Sensitive Chemiresistive Sensors Research Articles

Gas sensing behavior of metal-catecholates based MOFs

We report on the usability aspect of triphenylene ligand-based metal–organic frameworks (MOF) as the potential gas sensing element in chemiresistive devices. Among various possibilities, we explored mono-metallic (Nickel-based) and bi-metallic (Nickel and copper-based) in room temperature gas sensing. Our investigations suggest that the chemiresistive device based on nickel catecholate MOFs were highly sensitive to ethyl alcohol gas in the concentration range of 5–100 ppm with decent sensing parameters such as response time, recovery time, repeatability, stability, etc. We also investigated bimetallic (Nickel and copper) catecholate based MOFs in gas sensing with different metallic content ratios (Cu: Ni:: 60:40 and 40:60). We found that the 1D Cu0.6Ni0.4-CAT nanostructures-based gas sensor to be selective towards H2 gas (0.2–7 ppm) at room temperature. We further explored the gas sensing abilities of Cu0.4Ni0.6-CAT based devices, and we found them to be selective towards NO2 gas. However, it was not possible to obtain the current versus concentration curve due to the gas molecules’ aggressive chemisorption. However, the device could perform well (with a hysteresis error of ∼10%) for detecting NO gas (which has the 2nd best absolute response after NO2). These results indicate that the ratio of metal ions in the MOF directly influences the sensing capabilities. Hence, rational synthetic variations in the metal content in MOF can lead to the design and develop highly selective and sensitive chemiresistive sensors.

Selective and sensitive chemiresistive sensors based on polyaniline/graphene oxide nanocomposite: A cost-effective approach

In this work, the influence of Graphene oxide (GO) on the sensing performance of Polyaniline (PANI) toward NH 3 and CO gases at room temperature (RT) was comprehensively studied. The PANI/GO nanocomposite was synthesized by the “ in-situ chemical oxidation polymerization” route in the presence of GO. The optical, spectroscopic and structural properties of as-prepared materials were studied through UV–vis, FTIR, RAMAN spectroscopies and XRD. Additionally, the topological investigations of materials were carried out by Atomic Force Microscopy (AFM). The sensors were fabricated via drop-casting of the pure PANI and PANI/GO nanocomposite on a low-cost pattern of Cu interdigitated electrodes (IDE). The sensors based on the PANI/GO nanocomposite exhibited a better-sensing performance for NH 3 than those of bare PANI. The present finding indicates that the PANI/GO-based sensor exhibits high response (9.6%–70 ppm), fast recovery time (23 s), low detection limit (30 ppm) and linear dynamic range (30–230 ppm) with excellent repeatability, reproducibility, long-term stability and exceptional selectivity for NH 3 sensing. Thus, the PANI/GO-based sensor has a high potential for high-performance sensing applications.

Gold Nanoparticles Monolayer Doping PEDOT : PSS Janus Film for Hydrogen Sulfide Sensor

AbstractAuNPs monolayer doping Poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT : PSS) film on interdigitated electrode had been fabricated into AuNPs/PEDOT : PSS Janus film sensor to detect hydrogen sulfide (H2S). The results show that the Janus film sensors have a wide measurement range of H2S concentration. The sensitivity of PEDOT : PSS/AuNPs sensor grows up with the thickness of Janus film increases. The resistance response of AuNPs Janus film was affected little by the rough surface states of PEDOT : PSS film. In addition, the PEDOT : PSS/AuNPs film sensor had been used again to detect H2S. This work presents a platform to inspire a novel high sensitive chemiresistive sensor via nanoparticles monolayer.

Confinement of Ultrasmall Bimetallic Nanoparticles in Conductive Metal–Organic Frameworks via Site‐Specific Nucleation (Adv. Mater. 38/2021)

NO2 Sensors In article number 2101216, Il-Doo Kim and co-workers demonstrate a conductive metal–organic framework (cMOF) with enhanced activity owing to encapsulation of ultrasmall bimetallic nanoparticles (BNPs) within the cMOF matrix. The combination of the high surface area of the cMOF and the bimetallic synergies of the PtRu BNPs enables application as a highly sensitive chemiresistive sensor toward NO2 detection.

