Ammonia Sensor Research Articles

Ammonia Sensing Behavior of Green- Synthesized ZnO Nanoparticles Using Optical Density as Sensing Parameter

Ammonia Sensing Behavior of Green- Synthesized ZnO Nanoparticles Using Optical Density as Sensing Parameter

Room temperature ZnO nanorods based TFT ammonia sensor: an experimental and simulation study

Room temperature ZnO nanorods based TFT ammonia sensor: an experimental and simulation study

Poly3‐hexylthiophene titanium dioxide (P3HT‐TiO2) composite sensor for high response detection of ammonia at room temperature

Gas sensors for ammonia (NH3) play a crucial role in the maintenance of air quality, preservation of the atmosphere, and evaluation of human health. However, the endeavor to attain a high level of sensitivity in detecting NH3 under ambient conditions remains a challenging task. In this work, poly(3‐hexylthiophene)s and titanium dioxide (P3HT‐TiO2) heterostructure NH3 gas‐sensitive material was prepared, and by drop‐casting the material onto a substrate with Au interdigital electrodes, a sensor for high‐response detection of NH3 at room temperature was constructed. The designed gas sensor exhibited a high response signal of 114.61% toward 15 ppm NH3 at room temperature (25°C) with good reproducibility, strong long‐term stability, and excellent selectivity. Moreover, by analyzing the response law of the sensor under different humidity conditions, it has been noted that both excessively high and excessively low levels of humidity adversely affect the sensor’s response. The remarkable increase in NH3 sensing properties is attributed to the synergistic enhancement effect of P‐N heterojunction formed between P3HT and TiO2. This NH3 gas sensor exhibits tremendous potential for use due to its straightforward structure and outstanding ammonia sensing performance.

Highly Flexible, Selective and Sensitive Ammonia Sensor Based on MXene/Cellulose Nanofibers

Highly Flexible, Selective and Sensitive Ammonia Sensor Based on MXene/Cellulose Nanofibers

Nitrogen-doped carbon nano-onions/polypyrrole nanocomposite based low-cost flexible sensor for room temperature ammonia detection

One of the frontier research areas in the field of gas sensing is high-performance room temperature-based novel sensing materials, and new family of low-cost and eco-friendly carbon nanomaterials with a unique structure has attracted significant attention. In this work, we propose a novel low-cost flexible room temperature ammonia gas sensor based on nitrogen-doped carbon nano-onions/polypyrrole (NCNO-PPy) composite material mounted low-cost membrane substrate was synthesized by combining hydrothermal and in-situ chemical polymerization methods. The proposed flexible sensor revealed high sensing performance when employed as the sensing material for ammonia detection at room temperature. The NCNO-PPy ammonia sensor exhibited 17.32% response for 100 ppm ammonia concentration with a low response time of 26 s. The NCNO-PPy based flexible sensor displays high selectivity, good repeatability, and long-term durability with 1 ppm as the lower detection limit. The proposed flexible sensor also demonstrated remarkable mechanical robustness under extreme bending conditions, i.e., up to 90° bending angle and 500 bending cycles. This enhanced sensing performance can be related to the potential bonding and synergistic interaction between nitrogen-doped CNOs and PPy, the formation of defects from nitrogen doping, and the presence of high reactive sites on the surface of NCNO-PPy composites. Additionally, the computational study was performed on optimized NCNO-PPy nanocomposite for both with and without NH3 interaction. A deeper understanding of the sensing phenomena was proposed by the computation of several electronic characteristics, such as band gap, electron affinity, and ionization potential, for the optimized composite.

