Nanostructured Sensors Research Articles

Design of colorimetric nanostructured sensor phases for simple and fast quantification of low concentrations of acid vapors

Two colorimetric nanostructured sensor phases (Color-NSPs) for the determination of low concentrations of acid vapors in the atmosphere of paper storage rooms have been designed and characterized. The acid vapor determination is based on the color change that occurs in polyaniline (PANI) in the presence of acids when it goes from its emeraldine base form (blue) to its emeraldine salt form (green). To synthesize the Color-NSPs, two methods have been used, a one-step method performed by grafting polyaniline onto a cellulose membrane (Cellu-PANI) and a two-step method in which in the first step, polyaniline is grafted onto the surface of polymeric nanoparticles (NPs-PANI), and in a second step, NPs-PANI are immobilized into the pores of a nylon membrane (Nylon-NPs PANI). The response of the sensors versus acid vapor was measured by color coordinates with a photographic camera. A linear response range from 1 ppmv to 7 ppmv was found for both sensors, and the detection limits were 0.95 ppmv (1.2 % RSD) and 0.40 ppmv (0.8 % RSD) for Cellu-PANI and Nylon-NPs PANI, respectively. In addition, both sensors showed complete reversibility and a short exposition time (5 min). The potential applicability of the Color-NSPs in the control of the exposure of paper heritage collections to outdoor- and indoor-generated gaseous pollutants was demonstrated by determining acid vapors in museums. The method was validated with an external reference method; the paired test was applied, and p-values greater than 5% were obtained, indicating an excellent correlation and showing that the Color-NSPs reported are simple, fast, and an economical alternative to control and protect cultural heritage materials in indoor environments.Graphical

Label-Free Saliva Test for Rapid Detection of Coronavirus Using Nanosensor-Enabled SERS.

The recent COVID-19 pandemic has highlighted the inadequacies of existing diagnostic techniques and the need for rapid and accurate diagnostic systems. Although molecular tests such as RT-PCR are the gold standard, they cannot be employed as point-of-care testing systems. Hence, a rapid, noninvasive diagnostic technique such as Surface-enhanced Raman scattering (SERS) is a promising analytical technique for rapid molecular or viral diagnosis. Here, we have designed a SERS- based test to rapidly diagnose SARS-CoV-2 from saliva. Physical methods synthesized the nanostructured sensor. It significantly increased the detection specificity and sensitivity by ~ten copies/mL of viral RNA (~femtomolar concentration of nucleic acids). Our technique combines the multiplexing capability of SERS with the sensitivity of novel nanostructures to detect whole virus particles and infection-associated antibodies. We have demonstrated the feasibility of the test with saliva samples from individuals who tested positive for SARS-CoV-2 with a specificity of 95%. The SERS-based test provides a promising breakthrough in detecting potential mutations that may come up with time while also preparing the world to deal with other pandemics in the future with rapid response and very accurate results.

Enhanced toluene sensing performance of nanostructured aluminium-doped nickel oxide gas sensor

Enhanced toluene sensing performance of nanostructured aluminium-doped nickel oxide gas sensor

Alkali metals (Na, K) doped ZnO/CuO composite films for real-time tracking of sweat loss

Real-time sweat rate monitoring provides clinically proper directives for preventive medicine and disease diagnosis. This research represents an attempt to develop a semiconductor-based nanostructured sensor for monitoring sweat rate using a ZnO/CuO composite thin film. A series of alkali metals (sodium, Na; potassium, K) doped ZnO/CuO composite samples were fabricated on soda lime glass substrates by the Successive Ionic Layer Adsorption and Reaction method. The sweat solution sensing response characterization exhibited promising sensing behavior under room conditions. The Na- and K-doped samples showed a pronounced response at low and high concentrations of the sweat solution. While the undoped composite film responds to the high concentration sweat solution (117.90 mM) with a sensitivity of 4.10, this value increases up to 9.15 for the 2.0% Na-doped samples. In addition, the response time shortens from 6 s to 4 s for 2.0% Na substitutions. Pristine, 2.0% Na and 2.0% K-substituted ZnO/CuO composites exhibit great linearity with linear regression ranges, R2, of 0.958, 0.971, and 0.984, respectively. We concluded that doping of ZnO/CuO composites with alkali metals Na and K is a good candidate for real-time tracking of sweat loss as biological evidence.

