The demand for reliable and cost-effective CO2 gas sensors is escalating due to their extensive applications in various sectors such as food packaging, indoor air quality assessment, and real-time monitoring of anthropogenic CO2 emissions to mitigate global warming. Nanostructured materials exhibit exceptional properties, including small grain size, controlled morphology, and heterojunction effects, rendering them promising candidates for chemiresistive CO2 gas sensors. This review article provides an overview of recent advancements in chemiresistive CO2 gas sensors based on nanostructured semiconducting materials. Specifically, it discusses single oxide structures, metal-decorated oxide nanostructures, and heterostructures, elucidating the correlations between these nanostructures and their CO2 sensing properties. Additionally, it addresses the challenges and future prospects of chemiresistive CO2 gas sensors, aiming to provide insights into the ongoing developments in this field.

This chapter emphasizes the recent developments with the gas sensors based on two-dimensional (2D) MXene-based hybrid nanomaterials for the detection of various toxic gases. In the family of 2D materials, the new member, MXene has emerged as an outstanding gas sensing material due to its favorable characteristics like an abundance of interaction sites, metallic conductivity, tunable surface properties, bandgap, and excellent mechanical strength. Further, the ease of its solution processability and straightforward functionalization make it the choicest material for hybrids with different types of inorganic and organic nanomaterials. The synergic effect of MXene with these nanomaterials is found to enhance the response kinetics of the hybrid gas sensors. The synthesis of MXene-based nanohybrids, gas sensing kinetics, and sensing mechanisms of hybrid sensors have been elucidated in this chapter.

This work explores the use of ZIF-8, a metal–organic framework (MOF) material, for its use in the optical detection of volatile organic compounds (VOCs) in Fabry–Pérot and surface plasmon resonance (SPR)-based sensors. The experiments have been carried out with ethanol (EtOH) and show response times as low as 30 s under VOC-saturated atmospheres, and the estimated limit of detection is below 4000 ppm for both sensor types. The selectivity towards other VOCs is relatively poor, although the dynamics of adsorption/desorption differ for each VOC and could be used for selectivity purposes. Furthermore, the hydrophobicity of ZIF-8 has been confirmed and the fabricated sensors are insensitive to this compound, which is a very attractive result for its practical use in gas sensing devices.

Over the past couple of decades, the incidence of breast cancer (BC) has significantly increased among females in comparison to other cancer types. In medicinal terminology, the susceptibility to BC is mainly centered around three hormonal receptors: estrogen (ER), progesterone (PR), and human epidermal growth receptor (HER2). Notably, estrogen- dependent breast cancer has a considerable female demographic, making it treatable with hormonal drugs and less intensive immunotherapy. Conversely, the narrative delves into the ominous type of cancer known as triple-negative breast cancer (TNBC). The orientation of all three receptors falls in a negative direction, which is ineffective for treatments that rely on hormonal or antagonist medicaments. Therefore, the only option available to tackle this type of cancer is chemotherapy, which causes toxicity within the body, is highly expensive, and is non-targeted. To counter this challenge, researchers have pioneered nano-based drug delivery systems (NDDS) owing to their innumerable merits and scientific development. NDDS mainly involves polymeric nanoparticles, liposomes, and dendrimers. This review comprehensively details the advancements in nanoinduced targeted drug delivery systems, with a focus on surface modification techniques for active targeting, enhanced drug release, and improved pharmacokinetics. Critical analysis extends to preclinical and clinical studies, revealing the potential of nano-drug delivery systems in TNBC to surpass traditional therapies, with promising heightened efficacy and reduced side effects.

In this paper, we present a sensor that employs Zeolitic Imidazolate Frameworks (ZIF-8) on a Surface Plasmon Resonance sensor based on diffraction gratings to detect ethanol vapors via refractive index change in the porous structure.

Metal–organic frameworks (MOFs) are materials that feature a large surface area with permanent porosity, which is an attractive property for chemical and gas sensing, making them a good candidate for sensor fabrication. In this paper, we present a sensor that employs zeolitic-imidazolate-based MOFs (ZIF-8) to detect ethanol vapors via refractive index-dependent optical interference.

For the first time, the impact of water and metal-oxide nanoparticles (MONPs) on the electronic structure and optical properties of 1-ethyl-3-methylimidazolium methylsulfate (C2mim MS) ionic liquid (IL) is reported. Offswitching of cation-anion interaction and emergence of new peak at 2970 cm-1 was observed indicating change in the interaction strength and conformation of ethyl chain upon dilution. Optical absorption properties and viscosity of neat IL significantly enhanced by dispersing a very low volume fraction of MONPs. DFT calculations provide a clue of the formation of a protective layer of IL around NPs owing to simultaneous cationicanionic interaction with the MONPs.