TiO2 decorated MXene nanosheets for high-performance ammonia gas sensing at room-temperature

A room-temperature sensor with superior performance to detect traces of toxic gas molecules is highly desirable. MXenes, due to their unique planar structure, higher electrical conductivity and abundant functional groups on the surface, have emerged as leading low dimensional gas sensing materials. But, the gas sensors based on Ti3C2Tx MXene possess higher detection limit and poor long-term stability, thereby limiting their applications. However, TiO2 modified Ti3C2Tx as a gas sensing platform has displayed improved ammonia sensing performance. Here, we report a facile method to prepare Ti3C2Tx/TiO2 composite via calcination of Ti3C2Tx. The experimental results indicate that the oxidation temperature plays a key role in the morphology evolution and gas-sensing performance of Ti3C2/TiO2 composites. Compared to the as obtained Ti3C2Tx, the Ti3C2Tx/TiO2 composite obtained at 200 °C displays improved response to NH3 gas due to the formation of a heterointerface between Ti3C2Tx and TiO2. Room-temperature, selective ammonia detection down to 5 ppb has been obtained. Moreover, the device displayed a stable sensing response to 10 ppb of ammonia over the RH range of 26%–90%. It also displayed higher selectivity to NH3 over other analytes including dimethyl formamide, ethanol, isopropyl alcohol, methanol, acetone, chloroform, xylene and N-methyl pyrolidone. The results suggest that by appropriate engineering of the Ti3C2Tx/TiO2 composites, ammonia sensor with improved sensing performance can be designed.

Highly sensitive prismatic h-MoO3 sheets for temperature-dependent chemiresistive ammonia sensor

Highly sensitive prismatic h-MoO3 sheets for temperature-dependent chemiresistive ammonia sensor

Gamma Irradiated Cu-doped TiO2 Nanoparticles for Selective Ammonia Sensing

Gamma Irradiated Cu-doped TiO2 Nanoparticles for Selective Ammonia Sensing

Confinement Enrichment Effect in HoMS-BaTiO3 Microwave Gas Sensors for the Detection of 10 ppb-0.55 v/v% Ammonia at Room Temperature.

The construction of ammonia gas sensors with wide detection ranges is important for exhalation diagnosis and environmental pollution monitoring. To achieve a wide detection range, sensitive materials must possess excellent spatial confinement and large active surfaces to enhance gas adsorption. In this study, an ammonia microwave gas sensor with a wide detection range of 10 ppb-0.55 v/v% at room temperature was fabricated by incorporating hollow multishelled-structured BaTiO3 (HoMS-BaTiO3). The effect of the number of shells and the quantity of the sensitive material on the gas-sensing performance was investigated, and two-layered HoMS-BaTiO3 demonstrated the best response at high concentrations (0.15-0.55 v/v%). Conversely, single-layered HoMS-BaTiO3 displayed outstanding performance at low concentrations (10 ppb-0.15 v/v%). The lower the quantity of the sensitive material, the higher the response. This study offers a method for preparing room-temperature ammonia sensors with a wide detection range and reveals the link between the structure and quantity of sensitive materials and gas-sensing performance.

Development of green and sustainable ammonia sensor from xanthohumol extract-immobilized polylactic acid nanofibers

Ammonia is a significant industrial gaseous agent that is colorless. However, long exposure to ammonia gas can cause organ damages or even death. This study describes the preparation of a solid-state vapochromic sensor for gaseous and aqueous ammonia using eco-friendly smart colorimetric polylactic acid nanofibers. Xanthohumol (XMOL) is a natural spectroscopic probe that can be found in the common hop (Humulus lupulus L.) plant. Nanoparticles of mordant/xanthohumol (M/XMOL) coordinated complex were synthesized by immobilizing the xanthohumol direct dyestuff into polylactic acid nanofibers in the presence of a mordant (potassium aluminum sulfate). Xanthohumol can be described as an appropriate sensor for gaseous and aqueous ammonia due to its tiny molecular size and high water-solubility. Both of CIE Lab color parameters and absorbance spectra were used to inspect the color shift of the xanthohumol-finished polylactic acid nanofibers from yellow to colorless upon exposure to ammonia. This could be attributed to the intramolecular charge transfer caused by molecular switching of xanthohumol. In a fraction of second, the polylactic acid nanofibrous fabric showed a colorimetric change with a detection limit of 10–450 mg/L. The absorption spectra of the xanthohumol probe exhibited hypsochromic shift with a wavelength change from 465 nm to 315 nm (isosbestic point of 370 nm) in response to an aqueous solution of ammonia. Transmission electron microscopic (TEM) images showed that M/XMOL particles were 13–27 nm in diameter, whereas scanning electron microscopic (TEM) images demonstrated that the polylactic acid nanofibers were 150–450 nm in diameter. We observed no significant differences in air-permeability and bending-length of the nanofibrous fabric after immobilization of M/XMOL into polylactic acid nanofibers. In addition, the colorfastness properties of the treated polylactic acid nanofibers were investigated.