Recent trends in nanostructured carbon-based electrochemical sensors for the detection and remediation of persistent toxic substances in real-time analysis

There are rising issues regarding the presence and discharge of emerging pollutants (EPs) in the ecosystem, including pharmaceutical waste, organic contaminants, heavy metals, pesticides, antibiotics and dyes. The human populace is typically exposed to a variety of EPs and toxins, such as those found in the soil, air, food supply, and drinkable water. Thus, creating new purification methods and effective pollution detection tools is a significant task. Several researchers globally have created unique analytical techniques including chromatography/mass and gaseous atomic absorption spectroscopy for the identification of contaminants to date. The aforementioned techniques have excellent sensitivity, but they are costly, time-consuming, costly, need sophisticated expertise to operate and are difficult to execute due to their enormous scale. Electrochemical sensors with resilience, specificity, sensibility, and real-time observations are thus been designed as a solution to the aforementioned shortcomings. The development of innovative systems to assures human and environmental protection has been aided by significant improvements in nanostructured carbon-based electrochemical sensor platforms. These platforms show enticing characteristics including excellent electrocatalytic operations, increased electrical conductance, and efficient surface region when compared to conventional methods. This paper intends to provide an analysis of low-cost nanostructured carbon-based electrochemical sensors from 2015 to 2022 that could detect and eradicate components of EPs from various origins. This review discusses the characteristics and uses of nanostructured carbon-based electrochemical sensors, which include carbon nanotubes, MXenes, carbon dots/graphene dots, graphene/graphene oxide, and other materials. These sensors are used to detect EPs such as heavy metal ions (Pb(II), Cd(II), Hg(II), etc), pharmaceutical waste, dyes and pesticides. Additionally, processing and characterization techniques, including differential-pulsed voltammograms, SW voltammograms, ultraviolet-visible spectroscopy, fluorescence, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and scanning electron microscopy (SEM) are discussed in detail to examine the prospects of these carbon-based electrochemical sensors and associated detection mechanisms. It is intended that this analysis would stimulate the development of new detection methods for protecting public health and restoring the environment.

Electrochemical study for simultaneous detection of procaine hydrochloride and its metabolite in biological samples using a nanostructured strong sensor

Electrochemical study for simultaneous detection of procaine hydrochloride and its metabolite in biological samples using a nanostructured strong sensor

Breaking sensitivity limits of QCM-D: An integrated nano-honeycomb sensor for characterization molecular interactions with lipid bilayers.

In the last few years Quartz Crystal Microbalance with Dissipation (QCM-D) emerged as an indispensable label-free method for monitoring formation of lipid bilayers on surfaces and assessing quality of the bilayers formed. QCM-D provides time-resolved data on mass and viscoelastic properties of molecular layers at the sensor surface and therefore is suitable for detecting vesicle adhesion, rupture, and spreading to form planar surface-supported bilayers. However, the small surface areas of QCM sensors impose severe limitation on mass sensitivity of the method. This is, perhaps, the main reason why QCM-D is rarely employed for studying lipid bilayer phase transitions and membrane binding events. To overcome these limitations, we have integrated the QCM sensor with an array of rigid honeycomb-packed anodic aluminum oxide (AAO) nanopores of ca. 25-80 nm in diameter and 2-10 μm in length by anodizing aluminum film deposited on the electrode surface. The resulting nanostructured QCM sensor increased surface area and improved sensitivity of the method by >100-fold. AAO-QCM electrode also provided a nanoscale template for self-assembly of lipid bilayers into nanotubular structures without any chemical attachment. We then employed such nanopore-confined bilayers to observe the main and more difficult to characterize pre-transition of membranes prepared from either pure 1,2-dimyristoyl-sn-glycerol-3-phosphocholine (DMPC) or 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) lipids. Observed changes in QCM frequency reflected variations in lipid density upon phase transitions and occurred at temperatures in agreement with literature data. The signal-to-noise ratio of the phase transition peaks increased by 300-fold when compared to conventional QCM-D sensors. To further explore potential applications of AAO-QCM-D, ethanol-induced biphasic effects of phospholipid bilayers were studied. High sensitivity of AAO-QCM electrodes makes the method highly attractive for developing biosensing applications based on detecting changes in lipid packing at the nanoscale.

