Oxide Dots Research Articles

Enhanced electron transfer kinetics via constructing co-catalytic system of cerium oxide and carbon dots enabling efficient electrosynthesis of hydrogen peroxide in neutral media

The sluggish kinetics coupled with the competition of four-electron pathway in neutral media diminishes the production efficiency of hydrogen peroxide (H2O2) via the two-electron oxygen reduction reaction (2e− ORR). To address this dilemma, this contribution proposes one electron modulation strategy to expedite the charge transfer capability by integrating carbon dots with CeO2 (CDs/CeO2) for the efficient neutral electrosynthesis of H2O2. It was found that the integration could effectively bolster both the activity and selectivity of 2e− ORR on CDs and CeO2. Remarkably, the highest 2e− selectivity could reach up to 92 % for the optimized CDs/CeO2, substantially surpassing that (77 %) of pristine CeO2, together with about 1.5 times enhancement of activity. Meanwhile, it also delivered a superior long durability at 20 mA cm−2 for 24 h and a high Faraday efficiency of 97 %. Further in-situ transient potential scanning (TPS) technique revealed that the pseudo-capacitance and charge storage capacity of CeO2 were significantly tuned by CDs during dynamic ORR process, being conducive to the reaction kinetics and the 2e− selectivity. The findings in this work not only extends the co-catalytic system based on CDs and rare earth materials for 2e− ORR, but also offers novel insights into correlation between their electron distribution dynamics and 2e− ORR performance.

A glassy carbon electrode modified with gold decorated iron oxide/ carbon dots for light assisted voltammetric detection of antibiotic resistant microbe Enterococcusfaecalis

Detecting bacteria is essential in managing significant health concerns as it enables timely intervention, reducing complications and improving patient outcomes, particularly in treating common infections that necessitate precise identification for effective symptom management. Enterococcus species represent a notable threat in hospital-acquired infections and urinary tract infections (UTIs), given the increasing prevalence of strains resistant to multiple antibiotics, unresponsive to standard therapies, and carrying various virulence factors. Traditional approaches to identifying Enterococcus faecalis (E. faecalis) have limitations, including prolonged processing times, limited sensitivity, and the potential for false positive results. While Polymerase Chain Reaction (PCR) is a valuable tool, it is susceptible to contamination and variations in DNA concentration. The emerging technique of Photoelectrochemical (PEC) holds promise for enhancing E. faecalis detection by leveraging photogenerated electrons and holes. This study introduces a rapid and precise approach utilizing a light-assisted electrochemical biosensor featuring a glassy carbon electrode modified with a nanocomposite of gold-coated iron oxide and carbon dots (Au@Fe3O4/CDs). The nanocomposite was successfully synthesized and underwent thorough characterization. The investigation has a detection range from 1 to 14 CFU mL−1, along with a notably low limit of detection (LOD: 3 CFU mL−1, LOQ: 10 CFU mL−1). Rigorous examination of real-world samples such as food, water, and soil demonstrated exceptional specificity, reproducibility, and long-term stability of the sensor. The applications of the Au@Fe3O4/CDs nanocomposite in PEC processes underscore the potential of this innovative approach in addressing health concerns associated with bacterial infections and delivering real-time impacts for both healthcare and environmental domains.

WITHDRAWN: Recent advances on the metal oxides and nanocomposites based on quantum dots and metal oxides for supercapacitor applications: A mini-review

Considering the limited resources of fossil fuels and the environmental pollution caused by their use, the need for alternative technology has become a global challenge. As a candidate for replacing fossil fuels, batteries have limitations such as the lack of sodium and lithium sources. Supercapacitors are a suitable alternative technology due to the availability of electrode materials. In this study, our team reviewed the supercapacitor performance of metal oxides and nanocomposites based on metal oxides and quantum dots to overcome the limitations of metal oxide electrode materials. In this study, by investigating the supercapacitor performance of nanocomposites based on metal oxide and quantum dots in three categories of carbon quantum dot, graphene quantum dot, and polymer dot, the performance of each quantum dot in improving the supercapacitor behavior of metal oxides was discussed. The results confirmed that the synergistic effect of quantum dots and metal oxides is improving the supercapacitor performance of nanocomposites. Also, the functional groups on the surface of the quantum dots accelerate the rate of penetration of ions and the rate of ion transfer. The results of this study confirmed that polymer dots have better performance among quantum dots with polymer properties and quantum dots properties at the same time which provides research opportunities for researchers in the field of supercapacitors.

