Carbon-Based Nanomaterials Decorated Electrospun Nanofibers in Biosensors: A Review

Nanomaterials have revolutionized scientific research due to their exceptional physical and chemical capabilities. Carbon-based nanomaterials such as graphene and its derivates have excellent electrical, optical, thermal, physical, and chemical properties that have made them indispensable in several industries worldwide, including medicine, electronics, and energy. By incorporating carbon-based nanomaterials as nanofillers in electrospun nanofibers (ESNFs), smoother and highly conductive nanofibers can be achieved that possess a large surface area and porosity. This approach provides a superior alternative to traditional materials in the development of improved biosensors. Carbon-based ESNFs, among the most exciting new-generation materials, have many applications, including filtration, pharmaceuticals, biosensors, and membranes. The electrospinning technique is a highly efficient and cost-effective method for producing desired nanofibers compared to other methods. Various types of natural and synthetic organic polymers have been successfully utilized in solution electrospinning to produce nanofibers directly. To create diagnostics devices, various biomolecules like antibodies, enzymes, aptamers, ligands, and even cells can be bound to the surface of nanofibers. Electrospun nanofibers can serve as an immobilization matrix to create a biofunctional surface. Thus, biosensors with desired features can be produced in this way. This study comprehensively reviews biosensors that integrate nanodiamonds, fullerenes, carbon nanotubes, graphene oxide, and carbon dots into electrospun nanofibers.

Recent Advances in the Recognition Elements of Sensors to Detect Pyrethroids in Food: A Review

The presence of pyrethroids in food and the environment due to their excessive use and extensive application in the agriculture industry represents a significant threat to public health. Therefore, the determination of the presence of pyrethroids in foods by simple, rapid, and sensitive methods is warranted. Herein, recognition methods for pyrethroids based on electrochemical and optical biosensors from the last five years are reviewed, including surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), chemiluminescence, biochemical, fluorescence, and colorimetric methods. In addition, recognition elements used for pyrethroid detection, including enzymes, antigens/antibodies, aptamers, and molecular-imprinted polymers, are classified and discussed based on the bioreceptor types. The current research status, the advantages and disadvantages of existing methods, and future development trends are discussed. The research progress of rapid pyrethroid detection in our laboratory is also presented.

Research Progress of Graphene-Based Materials on Flexible Supercapacitors

With the development of wearable and flexible electronic devices, there is an increasing demand for new types of flexible energy storage power supplies. The flexible supercapacitor has the advantages of fast charging and discharging, high power density, long cycle life, good flexibility, and bendability. Therefore, it exhibits great potential for use in flexible electronics. In flexible supercapacitors, graphene materials are often used as electrode materials due to the advantages of their high specific surface area, high conductivity, good mechanical properties, etc. In this review, the classification of flexible electrodes and some common flexible substrates are firstly summarized. Secondly, we introduced the advantages and disadvantages of five graphene-based materials used in flexible supercapacitors, including graphene quantum dots (GQDs), graphene fibers (GFbs), graphene films (GFs), graphene hydrogels (GHs), and graphene aerogels (GAs). Then, we summarized the latest developments in the application of five graphene-based materials for flexible electrodes. Finally, the defects and outlooks of GQDs, GFbs, GFs, GHs, and GAs used in flexible electrodes are given.

Non-Enzymatic Amperometric Glucose Sensor Based on Carbon Nanodots and Copper Oxide Nanocomposites Electrode

In this research work, a non-enzymatic amperometric sensor for the determination of glucose was designed based on carbon nanodots (C-dots) and copper oxide (CuO) nanocomposites (CuO-C-dots). The CuO-C-dots nanocomposites were modified on the surface of a screen-printed carbon electrode (SPCE) to increase the sensitivity and selectivity of the glucose sensor. The as-synthesized materials were further analyzed for physico-chemical properties through characterization tools such as transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR); and their electrochemical performance was also studied. The SPCE modified with CuO-C-dots possess desirable electrocatalytic properties for glucose oxidation in alkaline solutions. Moreover, the proposed sensing platform exhibited a linear range of 0.5 to 2 and 2 to 5 mM for glucose detection with high sensitivity (110 and 63.3 µA mM-1cm-2), and good selectivity and stability; and could potentially serve as an effective alternative method of glucose detection.

