Simultaneous electrochemical determination of ascorbic acid, dopamine and uric acid with helical carbon nanotubes

PEI-based functional materials: Fabrication techniques, properties, and biomedical applications

Cationic polymers have recently attracted considerable interest as research breakthroughs for various industrial and biomedical applications. They are particularly interesting due to their highly positive charges, acceptable physicochemical properties, and ability to undergo further modifications, making them attractive candidates for biomedical applications. Polyethyleneimines (PEIs), as the most extensively utilized polymers, are one of the valuable and prominent classes of polycations. Owing to their flexible polymeric chains, broad molecular weight (MW) distribution, and repetitive structural units, their customization for functional composites is more feasible. The specific beneficial attributes of PEIs could be introduced by purposeful functionalization or modification, long service life, biocompatibility, and distinct geometry. Therefore, PEIs have significant potential in biotechnology, medicine, and bioscience. In this review, we present the advances in PEI-based nanomaterials, their transfection efficiency, and their toxicity over the past few years. Furthermore, the potential and suitability of PEIs for various applications are highlighted and discussed in detail. This review aims to inspire readers to investigate innovative approaches for the design and development of next-generation PEI-based nanomaterials possessing cutting-edge functionalities and appealing characteristics.

Universal Single-Step Approach to the Immobilization of Cyclodextrins in a Supercritical Medium for Capturing Drug, Dye, and Metal Nanoclusters

By utilizing nanoreactor-like structures, the immobilization of macromolecules such as calixarenes and cyclodextrins (CD) with bucket-like structures provides new possibilities for engineered surface-molecule systems. The practical use of any molecular system depends on the availability of a universal procedure for immobilizing molecules with torus-like structures on various surfaces while maintaining identical operating parameters. There are currently several steps, including toxic solvent-based approaches using modified β-CD to covalently attach to surfaces with multistep reactions. However, the existing multistep process results in molecular orientation, restricts the accessibility of the hydrophobic barrel of β-CD's for practical use, and is effectively unable to use the surfaces immobilized with β-CD for a variety of applications. In this study, it was demonstrated that β-CD attached to the oxide-based semiconductor and metal surfaces through a condensation reaction between the hydroxyl-terminated oxide-based semiconductor/metal oxide and β-CD in supercritical carbon dioxide (SCCO₂) as a medium. The primary benefit of SCCO₂-assisted grafting of unmodified β-CD on various oxide-based metal and semiconductor surfaces is that it is a simple, efficient, one-step process and that it is ligand-free, scalable, substrate-independent, and uses minimal energy. Various physical microscopy and chemical spectroscopic methods were used to analyze the grafted β-CD oligomers. The application of the grafted β-CD films was demonstrated by the immobilization of rhodamine B (RhB), a dye, and dopamine, a drug. The in situ nucleation and growth of silver nanoclusters (AgNCs) in the molecular systems were studied for antibacterial and tribological properties by utilizing the guest-host interaction ability of β-CD.

Different Aspects of the Voltammetric Detection of Vitamins: A Review

Vitamins comprise a group of organic chemical compounds that contribute significantly to the normal functioning of living organisms. Although they are biosynthesized in living organisms, some are also obtained from the diet to meet the needs of organisms, which is why they are characterized as essential chemical compounds. The lack, or low concentrations, of vitamins in the human body causes the development of metabolic dysfunctions, and for this reason their daily intake with food or as supplements, as well as the control of their levels, are necessary. The determination of vitamins is mainly accomplished by using analytical methods, such as chromatographic, spectroscopic, and spectrometric methods, while studies are carried out to develop new and faster methodologies and techniques for their analysis such as electroanalytical methods, the most common of which are voltammetry methods. In this work, a study is reported that was carried out on the determination of vitamins using both electroanalytical techniques, the common significant of which is the voltammetry technique that has been developed in recent years. Specifically, the present review presents a detailed bibliographic survey including, but not limited to, both electrode surfaces that have been modified with nanomaterials and serve as (bio)sensors as well as electrochemical detectors applied in the determination of vitamins.