Machine learning approaches to predict adsorption performance of sugarcane derived-carbon dot −based composite in the removal of dyes

This study presents a sustainable and low-cost approach to uniformly blend nanofillers (TiO2) and CDs) into chitosan polymer matrices, aiming to enhance the adsorption capacity and regeneration efficiency of the composite. The effect of degree of deacetylation on the composite was examined using crosslinkers EDA and ECH, achieving a DD of 78.8 % and demonstrating improved chemical and thermal stability compared to chitosan alone. Furthermore, SEM, TEM, and EDX mapping confirmed successful dispersion of nanofillers within the crosslinked chitosan matrix, with excellent adsorption performance towards cationic and anionic dyes (1666.67 mg/g and 1630 mg/g, respectively). The study also presents a novel approach that employs machine learning techniques to accurately predict optimization results. This study combines experiments and AI techniques using Python and machine learning algorithms on a dataset of over 600 experiments, achieving high forecast accuracy with the Random Forest model, evidenced by an R2 value of 1 and the lowest mean squared error for both dyes. The adsorption process followed Freundlich and the pseudo-second-order model. The statistical physical model explained a mixed orientation of anionic dye molecules and a multi-molecular mechanism of cationic dye molecules over nanocomposite, with FTIR results indicating electrostatic attraction, π-π interaction, and hydrogen bonding as key factors in the adsorption process. The composite material used in the study showed a consistent ability to adsorb dyes over 5 regeneration cycles in the column adsorption study, indicating its reusability. The results of this comprehensive investigation contribute to advancing sustainable wastewater treatment through the development of innovative nanocomposites and the use of sophisticated modelling techniques.

High surface area microporous carbon nanocubes from controlled processing of graphene oxide nanoribbons

A new, facile, and template-free method to prepare high surface area microporous carbon nanocubes (CNCs) from a mixture of graphene oxide nanoribbons (NRs), graphene oxide, and carbon dots is reported. The nanoribbons, approximately 30 nm wide and with lengths ranging from a few tens of nanometres up to several micrometres, were obtained from the oxidation of Black Pearls 2000 carbon black in nitric acid solution. The non-purified nanoribbons further contained additional fragments of graphene oxide, and of graphene oxide quantum dots. Slow pyrolysis of the nanoribbon mixture with slow heating rates, e.g., 3 °C/min, yielded carbon nanocubes approximately 250 nm in size with surface areas greater than 900 m2/g. Heating rates of 50 °C/min led to carbons with ∼800 m2/g surface area but bulk morphology. Precipitating the nanoribbons in potassium hydroxide solution, followed by carbonization, yielded microporous nanoparticle aggregates that were 20 nm in size with surface areas greater than 2000 m2/g. The particles exhibited complex, quasi-spherical morphology. Pyrolysis of other products obtained from oxidation in HNO3 of different grades of carbon black, specifically graphene oxide nanoparticles and quantum dots, yielded high surface area microporous carbons but with bulk morphology regardless of the processing conditions. Despite the lower surface area and pore volume of the CNCs in comparison to the nanospheres, the former contained ultramicropores that were highly accessible to CO2 as a molecular probe and had excellent selectivity of CO2 over N2. Hence, CNC materials have promising properties for applications where particle surface-to-volume ratios, high internal surface areas, and abundant super and ultramicropores are desired.