A flexible ammonia sensor based on MXene membrane with high sensitivity

AbstractAmmonia (NH3) of high concentration will pose a threat to ecological environment or human health, and exhaled NH3 is significant in disease monitoring and diagnosis. Thus, developing a highly sensitive gas sensor is significant to monitor NH3 concentration in complex environments. However, traditional NH3 sensors either need high working temperature, or face the challenge of poor conductivity/ sensitivity. In this work, NH3 sensors based on self‐assembled MXene membrane have been fabricated. As‐prepared sensors show a high sensitivity of 2.10 ppm−1 towards extremely low concentrations of NH3 (ppb level) at room temperature, attributed to large surface area and high conductivity. In addition, the sensors also display low detection limit (50 ppb), fast response time (41 s), good recoverability, long‐term stability (15 days) and excellent flexibility (1000 bending cycles) towards NH3. The results provide insights into the development of highly sensitive NH3 sensors for industrial or biomedical applications.

Room-Temperature Phosphorescence Materials Featuring Triplet Hybrid Local Charge Transfer Emission.

Room-temperature phosphorescence materials have found important applications in dissolved oxygen sensing, temperature monitoring, anticounterfeiting, etc., because of their prolonged phosphorescence lifetime. However, the known systems mainly utilize the triplet local excited state emission, which is generally less sensitive to microenvironment perturbation. In this work, we designed a series of 4-phenyl-1,8-naphthalimide (NMI) derivatives containing different numbers of carbazole (Cz) units (denoted as NMI-Cz, NMI-2Cz, and NMI-3Cz). Steady state and time-resolved spectroscopy studies determined that the compounds undergo intramolecular through-space charge transfer in solution, yielding a triplet hybrid local charge transfer state. Room-temperature phosphorescence emission was observed in compound-doped poly(methyl methacrylate) thin films upon ammonia treatment. Interestingly, emission from different films exhibited different persistence times. We believe a film-based, time-resolved luminescent ammonia sensor could be developed by making a device of the emissive films as fabricated.

Highly sensitive detection of ammonia based on light-induced thermoelastic spectroscopy with hollow waveguide

In this paper, an ammonia (NH3) sensor based on light-induced thermoelastic spectroscopy (LITES) with hollow waveguide (HWG) is proposed for the first time. HWG has many advantages, such as small size, simple structure, high system stability and fast filling speed. The sensor used HWG with a length of 22 cm and an inner diameter of 4 mm as the light transmission medium and gas chamber. The interior of the HWG is covered with silver (Ag) and silver iodide (AgI). The reflectivity is increased and the transmission losses is reduced in the infrared region of the HWG. A diode laser with an output wavelength of 1.53 μm was employed, which can cover the two NH3 absorption lines of 6534.6 cm−1 and 6533.4 cm−1. The amplitude of the second harmonic signal (2f) showed a good linear response to the gas concentration. The experiments demonstrated that the NH3 sensor's minimum detection limit (MDL) under this system was 9.896 parts per million (ppm).

Room-temperature NH3 sensor based on CoFe2O4/PANI composite with porous structure

Development of chemo-resistive room-temperature ammonia (NH3) sensor with high performance remains a great challenge to this day. In this paper, we demonstrate a room-temperature NH3 sensor based on organic-inorganic cobalt ferrite (CoFe2O4)/polyaniline (PANI) composite. The CoFe2O4 porous nanosheets were firstly prepared by using a direct precipitation method, and then the PANI were anchored onto the surfaces of the CoFe2O4 porous nanosheets through an in-situ polymerization process to form the CoFe2O4/PANI composite. The crystal structure, morphology, and surface chemistry of the CoFe2O4/PANI composite were characterized by combined techniques of X-ray diffraction, electron microscopy, and spectroscopy. Due to the porous feature of the composite and the formation of p-p heterojunctions between the CoFe2O4 and PANI, the CoFe2O4/PANI gas sensor exhibited excellent NH3-sensing performance with high response (13 to 100 ppm NH3), good selectivity, wide detection range (10–500 ppm), and rapid response/recovery rate (18/31 s to 100 ppm NH3) at room temperature. Additionally, the CoFe2O4/PANI gas sensor owned outstanding repeatability and long-term stability. This study offered a promising candidate of CoFe2O4/PANI composite for constructing room-temperature NH3 sensor.

