relative humidity ranging from 11% to 97% at room temperature, its capabilities were studied. The relative resistance, sensitivity, dynamic response, and hysteresis were determined for all three devices, and they showed maximum responses towards relative humidity changes with the highest sensitivity of ≈ 60.8% and excellent hysteresis curves (maximum change of ≈ 1%). The screen-printed flexible humidity sensor exhibited less than a 5% change in the internal electrical resistance when subjected to various bending angles.
... Zhang et al. prepared RGO/MnO 2 -CNTs by microwave-assisted hydrothermal and the specific capacitance value reached 250 F g -1 at 10Ag -1 in 1.0 M of Na 2 SO 4 as an electrolyte [24]. On the other hand, CNMs-based metal oxides have been intensively studied as a promising material for improving the performance and efficiency of sensors [6], 25,26. For instance, the detection of hydrogen peroxide has received great attention due to its significance in a number of industrial sectors [6]. ...
Electrochemical alongside the electro-catalytic properties of graphene and
multi-walled carbon nanotubes have been improved via doping with manganese oxide nanostructures. Structural, morphological, and electrochemical
properties of the as-synthesized nanocomposites were identified using XRD,
FTIR, SEM, and electrochemical methods including cyclic voltammetry, and
electrochemical impedance spectroscopy. The SEM images showed flower-like
microsphere structures, while the conjugation of MnO2 with the carbon nanomaterials was confirmed by the FTIR and XRD analysis. All MnO2-based
nanocomposites provided great enhancement in their electrochemical activities
with a larger value of specific capacitance than the individual constituents of
carbon nanomaterials. Accordingly, hydrogen peroxide-directed detection was
evaluated, whereas the nanocomposites exhibited direct electron transfer, fast
and linear responses in the range from 1.0 to 210 lM. Thus, the significant
enhancements in the electrochemical features acquired by the nanocomposites
could suggest these nanomaterials for energy storage and hydrogen peroxide
sensing applications.
... More importantly, the curvature of the developed semicircle increases as the humidity increases. The sensing mechanism can be explained based on the Grotthuss chain reaction 41,61,62 . At low humidity level the adsorbed water molecules are dissociated on the surface of the sensor to form protons (H + ) and hydroxyl groups (OH − ). ...
Relative humidity (RH) is one of the most important factors that deserve intensive study because of its impact on many aspects of life. In this work humidity sensor based on carbon nitride / graphene quantum dots (g-C3N4/GQDs) nanocomposites have been developed. The structure, morphology and composition properties of the g-C3N4/GQDs were investigated and analyzed by XRD, HR-TEM, FTIR, UV–Vis, Raman, XPS and BET surface area. The average particle size of GQDs was estimated from XRD to be 5 nm and confirmed using HRTEM. The HRTEM images prove that the GQDs are attached to the external surface of the g-C3N4. The measured BET surface area was found to be 216 m2/g, 313 m2/g, and 545 m2/g for GQDs, g-C3N4, and g-C3N4/GQDs respectively. The d-spacing and crystallite size were estimated from XRD and HRTEM and found in a good matching. The humidity sensing behavior of g-C3N4/GQDs was measured in a wide span of humidity from 7% up to 97% RH under different testing frequencies. The obtained results demonstrate good reversibility and fast response/recovery time. The implemented sensor exhibits a great application prospect in humidity alarm devices, automatic diaper alarms, and breath analysis, which have advantages such as strong anti-interference capability, low cost, and easy to use.
... XRD was performed to investigate the impact of nanoparticles on the morphological structure of PUF. Figure 1 illustrates the XRD patterns of native PUF and shows the features of the fabricated PUF/rGO, as well as PUF/rGO/ZnO samples with 2θ ranges from 5 • to 90 • . It was found that a relatively wide diffraction peak appeared at 2θ~20.80 • , which was assigned to the amorphous structure of the PUF [35][36][37]. After GO nanosheets were added to the PUF matrix, a relatively sharp diffraction peak appeared at 2θ~9.7 o , corresponding to the (001) basal plane of GO, when compared to 2θ = 11.40 • for native GO nanosheets [38]. ...