A Virtual Fabrication and High-Performance Design of 65 nm Nanocrystal Floating-Gate Transistor

Floating-gate transistor lies at the heart of many aspects of semiconductor applications such as neural networks, analog mixed-signal, neuromorphic computing, and especially in nonvolatile memories. The purpose of this paper was to design a high-performance nanocrystal floating-gate transistor in terms of a large memory window, low power, and extraordinary erasing speeds. Besides, the transistor achieves a thin thickness of the tunnel gate oxide layer. In order to obtain the high-performance design, this work proposed a set of structure parameters for the device such as the tunnel oxide layer thickness, Interpoly Dielectric (IPD), dot dimension, and dot spacing. Besides, this work was successful in the virtual fabrication process and methodology to fabricate and characterize the 65 nm nanocrystal floating-gate transistor. Regarding the results, while the fabrication process solves the limitation of the tunnel oxide layer thickness with the small value of 6 nm, the performance of the transistor has been significantly improved, such as 2.8 V of the memory window with the supply voltage of ±6 V at the control gate. In addition, the operation speeds are compatible, especially the rapid erasing speeds of 2.03 μs, 28.6 ns, and 1.6 ns when the low control gate voltages are ±9 V, ±12 V, and ±15 V, respectively.

Co-catalyst design to control charge transfer and product composition for photocatalytic H2 production and biomass reforming

Pt co-catalyst results in strong H2 evolution and piece-by-piece peeling of xylose; Ag co-catalyst results in cleavage of C2–C3 bond.

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.

Nitrogen and sulfur functionalized microporous carbon nanomaterial derived from waste coconut husk for the efficient detection and removal of ofloxacin

This study uses waste coconut husk to synthesize carbon quantum dots decorated graphene-like structure for sustainable detection and removal of ofloxacin. The XRD spectrum shows the carbon nanomaterial's layered structure with turbostratic carbon stacking on its surface. The FESEM and HRTEM studies claim the successful development of quantum dots decorated 2D layered structure of carbon nanomaterial. The functionalization of sulfur and nitrogen is well observed and studied through XPS, while Raman spectra have provided insight into the surface topology of the as-synthesized nanostructure. The BET surface area was found to be 1437.12 m2/g with a microporous structure (pore width 2.0 nm) which interestingly outcompete many reported carbon-based nanomaterials such as graphene oxide, reduced graphene oxide and quantum dots. The detection and removal processes are monitored through UV–visible spectroscopy and the obtained detection limit and adsorption capacity were 2.7 nM and 393.94 mg/L respectively. Additionally, 1 mg carbon nanomaterial has removed 49 % ofloxacin from water in just 1 h. In this way, this study has successfully managed the coconut husk waste after its utilization for environmental remediation purposes.

Application of Nanoparticles in Cancer Treatment: A Concise Review.

Timely diagnosis and appropriate antitumoral treatments remain of utmost importance, since cancer remains a leading cause of death worldwide. Within this context, nanotechnology offers specific benefits in terms of cancer therapy by reducing its adverse effects and guiding drugs to selectively target cancer cells. In this comprehensive review, we have summarized the most relevant novel outcomes in the range of 2010-2023, covering the design and application of nanosystems for cancer therapy. We have established the general requirements for nanoparticles to be used in drug delivery and strategies for their uptake in tumor microenvironment and vasculature, including the reticuloendothelial system uptake and surface functionalization with protein corona. After a brief review of the classes of nanovectors, we have covered different classes of nanoparticles used in cancer therapies. First, the advances in the encapsulation of drugs (such as paclitaxel and fisetin) into nanoliposomes and nanoemulsions are described, as well as their relevance in current clinical trials. Then, polymeric nanoparticles are presented, namely the ones comprising poly lactic-co-glycolic acid, polyethylene glycol (and PEG dilemma) and dendrimers. The relevance of quantum dots in bioimaging is also covered, namely the systems with zinc sulfide and indium phosphide. Afterwards, we have reviewed gold nanoparticles (spheres and anisotropic) and their application in plasmon-induced photothermal therapy. The clinical relevance of iron oxide nanoparticles, such as magnetite and maghemite, has been analyzed in different fields, namely for magnetic resonance imaging, immunotherapy, hyperthermia, and drug delivery. Lastly, we have covered the recent advances in the systems using carbon nanomaterials, namely graphene oxide, carbon nanotubes, fullerenes, and carbon dots. Finally, we have compared the strategies of passive and active targeting of nanoparticles and their relevance in cancer theranostics. This review aims to be a (nano)mark on the ongoing journey towards realizing the remarkable potential of different nanoparticles in the realm of cancer therapeutics.