Enhanced electrocatalytic oxidation activity of platinum-poly(methylene blue) as a sensitive sensor for ammonia–nitrogen detection

To achieve highly effective electrochemical determination of ammonia–nitrogen in the aqueous environment, in this work, based on the great electrocatalytic activities of platinum-poly(methylene blue) (Pt-PMB) composites for ammonia oxidation reaction, one new sensing electrode was constructed based on Pt-PMB for ammonia–nitrogen detection. PMB film was loaded on the surface of Ni foam (NF), and then, Pt film was covered on the PMB film, achieving a self-supported Pt-PMB-NF electrode. Under optimum conditions, prepared Pt-PMB-NF was analyzed via scanning electron microscopy (SEM) and element map and X-ray photoelectron spectroscopy (XPS), and the sensing performances including sensitivity, the limit of detection, selectivity and stability were measured via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques and exhibited great results. In addition, the recovery of real samples indicated that this Pt-PMB-NF electrode showed great potential for practical application.

Design of ammonia sensor based on ZnO for analyzing hazards at critical infrastructure

A gas sensor based on ZnO has been designed, which demonstrates sensitivity to NH3 under standard conditions (temperature, 25 °С; pressure, 101.3 kPa). The experimental sample was manufactured by magnetron sputtering at direct current. A VUP-5M vacuum unit with an original material-saving magnetron was used to produce ZnO films. To analyze the efficiency of the gas sensor to ammonia (NH3) under standard conditions, its operating characteristics were studied. The concentration of NH3 for investigating operating characteristics was chosen at the level of 25 ppm. To determine the resistivity of the contacts of the instrument structure, the current-voltage characteristics of the gas sensor were examined in the voltage range between −100 and +100 V. Based on the results of investigating the current-voltage characteristics, which have a linear character, the resistivity of the contacts was confirmed. To study the sensitivity of the gas sensor to the target gas, the change in resistance of the sensitive layer of the gas sensor under the influence of NH3 with a concentration of 25 ppm under standard conditions was explored. The study results demonstrated the high sensitivity of the gas sensor to the target gas – at the level of 229 relative units. The investigation of the response and recovery time of the gas sensor showed that the ZnO-based gas sensor has a response and recovery time of 20 and 26 s, respectively. The selectivity of the ZnO-based gas sensor was studied. The selectivity study was carried out by determining the sensitivity of the gas sensor in the presence of vapors of various gases, namely methanol, ethanol, acetone. The study results showed that the reaction to ammonia is selective compared to the reaction to other gases. The results of examining the working characteristics of the ammonia gas sensor demonstrate the high efficiency of its application under standard conditions and a low concentration of the target gas

Modulating the majority charge carrier type and performance of organic heterojunction ammonia sensors by increasing peripheral fluorination of the silicon phthalocyanine sublayer

Silicon phthalocyanines (R2-SiPcs) are an emerging class of high-performance organic semiconductors which have recently found application in highly sensitive and selective bilayer organic heterojunction devices for ammonia (NH3) sensing. We report bilayer heterojunction devices based on axially-substituted bis(pentafluorophenoxy)silicon phthalocyanines of increasing peripheral fluorination ((F5PhO)2-FXSiPc) as a bottom layer and lutetium bis-phthalocyanine (LuPc2) and demonstrate how increased peripheral fluorination changes device operation from p-type to n-type in response to NH3. Sensors fabricated with (F5PhO)2-F16SiPc exhibits the smallest apparent energy barrier for interfacial charge transport by impedance spectroscopy due to better alignment of the semiconductor molecular orbitals with the semi-occupied molecular orbital of LuPc2. Bilayer heterojunction devices all demonstrated a limit of detection (LOD) below 1 ppm with (F5PhO)2-SiPc/LuPc2 yielding an LOD of 307 ppb and a sensitivity of −0.72%·ppm−1. Postdeposition thermal annealing of the (F5PhO)2-SiPc/LuPc2 device is shown to further enhance sensor performance with a 1.5-fold increase in sensitivity to −1.15%·ppm−1 and a LOD of 198 ppb.

