Green synthesis of carbon quantum dots toward highly sensitive detection of formaldehyde vapors using QCM sensor

Ethylenediamine assist preparation of carbon dots with novel biomass for highly sensitive detection of levodopa

Levodopa (l-Dopa), a precursor drug for dopamine has been widely used to treat Parkinson's disease. However, excess accumulation of l-Dopa in the body may cause movement disorders and uncontrollable emotions. Therefore, it is vital to monitor l-Dopa levels in patients. In this study, a carbon dot (CD)-based fluorescence sensing system was developed for sensitive detection of l-Dopa. The CDs were prepared using a novel biomass, Pandanus amaryllifolius Roxb., as a carbon source via a simple hydrothermal method. Interestingly, it was found that ethylenediamine doping in the preparation system increased the quantum yield of CDs, as well as their fluorescence response sensitivity to l-Dopa. After optimizing the preparation and sensing conditions, the detection limit of l-Dopa decreased from 1.54 μM to 0.05 μM. A complete methodological validation was conducted and the probe was successfully applied to the determination of l-Dopa in fetal bovine serum with excellent precision (RSD ≤ 2.99%) and recoveries of 88.50-99.71%. Overall, this work provides an effective strategy for the regulation of properties of CDs derived from biomass and an innovative method for clinical l-Dopa monitoring.

Application of biomass carbon dots in food packaging

Since its discovery, carbon quantum dots (CDs) have been widely applied in cell imaging, drug delivery, biosensing, and photocatalysis due to their excellent water solubility, chemical stability, fluorescence stability biocompatibility, low toxicity, and preparation cost. However, the low fluorescence yield and poor surface structure limit the application of CDs. Heteroatom doping is considered an ideal method to improve CDs' optical and electrical properties. From this perspective, eco-friendly biomass and its derivatives are perfect carbon precursors for CDs because they contain the heteroatoms needed to modify CDs, and their complex chemical composition gives CDs a wide variety of surface functional groups. Besides, converting biomass waste into high-value-added CDs is also an innovation in biomass waste treatment. Therefore, this paper focuses on the carbon precursors of biomass CDs. At the same time, food packaging occupies an essential position in the industry, and fluorescent CDs with good fluorescence properties, high chemical stability, and good photobleaching properties have great application potential in packaging innovation techniques that have emerged in recent years, but relevant reports are scarce and scattered. Considering that the surface morphology, chemical structure, and optical and electrical properties of biomass CDs are primarily affected by the carbon precursors' chemical structure and preparation method, this paper also focuses on the synthesis method of biomass CDs and its application in anti-counterfeiting packaging, intelligent packaging, antioxidant packaging, and antibacterial packaging.

Portable sensing methods based on carbon dots for food analysis

Food analysis is significantly important in monitoring food quality and safety for human health. Traditional methods for food detection mainly rely on benchtop instruments and require a certain amount of analysis time, which promotes the development of portable sensors. Portable sensing methods own many advantages over traditional techniques such as flexibility and accessibility in diverse environments, real-time monitoring, cost-effectiveness, and rapid deployment. This review focuses on the portable approaches based on carbon dots (CDs) for food analysis. CDs are zero-dimensional carbon-based material with a size of less than 10 nm. In the manner of sensing, CDs exhibit rich functional groups, low biotoxicity, good biocompatibility, and excellent optical properties. Furthermore, there are many methods for the synthesis of CDs using various precursor materials. The incorporation of CDs into food science and engineering for enhancing food safety control and risk assessment shows promising prospects.

Recent Advances in Electrochemical Sensors for Formaldehyde

Formaldehyde, a ubiquitous indoor air pollutant, plays a significant role in various biological processes, posing both environmental and health challenges. This comprehensive review delves into the latest advancements in electrochemical methods for detecting formaldehyde, a compound of growing concern due to its widespread use and potential health hazards. This review underscores the inherent advantages of electrochemical techniques, such as high sensitivity, selectivity, and capability for real-time analysis, making them highly effective for formaldehyde monitoring. We explore the fundamental principles, mechanisms, and diverse methodologies employed in electrochemical formaldehyde detection, highlighting the role of innovative sensing materials and electrodes. Special attention is given to recent developments in nanotechnology and sensor design, which significantly enhance the sensitivity and selectivity of these detection systems. Moreover, this review identifies current challenges and discusses future research directions. Our aim is to encourage ongoing research and innovation in this field, ultimately leading to the development of advanced, practical solutions for formaldehyde detection in various environmental and biological contexts.

