Academic literature on the topic 'Chemical sensors, analytical instrumentation, optics, nanotechnology'

During recent decades, metal oxide semiconductors (MOS) have sparked more attention in various applications and industries due to their excellent sensing characteristics, thermal stability, abundance, and ease of synthesis. They are reliable and accurate for measuring and monitoring environmentally important toxic gases, such as NO2, NO, N2O, H2S, CO, NH3, CH4, SO2, and CO2. Compared to other sensing technologies, MOS sensors are lightweight, relatively inexpensive, robust, and have high material sensitivity with fast response times. Green nanotechnology is a developing branch of nanotechnology and aims to decrease the negative effects of the production and application of nanomaterials. For this purpose, organic solvents and chemical reagents are not used to prepare metal nanoparticles. On the contrary, the synthesis of metal or metal oxide nanoparticles is done by microorganisms, either from plant extracts or fungi, yeast, algae, and bacteria. Thus, this review aims at illustrating the possible green synthesis of different metal oxides such as ZnO, TiO2, CeO2, SnO2, In2O3, CuO, NiO, WO3, and Fe3O4, as well as metallic nanoparticles doping.

The current development of science and the contemporary market, combined with high demands from consumers, force manufacturers and scientists to implement new solutions in various industries, including the packaging industry. The emergence of new solutions in the field of intelligent packaging has provided an opportunity to extend the quality of food products and ensures that food will not cause any harm to the consumer’s health. Due to physical, chemical, or biological factors, the state of food may be subject to degradation. The degradation may occur because the packaging, i.e., the protective element of food products, may be damaged during storage, transport, or other logistic and sales activities. This is especially important since most food products are highly perishable, and the maintenance of the quality of a food product is the most critical issue in the entire supply chain. Given the importance of the topic, the main purpose of this article was to provide a general overview of the application of biosensors, sensors, and tags in intelligent packaging used for food products. A short history and the genesis of intelligent packaging are presented, and the individual possibilities of application of sensors, biosensors, gas sensors, and RFID tags, as well as nanotechnology, in the area of the packaging of food products are characterized.

With the development of nanotechnology, fluorescent silicon nanomaterials have been synthesized and applied in various areas. Among them, silicon quantum dots (SiQDs) are a new class of zero-dimensional nanomaterials with outstanding optical properties, benign biocompatibility, and ultra-small size. In recent years, SiQDs have been gradually utilized for constructing high-performance fluorescent sensors for chemical or biological analytes. Herein, we focus on reviewing recent advances in SiQD-based fluorescent biosensors from a broad perspective and discussing possible future trends. First, the representative progress for synthesizing water-soluble SiQDs in the past decade is systematically summarized. Then, the latest achievement of the design and fabrication of SiQD-based fluorescent biosensors is introduced, with a particular focus on analyte-induced photoluminescence (fluorescence) changes, hybrids of SiQDs with other materials or molecules, and biological ligand-modification methods. Finally, the current challenges and prospects of this field are highlighted.

Micro- and nanotechnology-enabled sensors have made remarkable advancements in the fields of biomedicine and the environment, enabling the sensitive and selective detection and quantification of diverse analytes. In biomedicine, these sensors have facilitated disease diagnosis, drug discovery, and point-of-care devices. In environmental monitoring, they have played a crucial role in assessing air, water, and soil quality, as well as ensured food safety. Despite notable progress, numerous challenges persist. This review article addresses recent developments in micro- and nanotechnology-enabled sensors for biomedical and environmental challenges, focusing on enhancing basic sensing techniques through micro/nanotechnology. Additionally, it explores the applications of these sensors in addressing current challenges in both biomedical and environmental domains. The article concludes by emphasizing the need for further research to expand the detection capabilities of sensors/devices, enhance sensitivity and selectivity, integrate wireless communication and energy-harvesting technologies, and optimize sample preparation, material selection, and automated components for sensor design, fabrication, and characterization.

The Sencell sensor uses glucose-induced changes in an osmotic pressure chamber for continuous glucose measurement. A final device shall have the size of a grain of rice. The size limiting factor is the piezo-resistive pressure transducers inside the core sensor technology (resulting chamber volume: 70 µL. To achieve the necessary miniaturization, these pressure transducers were replaced by small (4000 × 400 × 150 nm³) nano-granular tunneling resistive (NTR) pressure sensors (chamber volume: 750 nL). For benchmark testing, we filled the miniaturized chamber with bovine serum albumin (BSA, 1 mM) and exposed it repeatedly to distilled water followed by 1 mM BSA solution. Thereafter, we manufactured sensors with glucose testing chemistry (ConcanavalinA/dextran) and investigated sensor performance with dynamic glucose changes between 0 and 300 mg/dL. Evaluation of the miniaturized sensors resulted in reliable pressure changes, both in the BSA benchmark experiment (30–35 mBar) and in the dynamic in vitro continuous glucose test (40–50 mBar). These pressure results were comparable to similar experiments with the previous larger in vitro sensors (30–50 mBar). In conclusion, the NTR pressure sensor technology was successfully employed to reduce the size of the core osmotic pressure chamber by more than 95% without loss in the osmotic pressure signal.