Review of Carbon and Graphene Quantum Dots for Sensing

Carbon and graphene quantum dots (CQDs and GQDs), known as zero-dimensional (0D) nanomaterials, have been attracting increasing attention in sensing and bioimaging. Their unique electronic, fluorescent, photoluminescent, chemiluminescent, and electrochemiluminescent properties are what gives them potential in sensing. In this Review, we summarize the basic knowledge on CQDs and GQDs before focusing on their application to sensing thus far followed by a discussion of future directions for research into CQDs- and GQD-based nanomaterials in sensing. With regard to the latter, the authors suggest that with the potential of these nanomaterials in sensing more research is needed on understanding their optical properties and why the synthetic methods influence their properties so much, into methods of surface functionalization that provide greater selectivity in sensing and into new sensing concepts that utilize the virtues of these nanomaterials to give us new or better sensors that could not be achieved in other ways.

Carbon-based quantum particles: an electroanalytical and biomedical perspective

Carbon-based quantum particles, especially spherical carbon quantum dots (CQDs) and nanosheets like graphene quantum dots (GQDs), are an emerging class of quantum dots with unique properties owing to their quantum confinement effect.

Graphene Quantum Dot-Aerogel: From Nanoscopic to Macroscopic Fluorescent Materials. Sensing Polyaromatic Compounds in Water

Fluorescence based on quantum confinement is a property restricted to the nanoscopic range. The incorporation of nanoparticles in a three-dimensional polymeric network could afford macroscopic scaffolds that show nanoscopic properties. Moreover, if these scaffolds are based on strong bonds, the stability of the resulting materials can be preserved, thus enhancing their final applications. We report for the first time the preparation of a graphene quantum dot (GQD) composite based on a cationic covalent network. This new material has unusual features: (i) the final composite remains stable after several swelling-deswelling cycles, thus demonstrating strong interactions between GQDs and the polymeric material, and therefore it could be used as a portable system. (ii) Fluorescence emission in the composite and in solution is quasi-independent to the excitation wavelength. (iii) However, and in contrast to the behavior observed in GQD solutions, the fluorescence of the composite remains unaltered over a wide pH range and in the presence of different ions commonly found in tap water. (iv) Fluorescence quenching is only observed as a consequence of molecules that bear aromatic systems, and this could be applied to the preparation of in situ water sensors.

Sensitive determination of rutin by spectrofluorimetry using carbon dots synthesized from a non-essential amino acid

The present study describes the synthesis of carbon dots (CDs) using a non-essential amino acid, asparagine as a precursor. The HR-TEM image shows that the size of the prepared CDs was 2.9±0.2nm with a spherical morphology. The UV-visible spectrum of CDs exhibits a major band at 307nm along with a shoulder band around 207nm corresponding to n-π* and π-π* transitions, respectively. Further, the CDs show emission maximum at 441nm when excited at 348nm. The synthesized CDs were then exploited for the determination of rutin by spectrofluorimetry based on the decrease in emission intensity at 441nm. It was found that emission intensity of CDs at 441nm was decreased while adding 0.5μM rutin to CDs. On the other hand, addition of other metal ions and anions including 5mM Mg²⁺, K⁺, Ca²⁺, Na⁺, NO₃^- and oxalate, 2.5mM Cu²⁺ and Fe³⁺ and 3mM glycine, glucose, histidine, proline and cysteine does not affect the emission intensity at 441nm. A good linearity was observed for the emission intensity against 0.5-15μM rutin with a correlation coefficient of 0.997 and the limit of detection was found to be 1×10^-7M (61μg/L) (S/N=3). The real sample analysis was done by determining rutin in a pharmaceutical sample.

Generation of a carbon dots/ammonium persulfate redox initiator couple for free radical frontal polymerization

We report a new redox initiator couple of ammonium persulfate (APS)/carbon dots (CDs) with high initiation efficiency used in frontal polymerization (FP).

Sustainable carbon-dots: recent advances in green carbon dots for sensing and bioimaging

This review article highlights recent progress in use of green precursors for synthesis of carbon-dots and their applications in fluorescence-based sensing and bioimaging.