An in-vitro study on post-surgical breast wound healing activity by zinc oxide dots and its optimization using Box Behnken design

The development of effective treatments for post-surgical malignant wounds caused by recurrent breast cancer remains challenging. This study aimed to address this issue by creating a biocompatible fluorescent quantum dot using curcumin-loaded Zinc oxide bionanocomposite (Cur-ZnOBC). The ZnOBC was combined with neem essential oil-Aloe-vera gel complex to produce the nanoconjugate Cur-ZnOBC, which was then transformed into curcumin-based quantum dots (Cur-ZnOQDs) using a microwave-assisted method to enhance drug delivery function. The Box-Behnken design was used to optimize the concentration variables involved in the formation of Cur-ZnOQDs. The synthesized Cur-ZnOQDs were found to have low cytotoxicity to human breast cancer cells and exhibited wound healing activity in malignant wounds of breast cancer cells post-surgery. Cell death was noticed only at a concentration of 0.6 mg/mL, and the wound closure area increased from 22.3% to 44.2% at 48 h, which was 20 times greater than the control. Therefore, Cur-ZnOQDs at lower concentration range may act as bio-enhancers to improve outcomes associated with breast cancer and ultimately improve the survival rate.

Magnetic graphene oxide carbon dot nanocomposites as an efficient quantification tool against parabens in water and cosmetic samples.

A new method is developed for the simultaneous detection and extraction of parabens, including methyl paraben (MP), ethyl paraben (EP), propyl paraben (PP), and butyl paraben (BP), based on magnetic graphene oxide carbon dot nanocomposites (Fe3O4@GO@CD). Fe3O4@GO@CD has been synthesized using one pot hydrothermal method by intercalating iron oxide and carbon dots between the layers of graphene oxide. Fe3O4@GO@CD was applied as the magnetic solid phase sorbent for the simultaneous extraction and detection of parabens from water (tap and river water) and cosmetic samples (hair serum and sunscreen cream). MP was measured at concentration of 0.25-0.26ng/mL in hair serum, while PP at 0.32-0.33ng/mL in sunscreen cream. Notably, good recoveries (88.74-98.03%; RSD = 2.31-6.88%) for river and tap water with detection limit of 0.039-0.046ng/mL were attained. The method has good cyclability up to 16 cycles and was highly repeatable. All these findings suggest that the Fe3O4@GO@CD would be potential sorbent for the analysis of parabens.

WO3·0.33H2O/carbon quantum dots hybrid nanostructures for efficient electrochemical hydrogen evolution reaction

Low-cost electrocatalysts with good catalytic performance are highly desirable for the sustainable production of hydrogen in order to meet the growing global energy crisis. In this work, WO3·0.33H2O/casein-derived carbon quantum dots hybrid nanostructures were synthesized via hydrothermal synthesis route utilizing casein-derived carbon quantum dots and precursor salts of WO3, and its electrochemical performance as an HER electrocatalyst was investigated. XRD, FESEM, TEM, SAED, XPS, FTIR, and Raman analyses confirmed the structural and compositional features of the WO3·0.33H2O/carbon quantum dots hybrid nanostructures. The electrochemical studies showed an efficient HER activity for WO3·0.33H2O/carbon quantum dots hybrid nanostructure with a low overpotential of 197 mV and a small Tafel slope of 101 mV/dec. The synergic effect of the hydrated tungsten oxide and carbon dots enhanced the conductivity and number of accessible active sites, promoting better mass transport, which was responsible for better HER activity. This work presents a cost-effective and green strategy to develop WO3·0.33H2O/carbon quantum dots hybrid nanostructures as a suitable electrocatalyst for hydrogen production.