On-site detection of chemical warfare agents (CWAs) can be performed by various analytical techniques. Devices using well-established techniques such as ion mobility spectrometry, flame photometry, infrared and Raman spectroscopy or mass spectrometry (usually combined with gas chromatography) are quite complex and expensive to purchase and operate. For this reason, other solutions based on analytical techniques well suited to portable devices are still being sought. Analyzers based on simple semiconductor sensors may be a potential alternative to the currently used CWA field detectors. In sensors of this type, the conductivity of the semiconductor layer changes upon interaction with the analyte. Metal oxides (both in the form of polycrystalline powders and various nanostructures), organic semiconductors, carbon nanostructures, silicon and various composites that are a combination of these materials are used as a semiconductor material. The selectivity of a single oxide sensor can be adjusted to specific analytes within certain limits by using the appropriate semiconductor material and sensitizers. This review presents the current state of knowledge and achievements in the field of semiconductor sensors for CWA detection. The article describes the principles of operation of semiconductor sensors, discusses individual solutions used for CWA detection present in the scientific literature and makes a critical comparison of them. The prospects for the development and practical application of this analytical technique in CWA field analysis are also discussed.

Colorimetric sensors have been widely used to detect numerous analytes due to their cost-effectiveness, high sensitivity and specificity, and clear visibility, even with the naked eye. In recent years, the emergence of advanced nanomaterials has greatly improved the development of colorimetric sensors. This review focuses on the recent (from the years 2015 to 2022) advances in the design, fabrication, and applications of colorimetric sensors. First, the classification and sensing mechanisms of colorimetric sensors are briefly described, and the design of colorimetric sensors based on several typical nanomaterials, including graphene and its derivatives, metal and metal oxide nanoparticles, DNA nanomaterials, quantum dots, and some other materials are discussed. Then the applications, especially for the detection of metallic and non-metallic ions, proteins, small molecules, gas, virus and bacteria, and DNA/RNA are summarized. Finally, the remaining challenges and future trends in the development of colorimetric sensors are also discussed.

After millions of years of evolution, biological chemical sensing systems (i.e., olfactory and taste systems) have become very powerful natural systems which show extreme high performances in detecting and discriminating various chemical substances. Creating field-effect sensors using biomaterials that are able to detect specific target chemical substances with high sensitivity would have broad applications in many areas, ranging from biomedicine and environments to the food industry, but this has proved extremely challenging. Over decades of intense research, field-effect sensors using biomaterials for chemical sensing have achieved significant progress and have shown promising prospects and potential applications. This review will summarize the most recent advances in the development of field-effect sensors using biomaterials for chemical sensing with an emphasis on those using functional biomaterials as sensing elements such as olfactory and taste cells and receptors. Firstly, unique principles and approaches for the development of these field-effect sensors using biomaterials will be introduced. Then, the major types of field-effect sensors using biomaterials will be presented, which includes field-effect transistor (FET), light-addressable potentiometric sensor (LAPS), and capacitive electrolyte–insulator–semiconductor (EIS) sensors. Finally, the current limitations, main challenges and future trends of field-effect sensors using biomaterials for chemical sensing will be proposed and discussed.

Gas detectors have attracted considerable attention for monitoring harmful gases and air pollution because of industry development and the ongoing interest in human health. On the other hand, conventional high−temperature gas detectors are unsuitable for safely detecting harmful gases at high activation temperatures. Photo−activated gas detectors improve gas sensing performance at room temperature and enable low−power operation. This review presents a timely overview of photo−activated gas detectors that use illuminated light instead of thermal energy. Illuminated light assists in gas detection and is classified as visible or ultraviolet light. The research on photo−activated gas detectors is organized according to the type of gas that can be intensively detected. In addition, a development strategy for advancing photo−activated gas detectors is discussed.

The contamination of the environment, accidental or intentional, in particular with chemical toxins such as industrial chemicals and chemical warfare agents has increased public fear. There is a critical requirement for the continuous detection of toxins present at very low levels in the environment. Indeed, some ultra-sensitive analytical techniques already exist, for example chromatography and mass spectroscopy, which are approved by the US Environmental Protection Agency for the detection of toxins. However, these techniques are limited to the detection of known toxins. Cellular expression of genomic and proteomic biomarkers in response to toxins allows monitoring of known as well as unknown toxins using Polymerase Chain Reaction and Enzyme Linked Immunosensor Assays. However, these molecular assays allow only the endpoint (extracellular) detection and use labels such as fluorometric, colorimetric and radioactive, which increase chances of uncertainty in detection. Additionally, they are time, labor and cost intensive. These technical limitations are unfavorable towards the development of a biosensor technology for continuous detection of toxins. Federal agencies including the Departments of Homeland Security, Agriculture, Defense and others have urged the development of a detect-to-protect class of advanced biosensors, which enable environmental surveillance of toxins in resource-limited settings. In this study a Surface-Enhanced Raman Spectroscopy (SERS) immunosensor, aka a SERS-linked immunosensor assay (SLISA), has been developed. Colloidal silver nanoparticles (Ag NPs) were used to design a flexible SERS immunosensor. The SLISA proof-of-concept biosensor was validated by the measurement of a dose dependent expression of RAD54 and HSP70 proteins in response to H2O2 and UV. A prototype microchip, best suited for SERS acquisition, was fabricated using an on-chip SLISA to detect RAD54 expression in response to H2O2. A dose-response relationship between H2O2 and RAD54 is established and correlated with EPA databases, which are established for human health risk assessment in the events of chemical exposure. SLISA outperformed ELISA by allowing RISE (rapid, inexpensive, simple and effective) detection of proteins within 2 hours and 3 steps. It did not require any label and provided qualitative information on antigen-antibody binding. SLISA can easily be translated to a portable assay using a handheld Raman spectrometer and it can be used in resource-limited settings. Additionally, this is the first report to deliver Ag NPs using TATHA2, a fusogenic peptide with cell permeability and endosomal rupture release properties, for rapid and high levels of Ag NPs uptake into yeast without significant toxicity, prerequisites for the development of the first intracellular SERS immunosensor.