Chemiresistive Polymer Percolation Network Gas Sensor Created with a Nanosphere Template

AbstractThe sensitivity and limits of detection (LOD) of chemiresistive gas sensors can often be improved by increasing the surface area of the sensing material that interacts with the analyte. This process is referred to as nanostructuring. Nanostructured polypyrrole (PPy) chemiresistive sensors for ammonia detection were created with the aid of a nanosphere template. Polystyrene nanospheres are deposited to form a template between interdigitated electrodes, and chronoamperometry is then used to grow PPy between the electrodes within the gaps of the nanospheres. The PPy growth is controlled to create electrical percolation networks. After removal of the nanospheres by dissolving them, the percolation behavior and sensing response of the nanostructured PPy sensors are investigated. The nanostructured percolation sensors show higher sensitivity and lower LOD to ammonia than percolation networks prepared without nanosphere templates. An optimal nanostructured ammonia percolation sensor with a chemiresistive sensitivity of 2.59 ± 0.20% ppm−1 and a LOD of 71 ± 6 ppb is obtained.

Synthesis, Structural and Sensor Properties of Nanosized Mixed Oxides Based on In2O3 Particles.

The paper considers the relationship between the structure and properties of nanostructured conductometric sensors based on binary mixtures of semiconductor oxides designed to detect reducing gases in the environment. The sensor effect in such systems is determined by the chemisorption of molecules on the surface of catalytically active particles and the transfer of chemisorbed products to electron-rich nanoparticles, where these products react with the analyzed gas. In this regard, the role is evaluated of the method of synthesizing the composites, the catalytic activity of metal oxides (CeO2, SnO2, ZnO), and the type of conductivity of metal oxides (Co3O4, ZrO2) in the sensor process. The effect of oxygen vacancies present in the composites on the performance characteristics is also considered. Particular attention is paid to the influence of the synthesis procedure for preparing sensitive layers based on CeO2-In2O3 on the structure of the resulting composites, as well as their conductive and sensor properties.

Greenhouse Gas Detection Based on Infrared Nanophotonic Devices

Most greenhouse gases come from biological activities and industry which will lead to global warming and show an impact on human life. With the need of green transformation of the global economic structure and seeking for higher quality of human life, the detection and management of greenhouse gases, as well as most hazardous gases in the environment, are increasingly demanding. Applications in different fields require sensors that can detect gas volume fractions with magnitudes from 10–9 to 10–4. Greenhouse gas detection plays an important role both in the agriculture and industry field. In this review, we first summarize the mechanism of several common gas detectors used currently. Then, the advantages of nanostructured gas sensors are discussed. Finally, the applications of infrared gas sensors based on nanophotonic devices are described in detail. This review has been an outlook on the future development of infrared gas sensors based on nanophotonic devices.

Environmental pollutant hydrogen sulphide and its detection – A brief review

Many incidences of toxic exposure have been linked to H2S, particularly in the natural gas and petroleum industries, coke ovens, landfills, tanneries, wastewater treatment, and paper mills. The physiological consequences of H2S are always dependent on the concentration and duration of exposure. H2S concentrations can cause a variety of serious health concerns, including throat and eye related problems, impaired memory, and a loss of reasoning. To monitor and control the risk associated with this gas in real time, researchers have spent decades inventing sensors with adequate/good/robust metrological properties and strong stability. From the standpoint of human and environmental health protection, this thorough analysis linked to the toxicity and harmful effects of H2S gas. In a range of sensor devices, nano-structured materials-based sensors seem to be a good substitute for the most common options, like electrochemical and optical sensors. In this review, we evaluate the performance of various H2S sensors in terms of main operational factors such as sensing material, sensitivity, sensor stability, response time, response time, detection limits, concentration range, and selectivity.

Advances in nanostructured material-based non-enzymatic electrochemical glucose sensors.

Non-enzymatic electrochemical sensors that use functional materials to directly catalyze glucose have shown great promise in diabetes management, food control, and bioprocess inspection owing to the advantages of high sensitivity, long-term stability, and low cost. Recently, in order to produce enhanced electrochemical behavior, significant efforts have been devoted to the preparation of functional materials with regular nanostructure, as it provides high specific surface area and well-defined strong active sites for electrochemical sensing. However, the structure-performance correlation in this field has not been reviewed thoroughly in the literature. This review aims to present a comprehensive report on advanced zero- to three-dimensional nanostructures based on the geometric feature and to discuss in depth their structural effects on enzyme-free electrochemical detection of glucose. It starts by illustrating the sensing principles of nanostructured materials, followed by a detailed discussion on the structural effects related to the features of each dimension. The structure-performance correlation is explored by comparing the performance derived from diverse dimensional architectures, which is beneficial for the better design of regular nanostructure to achieve efficient enzyme-free sensing of glucose. Finally, future directions of non-enzymatic electrochemical glucose sensors to solve emerging challenges and further improve the sensing performance are also proposed.