Elucidating the mechanism of photocatalytic reduction of bicarbonate (aqueous CO2) into formate and other organics

The photocatalytic reduction of CO2 under solar irradiation is an ideal approach to mitigating global warming, and reducing aqueous forms of CO2 that interact strongly with a catalyst (e.g., HCO3−) is a promising strategy to expedite such reductions. This study uses Pt-deposited graphene oxide dots as a model photocatalyst to elucidate the mechanism of HCO3− reduction. The photocatalyst steadily catalyzes the reduction of an HCO3− solution (at pH = 9) containing an electron donor under 1-sun illumination over a period of 60 h to produce H2 and organic compounds (formate, methanol, and acetate). H2 is derived from solution-contained H2O, which undergoes photocatalytic cleavage to produce •H atoms. Isotopic analysis reveals that all of the organics formed via interactions between HCO3− and •H. This study proposes mechanistic steps, which are governed by the reacting behavior of the •H, to correlate the electron transfer steps and product formation of this photocatalysis. This photocatalysis achieves overall apparent quantum efficiency of 27% in the formation of reaction products under monochromatic irradiation at 420 nm. This study demonstrates the effectiveness of aqueous-phase photocatalysis in converting aqueous CO2 into valuable chemicals and the importance of H2O-derived •H in governing the product selectivity and formation kinetics.

Asymmetric and zinc-ion hybrid supercapacitors based on iron oxide and carbon dots

There is an urgent need to design and develop materials for high-performance electrochemical energy storage systems. This paper presents practical synthesis and novel combination of α-Fe2O3, carbon dots (CDs), and BiOCl for high performance asymmetric supercapacitors (ASCs) and zinc-ion hybrid supercapacitors (ZHSCs). The materials prepared by wet-chemical methods were probed with different analytical techniques. X-Ray Diffraction, Fourier Transform Infrared Spectroscopy) and Raman analyzes indicate presence of alkyl and aryl rich surface functional groups of CDs which contribute to conducive interface for the interplay between electrolyte and electrodes. The α-Fe2O3@CDs enabled ~20 fold increase in the electrochemical performance; 3686 F g−1 at a current density of 1 A g −1 in 2 M KOH electrolyte. However, the maximum specific capacitance of pristine α-Fe2O3 was just 184 F g−1 at the same current density. ASCs and ZHSCs were then fabricated using α-Fe2O3@CDs as the cathode along with anodes composed of BiOCl and Zn foil, respectively. The assembled ASC device achieved the potential window of 1.8 V with a high specific capacitance of 251 F g−1 at a current density of 1 A g−1. The highest energy, and power densities were 28 Wh kg−1 and 14.8 kW kg−1, respectively. The formed ZHSC exhibited the maximum specific capacitance of 449 F g−1 at a current density of 1 A g−1 with 78 % retention after 15,000 cycles. ZHSC outperformed ASC in terms of the energy and power density by ~5 (140 Wh kg−1) and ~ 2 (30 kW kg−1) times, respectively. These results position α-Fe2O3@CDs as an extremely promising material for ASCs and ZHSCs.

CuC(O) Interfaces Deliver Remarkable Selectivity and Stability for CO2 Reduction to C2+ Products at Industrial Current Density of 500mA cm-2.