AI‐Assisted Multimodal Breath Sensing System with Semiconductive Polymers for Accurate Monitoring of Ammonia Biomarkers

AbstractBreath ammonia is an essential biomarker for patients with many chronic illnesses, such as chronic kidney disease (CKD), chronic liver disease (CLD), urea cycle disorders (UCD), and hepatic encephalopathy. However, existing breath ammonia sensors fail to compensate for the impact of breath humidity and complex breathing motions associated with a human breath sample. Here, a multimodal breath sensing system is presented that integrates an ammonia sensor based on a thermally cleaved conjugated polymer, a humidity sensor based on reduced graphene oxide (rGO), and a breath dynamics sensor based on a 3D folded strain‐responsive mesostructure. The miniaturized construction and module‐based configuration offer flexible integration with a broad range of masks. Experimental results present the capabilities of the system in continuously detecting diagnostic ranges of breath ammonia under real, humid breath conditions with sufficient sensing accuracy and selectivity over 3 weeks. A machine‐learning algorithm based on K‐means clustering decodes multimodal signals collected from the breath sensor to differentiate between healthy and diseased breath concentrations of ammonia. The on‐body test highlights the operational simplicity and practicality of the system for noninvasively tracing ammonia biomarkers.

Room-temperature operated fast reversible ammonia sensor based on hybrid optical fiber structure with temperature compensated function

An optical fiber ammonia (NH3) sensor based on multi-mode interference (MF) and anti-resonance (AR) principle is proposed, which can detect the NH3 and increase the function of temperature measurement to avoid the influence of ambient temperature. The sensor is made of single-mode fiber (SMF) - hollow core fiber (HCF) - SMF - coreless fiber (NCF) -SMF welding, wherein NCF deposited graphene oxide gas response coating by dip-coating method. HCF and NCF can excite AR valley and MF valley simultaneously in the same spectrum. Experimental results show that for NH3 gas sensing, MF valley exhibits a NH3 sensitivity of 3.28 pm/ppm with a response time of 60 s and a recovery time of 30 s, while AR valley is not sensitive. For temperature sensing, MF valley and AR valley are sensitive to temperatures of − 12.63 pm/℃ and 15.57 pm/℃, respectively. The simultaneous detection of NH3 and temperature can be realized through spectral demodulation. The gas sensor offers several advantages, including straightforward preparation, cost-effectiveness, and low operating temperature. Most importantly, it solves the problem of temperature interference that is often ignored in fiber optic gas sensors, and the hybrid fiber structure is suitable for many multi-parameter measurement occasions and has important practical application significance.

On-Demand Optimization of Colorimetric Gas Sensors Using a Knowledge-Aware Algorithm-Driven Robotic Experimental Platform.

Synthesizing the best material globally is challenging; it needs to know what and how much the best ingredient composition should be for satisfying multiple figures of merit simultaneously. Traditional one-variable-at-a-time methods are inefficient; the design-build-test-learn (DBTL) method could achieve the optimal composition from only a handful of ingredients. A vast design space needs to be explored to discover the possible global optimal composition for on-demand materials synthesis. This research developed a hypothesis-guided DBTL (H-DBTL) method combined with robots to expand the dimensions of the search space, thereby achieving a better global optimal performance. First, this study engineered the search space with knowledge-aware chemical descriptors and customized multiobjective functions to fulfill on-demand research objectives. To verify this concept, this novel method was used to optimize colorimetric ammonia sensors across a vast design space of as high as 19 variables, achieving two remarkable optimization goals within 1 week: first, a sensing array was developed for ammonia quantification of a wide dynamic range, from 0.5 to 500 ppm; second, a new state-of-the-art detection limit of 50 ppb was reached. This work demonstrates that the H-DBTL approach, combined with a robot, develops a novel paradigm for the on-demand optimization of functional materials.