Noninvasive Detection of Ammonia in the Breath of Hemodialysis Patients Using a Highly Sensitive Ammonia Sensor Based on a Polypyrrole/Sulfonated Graphene Nanocomposite.

In this work, we fabricated fast-responsive and highly sensitive chemiresistive sensors based on nanocomposites of polypyrrole and graphitic materials such as graphene oxide (GO), reduced graphene oxide (RGO), and sulfonated graphene (SRGO) by an in situ chemical oxidative polymerization method. The synthesized nanocomposites were characterized using field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The effects of the operating temperature of different nanocomposites were investigated at four temperatures (28, 40, 50, and 60 °C), and the results were compared with that of the polypyrrole-based sensor. The experimental results for sensors indicate that the proposed PPy/SRGO sensor could be an appropriate choice for NH3 detection at 28 °C in the range of 0.50 parts per billion (ppb) to 12 parts per million (ppm). The PPy/SRGO nanocomposite gas sensor exhibited fast responsivity, good repeatability, and high chemical selectivity to low-concentration ammonia against humidity, methanol, ethanol, acetone, formaldehyde, dibutylamine, dimethylamine, methylamine, carbon monoxide, and nitrogen oxide at 28 °C. We utilized the PPy/SRGO sensor for studying the variation of the ammonia concentration in hemodialysis (HD) patients' breath before and after dialysis and correlated it with the blood urea nitrogen (BUN) levels. The results of the PPy/SRGO sensor indicated that the breath ammonia concentration significantly decreased after dialysis in agreement with BUN. The results demonstrate the potential application of the PPy/SRGO sensor for noninvasive detection of ammonia in breath and make this type of sensor a promising tool for the diagnosis of renal and liver diseases.

Solution processed, vertically aligned, AZO nanocolumn array for chemiresistive sensor application with UV-enhanced sensitivity

In this work, a wide and highly sensitive chemiresistive sensor has been developed based on the AZO nanocolumn array film. This is meant for the room detection of H2O2 under UV illumination. A cost-effective one step multi-layers growth process was adopted for the synthesis of the AZO nanocolumn array. The experimental studies were done by scanning electron microscopy (SEM), transmission and electron microscopy (TEM).Then X-ray diffraction confirmed that the AZO column array was closely packed, connected, vertically aligned, and polycrystalline, with a high surface area. This structure ensures better electrical conduction over random and separated nanostructures. The hall-effect measurement indicates that the AZO film was n-type, with high conductivity (3.60 × 103 Ωcm), high carrier density (11.3 × 1020cm−3) and with acceptable mobility (0.95 cm2/Vs). The x-ray photoemission spectroscopy suggests that the AZO film consists of a large amount of adsorbed oxygen-related species at the sheath layer of the thin-film, which is vital for sensors. By the UV light activation, sensors based on the AZO nanocolumn array exhibited enhanced H2O2 detection properties at room temperature. At a concentration from 15 μM to 30 mM, H2O2 sensitivity evaluated by relative response was remarkably increased from 15% to 36%. The operation under ambient conditions and wide range sensing shows that this chemiresistive AZO sensor is adequate for biomedical and environmental applications.

A high-performance low-temperature LPG detection by MgFe2O4/BiVO4 chemiresistive sensor

Liquid petroleum gas (LPG) is an extensively used cooking fuel and autogas that is toxic, explosive in nature, and has a considerable effect on humans and environment. The present study reports the development of a highly sensitive chemiresistive sensor towards LPG operating at low temperatures. A two-step process of solution combustion and hydrothermal method has been adopted for the synthesis of MgFe2O4/BiVO4 nanocomposite. This work reports the synthesis of the novel nanocomposite; catalytic BiVO4 incorporated in the porous MgFe2O4 and its application for LPG sensing. X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, and energy dispersive X-ray spectroscopy were used to analyse the structural, morphological, and compositional studies of prepared nanomaterials. LPG detection was carried out from 50 to 500 ppm, and the sensor with 8:1 at% showed a peak response of 58%, with short response time 37 s and 42 s of recovery towards 500 ppm of LPG at low operating temperature of 50 °C. Besides, the fabricated low-cost sensor showed excellent selectivity and long-term stability towards LPG. Highly efficient LPG sensing device fabrication can be facilitated by this sensor.