Application of Unconditioned Nanostructured Thermoplastic-Based Strain Gauge Sensor in Wearable Electronics

Wearable electronics is now revolutionizing the world of smart sensors offering tremendous solutions to a variety of applications that span from biomedical market to gaming and fashion sectors. In this scenario, physical sensors play a crucial role since they offer fast and reliable feedback on human motion, even for fine gestures, and can detect vital physiological parameters such as breathing and heart beating, while being able to be easily integrated into textile. Among wearable physical sensors, thermoplastic materials are utilized for their sensitivity and high stretchability. Moreover, these materials exhibit a good chemical resistance and implement low-cost manufacturing processes. In this work, we report a full characterization of a new thermoplastic nanocomposite material comparing its performances with and without preconditioning for strain up to 20%. Together with a measured gauge factor (GF) of about 10, sensors without preconditioning exhibit very good stability and they result to be a good candidate for wearable applications. We demonstrate this statement by analyzing the performance of a smart wristband prototype that integrates these strain gauges, obtaining very high performance of the sensors without prestrain in gesture recognition tasks with an accuracy and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${F}$ </tex-math></inline-formula> -score of about 94%.

Kojic acid exploring as an essential food additive in real sample by a nanostructure sensor amplified with ionic liquid

Kojic acid exploring as an essential food additive in real sample by a nanostructure sensor amplified with ionic liquid

Carbon coating of GaN nanostructures for enhanced sensitivity and selectivity of chemical vapours

The chemical vapour sensing behaviour of pristine gallium nitride (GaN) and variously carbon coated GaN (C-GaN) nanostructures towards polar protic (methanol, lactic acid, ammonia, water), polar aprotic (acetone) and apolar (toluene) analytes is investigated. The thickness of the carbon layer on GaN was controlled by using argon or nitrogen as carrier gases for toluene. TEM micrographs revealed dependence of the carbon layer on the carrier gas; with nitrogen (~2.6 ± 0.6 nm) leading to a thinner layer than argon (~3.4 ± 0.7 nm). Interestingly, chemical sensing performance studies showed that the carbon coating improved the sensitivity of GaN to polar protic analytes, especially to the toxic ammonia. Most importantly, enhanced sensitivity was observed for water molecules on the C-GaN based devices in comparison to water sensitivity on bare GaN devices. In contrast, the carbon coating was observed to have little or no influence on the sensitivity towards polar aprotic and apolar analytes. In summary, the study demonstrates the importance of coating GaN nanoparticles with a thin carbonaceous layer for enhanced room temperature sensitive and selective detection of chemical vapour analytes. • GaN and carbon coated GaN nanostructured resistive sensors were studied • Studied analytes were methanol, lactic acid, ammonia, water, acetone and toluene • Carbon coating improves sensitivity of GaN nanostructures to polar protic analytes • The sensors operate at room temperature

A novel nanostructured organic framework sensor for selective and sensitive detection of doxycycline based on fluorescence enhancement

It is critical for human health to develop sensitive and rapid analytical methods for detecting doxycycline (DOX) residues in food. This paper presents a novel metal-organic framework nanomaterial (Zn-MOF) based on dithiodiglycolic acid and its application in DOX detection by fluorescent probe method. Zn-MOF itself does not fluoresce. When DOX is added, the system exhibits strong fluorescence (100-fold) at 530 nm. The fluorescence intensity displayed an excellent linear relationship with DOX concentration with a detection limit of 2.7 nM. The reaction solution's fluorescence displayed a visible color shift from colorless to yellow that was concentration-dependent. A smartphone was used to detect DOX by recognizing the red, green, and blue values of the reaction solution and the corresponding test paper. The use of smartphones can speed up the detection process and streamline operations, offering a sensitive and visible method for the quantitative detection of DOX residues in actual samples. Interestingly, Zn-MOF can discriminate DOX from other tetracyclines with high selectivity. This material has been used successfully as a fluorescent probe to determine DOX in fish samples with an average spiked recovery of 94.6 % ∼ 95.1 %. The DOX levels in the measured perch samples were 1.25 ∼ 157 μg/kg. There are 2 batches of DOX exceeding the standard in 14 batches.