The electrocatalytic CO2 reduction reaction (CO2 RR) is an attractive technology for CO2 valorization and high-density electrical energy storage. Achieving a high selectivity to C2+ products, especially ethylene, during CO2 RR at high current densities (>500mA cm-2 ) is a prized goal of current research, though remains technically very challenging. Herein, it is demonstrated that the surface and interfacial structures of Cu catalysts, and the solid-gas-liquid interfaces on gas-diffusion electrode (GDE) in CO2 reduction flow cells can be modulated to allow efficient CO2 RR to C2+ products. This approach uses the in situ electrochemical reduction of a CuO nanosheet/graphene oxide dots (CuOC(O)) hybrid. Owing to abundant CuOC interfaces in the CuOC(O) hybrid, the CuO nanosheets are topologically and selectively transformed into metallic Cu nanosheets exposing Cu(100) facets, Cu(110) facets, Cu[n(100) × (110)] step sites, and Cu+ /Cu0 interfaces during the electroreduction step, the faradaic efficiencie (FE) to C2+ hydrocarbonswasreached as high as 77.4% (FEethylene ≈ 60%) at 500mA cm-2 . In situ infrared spectroscopy and DFT simulations demonstrate that abundant Cu+ species and Cu0 /Cu+ interfaces in the reduced CuOC(O) catalyst improve the adsorption and surface coverage of *CO on the Cu catalyst, thus facilitating CC coupling reactions.

Apoptotic pathway protein expression variance in metal oxide and quantum dot treated HeLa cells.

Using the HeLa cell line as a cancerous model, apoptotic protein expression was assessed upon various nanoparticle treatments. Utilizing a known chemotherapeutic agent, cisplatin, as a positive control for induction of apoptosis, several metal oxides (ZnO and CuO) and quantum dots (CdSe/ZnS and InP/ZnS) were investigated for their ability to express apoptotic markers. ZnO, CuO, green CdSe/ZnS, and green InP/ZnS were treated for 24 hours at their IC50 value. Western blot techniques were used to measure protein expression of phosphorylated p53 (ser15), PUMA, and p21 which are involved in signal transduction of apoptosis. CuO, ZnO, and CdSe/ZnS demonstrated considerable p53 activation at 24 hrs compared to the non-treated control. At the IC50 value, CdSe/ZnS quantum dots were the quickest at activating p53 by phosphorylation at the Serine 15 residue. Together, our results provide new insight into the apoptotic mechanism behind these treatments and lead to improved treatments against cancer.

Concise nanotherapeutic modality for cancer involving graphene oxide dots in conjunction with ascorbic acid.

Cancer cells tend to have higher intracellular reactive oxygen species (ROS) levels and are more vulnerable to ROS-generating therapies such as ascorbic acid (H2Asc) therapy, whose potency has been explored by several clinical trials. However, its efficiency is restricted by the requirement of pharmacologically high local H2Asc concentrations. Here, we show that nitrogen-doped graphene oxide dots (NGODs), which are highly crystalline and biocompatible, can serve as a catalytic medium for improving H2Asc cancer therapy at orally achievable physiological H2Asc concentrations. NGODs catalyze H2Asc oxidation for H2O2 and dehydroascorbic acid generation to disrupt cancer cells by consuming intracellular glutathione (GSH) and inducing ROS damage. This is the first study to demonstrate the direct consumption of GSH using a carbon-based nano-catalyst (NGODs), which further expedites tumor killing. In addition, as in our previous study, NGODs can also serve as a highly efficient photosensitizer for photodynamic therapy. Under illumination, NGODs produce a considerable amount of H2O2 in the presence of physiological levels of H2Asc as a hole scavenger and further enhance the therapeutic efficiency. Thus, a concise nanotherapeutic modality could be achieved through the conjunction of multifunctional NGODs and H2Asc to selectively eliminate deep-seated and superficial tumors simultaneously (under 65% of normal cell viability, it kills almost all cancer cells). Note that this level of therapeutic versatility generally requires multiple components and complex manufacturing processes that run into difficulties with FDA regulations and clinical applications. In this study, the concise NGOD-H2Asc nanotherapeutic modality has demonstrated its great potential in cancer therapy.