Effect of carbon derivatives in sulfonated poly(etherimide)–liquid crystal polymer composite for methanol vapor sensing

A class of highly sensitive chemiresistive sensors is developed for methanol (MeOH) vapor detection in ambient atmosphere by introducing conductive nanofillers like carbon black, multi-wall carbon nanotubes, and reduced graphene oxide into sulfonated poly(etherimide) (PEI)/liquid crystal polymer (LCP) composite (sPEI-LCP). Polar composites are prepared by a sulfonation process for instantaneous enhancement in adsorption capability of the sensing films to the target analyte (MeOH). Sensing properties exhibit that polymer composite-based fabricated sensors are efficient for the detection of different concentration of methanol vapor from 300–1200 parts-per-million (ppm) at room temperature. The incorporation of nanofiller induces the dramatic change in sensing behavior of base composite film (sPEI-LCP). Thus, less mass fraction of nanofillers (i.e. 2 wt%) influences the nonlinear sensing behavior for the entire range of methanol vapor. The simple method and low fabrication cost of the prepared sensor are compelling reasons that methanol vapor sensor is suitable for environmental monitoring.

Impact of Doping on GO: Fast Response-Recovery Humidity Sensor.

Nowadays, humidity sensors have become essential in numerous applications. However, there are several problems while using them for humidity detection, such as low sensitivity, delayed response and recovery times, less stability, and narrow humidity detection ranges. Here, we demonstrate for the first time a highly sensitive chemiresistive sensor for low-level humidity detection in ambient atmosphere by introducing graphene oxide (GO) and doped GO (Li-doped GO and B-doped GO) as a thin film in a facile manner. The sensitivity, repeatability, and stability studies show that thin film-based fabricated humidity sensors are unprecedently efficient in the detection of different percentages of humidity from 11 to 97% at room temperature. The incorporation of doping into GO induces a dramatic change in the sensing behavior of the base film (undoped GO). This allows the sensor to be used in a variety of applications such as humidity sensing, which we validate through our experiment with a “cheap and readily available” recognition system.

Au Nanocomposite Based Chemiresistive Ammonia Sensor for Health Monitoring

We have developed a fast and highly sensitive chemiresistive sensor based on the nanocomposite of polysaccharide (guar gum) and gold nanoparticles for the room temperature detection of ammonia in the range of 0.1 parts-per-quadrillion (ppq) to 75 000 parts-per-million (ppm). Sensor response, selectivity, and stability studies reveal excellent sensing of the nanocomposite. The room temperature operation under ambient conditions and the wide range sensing indicates that the composites can be explored for environmental as well as biomedical applications. We have for the first time quantified the ammonia level released from the urine and blood serum of human beings using the resisitive sensor. The urine ammonia level was found to be ∼24 000 ppm and is higher for patients with renal problems. This demonstrated the utility of the sensor for health monitoring.

Structural changes in stimuli-responsive nanoparticle/dendrimer composite films upon vapor sorption

Au-nanoparticle/dendrimer composite films are stimuli-responsive materials with a potential application as highly sensitive chemiresistive sensors, since their conductance strongly changes upon sorption of chemical species from vapor phase. Here we report on the neutron reflectometry studies on such films exposed to water, methanol, and toluene vapors as external stimuli. Poly (amidoamine) (PAMAM) dendrimer third generation and poly (propylene imine) (PPI) dendrimer fourth generation were used to build up the films. The interaction between the film and the vapor is mainly governed by the chemical nature of the dendrimer component. Both AuPAMAM and AuPPI films have well expressed affinity to water. The more hydrophilic PAMAM adsorbs about 3 times more water than the more hydrophobic PPI. In contrast, the diffusion of toluene is limited to a thin region near the film/gas phase interface where a thin wetting layer of toluene is registered. Methanol as a solvent with transitional hydrophilicity shows intermediate behavior when interacting with the films. Since this work is largely based on neutron reflectometry we point out that this technique is outstanding in resolving fine details of film response to vapors which is important to understand the changes that occur in the vapors sensing process.