Many people around the world are concerned about meat safety and quality, which has resulted in the ongoing advancement of packaged food technology. Since the emergence of graphene in 2004, the number of studies on layered two-dimensional materials (2DMs) for applications ranging from food packaging to meat quality monitoring has been expanding quickly. Recently, scientists have been working hard to develop a novel class of 2DMs that keep the good things about graphene but don't have zero bandgaps at room temperature. Much work has been done on layered transition metal dichalcogenides (TMDCs) like different metal sulfides and selenides for meat spoilage gas sensors. This review looks at (i) the main indicators of meat spoilage and (ii) the detection methods that can be used to find out if meat has been spoiled, such as chemiresistive, electrochemical, and optical methods. (iii) the role of 2DMs in meat spoilage detection and (iv) the emergence of advanced methods for selective classification of target analytes in meat/food spoilage detection in recent years. Thus, this review demonstrates the potential scope of 2DMs for developing intelligent sensor systems for food and meat spoilage detection with high viability, simplicity, cost-effectiveness, and other multipurpose tools.

Machine learning is increasingly used in the analysis of distinct types of data for clinical diagnosis and monitoring the environment, particularly because of the large amounts of data generated in sensing and biosensing methods. In this chapter, we discuss the usage of machine learning for electrochemical sensors, with emphasis on colorimetric principles of detection

In this article, the potential of solution-processed spinel nickel-cobaltite (NiCo2O4) nanostructures as chemiresistive sensors for detecting ethanol (C2H5OH) is demonstrated. Various techniques were used to characterize the structure, composition, and morphology of the as-synthesized NiCo2O4 samples prior to gas sensing studies. By adjusting the reaction time, cubic crystalline NiCo2O4 structures with different surface morphologies were obtained, including upright-standing nanoplatelets enclosed by nanoneedle-type structures. These nanoneedle-type structures are composed of numerous interconnected nanoparticles with diameters of ∼4–8 nm. These unique structural and morphological characteristics enable the NiCo2O4 nanostructures to exhibit excellent sensing properties towards C2H5OH gas at 140 °C, with significant changes in their resistance values observed upon exposure to 10–1000 ppm C2H5OH. Notably, the NiCo2O4 sample processed for 9 hours, with a specific surface area of 48.19 m2/g, was recognized as the most promising sensor among the various NiCo2O4 samples, showing a maximum response of 54.4% towards 200 ppm C2H5OH, with good repeatability and complete recovery characteristics. Additionally, we also investigated and discussed various sensing characteristics of the NiCo2O4 sensors, including their gas concentration dependent response, selectivity, temperature dependent response, reproducibility and stability. Moreover, the sensing interactions between NiCo2O4 and C2H5OH gas molecules were elucidated through the use of an energy band diagram, providing valuable insights into the sensing mechanism of these sensors. Overall, this research provides a practical and simple strategy for synthesizing spinel oxide nanostructures and demonstrates their potential in C2H5OH sensing applications.

The current pandemic of the acute severe respiratory syndrome coronavirus 2 (SARS-CoV-2) killed about 6.4 million and infected more than 600 million individuals by august of 2022, and researchers worldwide are searching for fast and selective approaches for this virus detection. Colorimetric biosensors are an excellent alternative because they are sensitive, simple, fast, and low-cost for rapid detection of SARS-CoV-2 compared to standard Enzyme-linked immunosorbent assay (ELISA) and Polymerase Chain Reaction (PCR) techniques. This study systematically searched and reviewed literature data related to colorimetric biosensors in detecting SARSCoV-2 viruses, recovered from the Scopus (n = 16), Web of Science (n = 19), PubMed (n = 19), and Science Direct (n = 17) databases totalizing n = 71 articles. Data were analyzed for the type of nanomaterial, biorecognition material at the detection limit (LOD), and devices designed for diagnostics. The most applied nanomaterial were gold nanoparticles, in their original form and hybrid in quantum dots and core-shell. In addition, we show high specificity in point-of-care (POC) diagnostic devices as a faster and cheaper alternative for clinical diagnosis. Finally, the highlights of the colorimetric biosensor developed for diagnostic devices applied in swabs, surgical masks, and lateral flow immunoassays were presented.

The great progresses witnessed in the last decade for the rational design of the graphitic carbon nitride (g-C3N4) have warranted its successful use in applications including sensing, photocatalysis, electromagnetic shielding and energy storage devices. There have been multiple studies for g-C3N4 (or g-CN) nanostructures that have underlined the substantial research as a photocatalyst and electrode material in energy devices, while no such in-depth study, on the other hand, went into detail about the g-CN based sensors, their underlying problems regarding the transduction principles, and sensitivity/selectivity issues towards various analytes. Although in its nascent stage, the g-CN nanostructures have made the detection possible in almost all environmental entities (land, air, and water), e.g., biomolecules (protein, glucose, melamine, amino acids) and engineered compounds (drugs, antibiotics, explosives), yet a systematic study summarizing the merits/demerits for g-CN based sensors is still missing. This review gives a detailed overview and summarizes the challenges while simultaneously highlights the key insights in the exciting field of sensors. Researchers working in the sensor domain will undoubtedly benefit from this review, as it will provide new perspectives into the intriguing world of g-CN material which has emerged as a new sensing platform that is at-par to other functional materials discussed in the literature. (C) 2022 Elsevier B.V. All rights reserved.