Novel ultra-sensitive and highly selective cyanine sensors based on solvent-free microwave synthesis for the detection of trace hypochlorite ions in drinking water

The adoption of chlorine in drinking water disinfection with the determination of residual chlorine in the form of hypochlorite ion (ClO-) is in widespread demand. Several sensors including colorimetric, fluorometric, and electrochemical methods are currently in use, but detection limits and ease of application remain a challenge. In this work, two new cyanine derivatives-based ClO- sensors, that were prepared by solvent-free microwave synthesis, are reported. The two sensors are highly sensitive and selective to ClO-, exhibiting a noticeable color change visible to the naked eye. Additionally, the sensors can detect ClO- without interference from other potential water pollutants, with low detection limits of 7.43 ppb and 0.917 ppb based on absorption performance. When using fluorometric methods, the sensors' detection limits are pushed down to 0.025 ppb and 0.598 ppb for sensors I and II, respectively. The sensors can be loaded with paper strips for field and domestic detection of ClO- in tap water treatment installations. Using the quartz crystal microbalance (QCM) technique, these sensors showed strong detection sensitivity to ClO-, with detection limits of 0.256 ppm and 0.09 ppm for sensors I and II, respectively. Quantum chemical studies using density functional theory (DFT) calculations, natural bond orbital (NBO) analysis, molecular electrostatic potential (MESP), and time-dependent density functional theory (TD-DFT) supported the findings. The sensing mechanism is rationalized in terms of radical cation formation upon ClO- oxidation of cyanine sensors I and II.

Influence of humidity on accuracy of QCM - IR780-based GUMBOS sensor arrays

Herein, hydrophobic coating materials are reported for QCM detection of VOCs under dry and humid conditions. In this study, IR780-based GUMBOS ([IR780][OTf] and [IR780][NTf2]) were synthesized using an ion exchange reaction and the anions trifluoromethanesulfonimide ([OTf]) and bisperfluoromethanesulfonimide ([NTf2]). The parent iodide salts and GUMBOS ([IR780][I]), [IR780][OTf], and [IR780][NTf2]) were characterized using several analytical techniques. These salts were then employed as sensor coatings on quartz crystal resonators using an electrospray coating method. These sensors were exposed to four flow ratios of five common VOCs in the absence and presence of 10 vol% water. Fundamental frequency responses were recorded and further employed as input variables to develop highly accurate multi-sensor arrays (MSAs). Accuracy was better than 78.3% without water, and better than 91.7% in the presence of water. When multi-harmonic responses were evaluated as input variables to assess discrimination ability for each sensor, highly accurate virtual sensor arrays (VSAs) were developed using each GUMBOS coating. In the case of [IR780][NTf2], a slight improvement in discrimination was achieved in the presence of water (95%) versus the absence of water. Moreover, this study highlights development of readily synthesized hydrophobic coatings of IR780-based GUMBOS for potential detection and discrimination of VOCs in aqueous systems.

Biofabrication of carbon quantum dots and their food packaging applications: a review

Carbon quantum dots (CQDs) are an emerging class of novel carbon nanomaterials (< 10 nm). These zero-dimensional CQDs have recently invoked significant interest due to their high fluorescence ability, strong electronic conductivity, biocompatibility, excellent chemical stability, non-toxicity, and environmental safety. Bio-fabrication of CQDs from organic resources remains attractive owing to their excellent functional properties. An emerging class of CQDs is fabricated by various conventional methods. However, these methods need many chemical agents and instrument facilities. Bio-fabrication of CQDs has a lot of benefits because of its simple fabrication and eco-friendly. Therefore, the green synthesized CQDs are considered optimistic candidates for developing novel functional materials for food packaging applications. Thus, it is important to investigate the latest update on green-based CQDs for food packaging applications. This current review paper discusses the physicochemical properties of CQDs, the bio-fabrication of CQDs, and the fluorescent properties of CQDs along with their food packaging applications.