Molecularly Imprinted Polymer-Coated Inorganic Nanoparticles: Fabrication and Biomedical Applications.

Molecularly imprinted polymers (MIPs) continue to gain increasing attention as functional materials due to their unique characteristics such as higher stability, simple preparation, robustness, better binding capacity, and low cost. In particular, MIP-coated inorganic nanoparticles have emerged as a promising platform for various biomedical applications ranging from drug delivery to bioimaging. The integration of MIPs with inorganic nanomaterials such as silica (SiO2), iron oxide (Fe3O4), gold (Au), silver (Ag), and quantum dots (QDs) combines several attributes from both components to yield highly multifunctional materials. These materials with a multicomponent hierarchical structure composed of an inorganic core and an imprinted polymer shell exhibit enhanced properties and new functionalities. This review aims to provide a general overview of key recent advances in the fabrication of MIPs-coated inorganic nanoparticles and highlight their biomedical applications, including drug delivery, biosensor, bioimaging, and bioseparation.

Simultaneous Detection of Neurotransmitters Using Carbon Nanomaterials

Glassy carbon electrodes cleaned and electrochemically pretreated in PBS were compared to electrodes modified with carbon black, graphene oxide, and carbon dots in terms of possibility of detection of neurotransmiters. We provide systematic studies regarding the detection of five neurobiologically relevant species: dopamine, serotonin, epinephrine, norepinephrine, and 3,4-dihydroxyphenylacetic acid on those four types of electrodes. We also evaluated the possibility of simultaneous detection of dopamine and serotonin in the presence of high levels of uric and ascorbic acids.Dopamine and serotonin are easily detected at carbon surfaces but unfortunately at a similar potential. Polymerization of dopamine, resulting in sensitivity loss is another problem, when measurements are carried out in cell culture medium or even in model solutions at physiological pH. Norepinephrine and epinephrine are both products of dopamine metabolism. Their structure includes an o-hydroquinone, which upon oxidation and the transfer of two electrons transforms into o-quinone. Additional chemical reactions may occur resulting in e.g. cyclization of the chain containing the epinephrine’s amino group and subsequent additional quinone-hydroquinone reactions of this product. DOPAC is the product of dopamine deamination. In neutral pH, its oxidation is partially irreversible. As in case of dopamine, side reactions can lead to film formation on the electrode surface. It is considered an interferent in determining dopamine levels.Detection in the presence of acids has proven possible on all three types of electrode modifications, although with different resolution. We evaluated sensitivity in terms of current density per active area of the sensor. In this way graphene oxide exhibited the highest sensitivity towards all tested neurotransmitters, whereas chemically functionalized carbon nanodots significantly increased oxidation peaks’ resolution. A considerable shift of signals towards more negative potentials for epinephrine, norepinephrine, and 3,4-dihydroxyphenylacetic acid was observed for all modifications as compared with glassy carbon electrodes. Analytical parameters obtained for each type of modification are resumed in Tab. 1 (dopamine), Tab. 2 (serotonin) and Tab.3 (epinephrine and norepinephrine).As shown in this and other works electrode pretreatment has a huge impact on the recorded signal. Thus it is sometimes hard to compare materials tested by different research groups. The same procedure of electrochemical pretreatment was in this work applied to coated and uncoated glassy carbon electrodes. The pretreatment allowed for partial cleaning of polymerized dopamine.Authors would like to thank The National Centre for Research and Development, Poland, for funding under grants LIDER/38/0138/L-9/17/NCBR/2018 and LIDER/33/0117/L-9/17/NCBR/2018. EWN would like to also thank the Foundation for Polish Science (FNP), from which she was supported through START programme and National Science Centre Poland for the MINIATURA grant NCN 2017/01/X/ST4/00463 Figure 1