... XRD was performed to investigate the impact of nanoparticles on the morphological structure of PUF. Figure 1 illustrates the XRD patterns of native PUF and shows the features of the fabricated PUF/rGO, as well as PUF/rGO/ZnO samples with 2θ ranges from 5° to 90°. It was found that a relatively wide diffraction peak appeared at 2θ ~ 20.80°, which was assigned to the amorphous structure of the PUF [35][36][37]. After GO nanosheets were added to the PUF matrix, a relatively sharp diffraction peak appeared at 2θ ~ 9.7 o , corresponding to the (001) basal plane of GO, when compared to 2θ = 11.40° for native GO nanosheets [38]. ...
... Moreover, impurities were not detected in the diffraction patterns, supporting the purity of the synthesized structure. The average crystallite size of ZnO NPs was estimated from the well-known Scherrer equation [35] ...
The demand for reactive dyes in industries has increased rapidly in recent years, and producing a large quantity of dye-containing effluent waste contaminates soils and water streams. Current efforts to remove these harmful dyes have focused on utilizing functionalized nanomaterials. A 3D polyurethane foam loaded with reduced graphene oxide (rGO) and ZnO nanocomposite (PUF/rGO/ZnO) has been proposed as an efficient structural design for dye degradation under the influence of visible light. The proposed structure was synthesized using a hydrothermal route followed by microwave irradiation. The resultant 3D PUF/rGO/ZnO was examined and characterized by various techniques such as XRD, FTIR, SEM, EDAX, BET, and UV–visible spectroscopy. SEM data illustrated that a good dispersion and embedment of the rGO/ZnO NPs within the PUF matrix occurred. The adsorption capacity for neat PUF showed that around 20% of the Methylene blue (MB) dye was only adsorbed on its surface. However, it was found that an exceptional adsorption capacity for MB degradation was observed when the rGO/ZnO NPs inserted into the PUF, which initially deteriorated to ~ 70 % of its initial concentration. Notably, the MB dye was completely degraded within 3 h.
In this paper, we present a humidity sensing material based on nanostructured Zn(1.6 − x)Na0.4CuxTiO4 spinel to enhance optical and sensitivity performance. Nano-porous of Zn (1.6 − x) Na0.4CuxTiO4 spinel were synthesized using sol gel reactions and calcined at 700 °C. The nanostructures of Zn(1.6 − x)Na0.4CuxTiO4 spinel underwent thorough characterization through multiple techniques. X-ray diffractometry (XRD) coupled with Rietveld refinement using FullProf software, transmission electron microscopy (TEM), Raman Spectroscopy, and optical analysis were employed to assess various aspects of the nanostructures. These techniques were utilized to determine the phase composition, particle size distribution, chemical bonding, and the tunable band gap of the nanostructures. The X-ray diffraction (XRD) analysis of Zn(1.6 − x)Na0.4CuxTiO4 samples revealed well-defined and prominent peaks, indicating a highly crystalline cubic spinel structure. The lattice parameter was decreased from 8.4401 to 8.4212 Å with increasing Cu content from 0 to 1.2 mol%. UV–visible diffuse reflectance spectra were employed to investigate the optical characteristics of copper-doped Zn1.6Na0.4TiO4. The applicability of Cu@NaZT spinel nanostructures in humidity sensors was evaluated at ambient conditions. The fabricated sensor was investigated in a wide span of humidity (11–97%). The examined sensor demonstrates a low hysteresis, excellent repeatability, fast response and recovery. The response and recovery times were estimated to be 20 s and 6 s respectively. The highest sensitivity was achieved at 200 Hz. The proposed sensor can be coupled easily with electronic devices as the humidity–impedance relationship is linear.
This letter presents a human nose breath sensor based on Partially Reduced Graphene Oxide (PrGO) operating at room temperature. The sensing layer is developed by drop casting Graphene Oxide (GO) on a glass substrate with silver electrodes and was partially reduced thermally at 150°C. The results with GO film have also been compared. The developed sensor was successful in detecting various breath patterns by observing the frequency and amplitude of the sensor's current change to exposure to nose breath. The sensor was capable of differentiating between slow, normal and fast breathing based on the response and recovery time. This sensor can be very useful for characterization of diseases such as Asthma, COPD, sleep apnea and cardiac arrest where the person's respiration rate is measured.