Cd doped ZnO nanorods for efficient room temperature NH3 sensing

We demonstrate room temperature (25 °C) and low temperature (≦100 °C) NH3 gas sensing properties of Cd-doped ZnO nanorods (NRs) synthesized by a low temperature (90 °C) hydrothermal method. Although, the Cd concentration in the growth solution was varied over a large range from 0 to 80 mol %, the maximum estimated Cd doping concentration in ZnO NRs was 0.5 at % (80 mol %). Structural analysis confirmed the successful doping of Cd in ZnO and microstructure investigation revealed the presence of single nanorod and flower like nanorods in the same ensemble whose dimensions reduced with the Cd doping concentration. Photoluminescence and Raman spectra analyses confirmed the increase of defect concentrations in ZnO NRs by Cd doping thereby enhancing the overall gas sensing. In response to NH3, the nanostructure sensors exhibited a gradual increase in the sensitivity with the Cd doping concentration where the 0.5 at % Cd-doped ZnO NRs showed the highest sensitivity with an enhancement of ∼9% (at 60 ppm NH3) as compared to the un-doped ZnO. The sensitivity continued to rise with the increase of temperature from 110% (25 °C), 120% (50 °C), 170% (75 °C) to 243% (100 °C) indicating a gigantic enhancement of ∼133% at 100 °C from 25 °C. The Cd-doped ZnO NRs also revealed superior specificity of detecting NH3 over NO2, and H2S even at room temperature.

Nano-Functionalized Electrochemical Sensors by Aerosol Jet Printing

In the latest years, hydrogen peroxide quantification gained a growing interest in many fields both in industry and in the clinical environment. Among the different available methods, electrochemical transducers are of particular interest thanks to their ease of fabrication, convenient integration with microfluidics and electronics and their time and cost-effectiveness. Despite these advantages, electrochemical transducers are affected by many metrological issues. In this work, the novel technique of Aerosol jet printing (AJP) is exploited to fabricate fully printed nanostructured electrochemical sensors for hydrogen peroxide detection. Two different carbon-based printable nanostructures, carbon nanotubes (CNTs) and graphene, are employed to conveniently modify with the same technique electrodes’ surfaces. The performances of the proposed design, production process and the different functionalization are explored and discussed. After a preliminary evaluation of the electrochemical characteristics of the printed devices, tests in hydrogen peroxide are carried on. Both materials present a limit of detections (LODs) and sensitivity comparable with the ones obtained in the literature, even though CNT better performs than graphene in terms of sensitivity (20 versus 2.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> mM−2). The latter presents however a signal-to-noise ratio (SNR) of 51.2 dB that outperforms the one of CNT (26.5 dB) and thus it has a better resistance against noise. Overall, both the evaluated nanostructures appear suitable to improve the metrological characteristics of printed electrochemical sensors and ease their spreading as environmental control devices, and diagnostic tools and assess quality in the industrial environment.

Micro-/Nano-Structured Biodegradable Pressure Sensors for Biomedical Applications.

The interest in biodegradable pressure sensors in the biomedical field is growing because of their temporary existence in wearable and implantable applications without any biocompatibility issues. In contrast to the limited sensing performance and biocompatibility of initially developed biodegradable pressure sensors, device performances and functionalities have drastically improved owing to the recent developments in micro-/nano-technologies including device structures and materials. Thus, there is greater possibility of their use in diagnosis and healthcare applications. This review article summarizes the recent advances in micro-/nano-structured biodegradable pressure sensor devices. In particular, we focus on the considerable improvement in performance and functionality at the device-level that has been achieved by adapting the geometrical design parameters in the micro- and nano-meter range. First, the material choices and sensing mechanisms available for fabricating micro-/nano-structured biodegradable pressure sensor devices are discussed. Then, this is followed by a historical development in the biodegradable pressure sensors. In particular, we highlight not only the fabrication methods and performances of the sensor device, but also their biocompatibility. Finally, we intoduce the recent examples of the micro/nano-structured biodegradable pressure sensor for biomedical applications.

Ag:Y2O3–SnO2 core-shell-based nanostructured sensor for achieving high ammonia sensing performance

Ag:Y2O3–SnO2 core-shell-based nanostructured sensor for achieving high ammonia sensing performance