Magnetic field sensing plays vital role in vast range of areas such as navigation, military, and biomedical sciences. In recent times, optical sensors have made great advances, resulting in the development of magnetic field sensors based on optical principles due to their non-susceptibility to electromagnetic interference. Here, a simple and inexpensive approach for sensing magnetic field, that converts the magnetic field into a mechanical translation (of the sensing element) and then change into optical signals is presented. These optical signals are speckle patterns generated using a laser beam reflected off an optically rough metal cantilever which is exposed to the magnetic field. Magnetic field is quantified by measuring the changes in the speckle pattern using the intensity correlation technique. The approach can measure the static and time varying magnetic fields. The proposed system has a resolution of 2.2 mu T and can measure magnetic fields with less than a 2% error.

MoS2 nanoflowers were fabricated and deposited on porous graphite felt (MoS2-GF) via the hydrothermal treatment to activate peroxydisulfate (PDS) for water disinfection. The surface textural and chemical characterization indicated that the MoS2 nanoflowers were successfully grown on the graphite felt. MoS2-activated PDS oxidation with 0.25 g/L MoS2 and 0.2 mM PDS achieved above 7-log removal of E. coli within contact time of 25 min. Gram-negative bacteria (E. coli and P. aeruginosa) were more sensitive to the oxidation reactions than the Gram-positive ones (E. faecalis and S. aureus) due to their larger cell sizes and thinner wall thicknesses. The live/dead backlight staining experiments and scanning electron microscopy characterization revealed that the bacteria were inactivated via cell membrane damage. The free radical quenching experiments suggested that the SO4 center dot-, center dot OH, and center dot O2- were the main reactive radicals involved into bacteria inactivation. The MoS2-activated PDS oxidation also achieved undetectable heterotrophic plate count for real river water lake water within contact time of 120 min.

Salmonella bacteria is a foodborne pathogen found mainly in food products causing severe symptoms in the individual, such as diarrhea, fever, and abdominal cramps after consuming the infected food, which can be fatal in some severe cases. Rapid and selective methods to detect Salmonella bacteria can prevent outbreaks when ingesting contaminated food. Nanobiosensors are a highly sensitive, simple, faster, and lower cost method for the rapid detection of Salmonella, an alternative to conventional enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) techniques. This study systematically searched and analyzed literature data related to nucleic acid-based nanobiosensors (NABs) with nanomaterials to detect Salmonella in food, retrieved from three databases, published between 2010 and 2021. We extracted data and critically analyzed the effect of nanomaterial functionalized with aptamer or DNA at the limit of detection (LOD). Among the nanomaterials, gold nanoparticles (AuNPs) were the most used nanomaterial in studies due to their unique optical properties of the metal, followed by magnetic nanoparticles (MNPs) of Fe3O4, copper nanoparticles (CuNPs), and also hybrid nanomaterials multiwalled carbon nanotubes (c-MWCNT/AuNP), QD/UCNP-MB (quantum dotes upconverting nanoparticle of magnetic beads), and cadmium telluride quantum dots (CdTe QDs@MNPs) showed excellent LOD values. The transducers used for detection also varied from electrochemical, fluorescent, surface-enhanced Raman spectroscopy (SERS), RAMAN spectroscopy, and mainly colorimetric due to the possibility of visualizing the detection result with the naked eye. Furthermore, we show the magnetic separation system capable of detecting the target amplification of the genetic material. Finally, we present perspectives, future research, and opportunities to use point-of-care (POC) diagnostic devices as a faster and lower cost approach for detecting Salmonella in food as they prove to be viable for resource-constrained environments such as field-based or economically limited conditions.

Low temperature, microcube-shaped zinc stannate (ZnSnO3) nanostructures using a low-power microheater sensor platform to detect NO2 gas with high sensitivity and selectivity.

Biosensors are a simple, low-cost, and reliable way to detect pesticides in food matrices to ensure consumer food safety. This systematic review lists which nanomaterials, biorecognition materials, transduction methods, pesticides, and foods have recently been studied with biosensors associated with analytical performance. A systematic search was performed in the Scopus (n = 388), Web of Science (n = 790), and Science Direct (n = 181) databases over the period 2016–2021. After checking the eligibility criteria, 57 articles were considered in this study. The most common use of nanomaterials (NMs) in these selected studies is noble metals in isolation, such as gold and silver, with 8.47% and 6.68%, respectively, followed by carbon-based NMs, with 20.34%, and nanohybrids, with 47.45%, which combine two or more NMs, uniting unique properties of each material involved, especially the noble metals. Regarding the types of transducers, the most used were electrochemical, fluorescent, and colorimetric, representing 71.18%, 13.55%, and 8.47%, respectively. The sensitivity of the biosensor is directly connected to the choice of NM and transducer. All biosensors developed in the selected investigations had a limit of detection (LODs) lower than the Codex Alimentarius maximum residue limit and were efficient in detecting pesticides in food. The pesticides malathion, chlorpyrifos, and paraoxon have received the greatest attention for their effects on various food matrices, primarily fruits, vegetables, and their derivatives. Finally, we discuss studies that used biosensor detection systems devices and those that could detect multi-residues in the field as a low-cost and rapid technique, particularly in areas with limited resources.