The detection of various types of pollutants, toxins, and adulterants that are detrimental to the environment and human health is essential for monitoring air, water, soil, and food quality. Technologies that enable the detection and quantification of analytes at the point-of-need can enable decision makers to take timely and effective actions to minimize damage and avert widespread crisis. In recent years, different types of nanomaterials in conjunction with various sensing technologies have led to the creation of novel and highly sensitive analyte detection assays. Of these nanomaterials, fluorescent copper nanoparticles templated by dsDNA have garnered considerable research interest due to their low-cost, wide availability, and relative ease of synthesis. The analyte detection assays utilizing dsDNA-templated copper nanoparticles have the potential to be deployed in point-of-need settings as they do not involve complex procedures and generate results within a short period of time. However, there are a few challenges inherent to copper nanoparticle-based assays that prevent their use outside laboratory settings. The detection of the weak fluorescence emission from the nanoparticles requires the use of highly sensitive and expensive detectors. Further, the fluorescence emission intensity from the nanoparticles varies with time, making the technique sensitive to the time of measurement. Introducing specificity into analyte detection assays using these nanoparticles also remains a challenge. This thesis proposes techniques to address these challenges to facilitate the adaptation of copper nanoparticle-based fluorescence assays for point-of-need applications. Additionally, the thesis proposes three new analyte detection assays. Firstly, a chemical technique to improve the fluorescence properties of dsDNA-templated copper nanoparticles is proposed. When compared to conventional synthesis techniques, the proposed method achieves 11 times higher fluorescence signal intensity from the dsDNA-templated copper nanoparticles and 4 times faster attainment of maximum fluorescence signal. The utility of this enhancement strategy for analyte measurement is demonstrated through a novel assay for melamine detection from milk samples which could achieve a limit of detection of 0.1 ppm melamine. Utilizing the proposed fluorescence enhancement technique, a handheld fluorometer capable of detecting DNA-templated copper nanoparticles is developed. The fluorometer was constructed with low-cost, off-the-shelf components like a UV-LED and a PIN photodiode. The performance of the developed system is demonstrated through the detection of melamine in milk samples via the interference synthesis of copper nanoparticles. The developed fluorometer can easily be adapted to detect different types of analytes at the point-of-need and can be deployed as a screening tool for environmental and food quality testing. The fluorescence of copper nanoparticles decays within a few minutes making the quantitative estimation of analytes sensitive to the time of measurement. Despite the loss of fluorescence, the nanoparticles remain intact as evidenced by microscopy techniques like TEM and AFM. To overcome the issue of time sensitivity of fluorescence measurement, etched fibre Bragg grating (eFBG) sensors are presented as a detection/characterization tool for copper nanoparticles. The in-situ formation of the copper nanoparticles on the DNA template attached to the eFBG sensor causes a significant shift in the reflected Bragg wavelength signal. Moreover, the shift in the Bragg wavelength signal was found to be constant over time after the formation of copper nanoparticles was completed, thus overcoming the issue of time sensitivity. The application of the proposed eFBG sensors for analyte detection utilizing the interference synthesis of copper nanoparticles is also demonstrated. Finally, the use of aptamers to improve the specificity of copper nanoparticle-based assays is proposed. As the growth of the copper nanoparticles is template specific, there are several challenges in developing aptamer-templated copper nanoparticle assays. A method to use a fully hybridized aptamer-duplex as template for copper nanoparticle formation is proposed. A novel fluorescence assay using aptamer-duplex templated copper nanoparticles for the detection of lipopolysaccharides (LPS) is demonstrated. The proposed assay has a wide range of detection from 1-10^5 ng/ml and a limit of detection of 1 ng/ml LPS. The mechanism of the proposed assay was verified with the SYBR Green intercalating dye. This led to the development of an alternative assay for LPS detection using SYBR Green and the aptamer-duplex which was found to have a wide range of detection from 0.1-10^5 ng/ml and a limit of detection of 0.1 ng/ml LPS.