Ultraflexible PEDOT:PSS/Helical Carbon Nanotubes Film for All-in-One Photothermoelectric Conversion

Photothermoelectric (PTE) conversion can achieve the recovery of low-quality light or heat efficiently. Much effort has been devoted to the exploitation of the inorganic heterogeneous asynchronous (separate) PTE conversion system. Here, a full organic PTE film with a pseudobilayer architecture (PBA) according to the homogeneous synchronous (all-in-one) PTE conversion hypothesis was prepared via successive drop-casting a PEDOT:PSS/helical carbon nanotube (HCNT) mixture and PEDOT:PSS onto a vacuum ultraviolet treated substrate. Our results prove that the heptagon-pentagon pairs embedded in HCNTs promote a denser arrangement of the molecular chains of PEDOT, which enhances the crystallinity and affects the thermoelectric properties. The weak connection and hollow structure of HCNTs inhibit the dissipation of heat, and the zT value of the film reaches over 0.01. The PBA film shows better photothermal conversion performance than a neat PEDOT:PSS film and stably generates a temperature difference of over 25.68 °C without external cooling. A flexible PTE chip demo was manufactured, and the ideal open-circuit voltage (simulated via COMSOL) of that reaches over 1.5 mV under weak NIR stimulation (83.12 mW/cm2), which is the best value reported for an organic all-in-one PTE device, and the real maximum output power reaches 2.55 nW (166.01 mW/cm2). The chip has incredible ultraflexibility, and its inner resistance changes less than 1.42% after 10000 bending cycles and displays ultrahigh stability (similarity >90%) in a continuous periodic output. Our work fills the deficit of homogeneous synchronous PTE research for a PEDOT:PSS composite and is a preliminary attempt in an ultraflexible integrated all-in-one PTE chip design.

C/Sn deposition on a helical carbon nanofiber matrix as a high performance anode for lithium-ion batteries

C/Sn/HCNF composites were successfully prepared by solution phase synthesis and carbon thermal reduction. Within the hybrid composite, the HCNFs, Sn and carbon layer show a synergistic effect in improving coulombic efficiency and electrical capacity.

Polypyrrole/Helical Carbon Nanotube Composite with Marvelous Photothermoelectric Performance for Longevous and Intelligent Internet of Things Application

Helical carbon nanotube (HCNT) is a vital member of carbon nanomaterials, but little effort was devoted to explore its unique characteristics and applications during the past few decades. Here, we report an organic thermoelectric composite with an excellent photothermoelectric (PTE) effect by conformally wrapping polypyrrole (PPy) on the intricate surface of HCNTs, which have been confirmed to have remarkable near-infrared (NIR) photothermal conversion capability and ultralow heat transportation characteristics. The results indicate that with the increasing HCNT content, PPy shell thickness reduces and exhibits denser as well as partial orientation, while the inter-ring angle slowly decreases and the bipolaron becomes dominant in carrier composition gradually. Consequently, the Seebeck coefficient increases monotonically, whereas the electrical conductivity remains nearly invariant. The final composite combines the benign thermoelectric properties, excellent photothermal response performance, and the lowest thermal conductivity of the carbon-based thermoelectric composite yet reported (0.064 W m^-1 K^-1). A single strip NIR light-stimulated adjustable delay switch was designed and fabricated, with the open-circuit voltage and short-circuit current under a 400 mW cm^-2 NIR-stimulated approach to 720 μV and 62 nA with the discrepancy of consecutive periodic output signals less than 4.2%, exhibiting incredible stability and reliability and demonstrating the highest output voltage of a single strip among the reported organic PTE composite at room temperature. Our work fills in a gap of HCNT research, which hitherto existed in the PTE and thermoelectric field.

Sweet potato derived three-dimensional carbon aerogels with a hierarchical meso-macroporous and branching nanostructure for electroanalysis

In this paper, sweet potatoes (Ipomoea batatas) are used as low-cost precursors to synthesize carbon aerogels with a hierarchical meso-macroporous and branching nanostructure (HMM-BNCA). An HMM-BNCA-modified glassy carbon electrode (GCE) (HMM-BNCA/GCE) exhibits high electrocatalytic activity for some electroactive biomolecules. For ascorbic acid (AA), the HMM-BNCA/GCE exhibits low oxidation peak potential and detection limit (-0.005 V and 0.45 μM, S/N = 3), high sensitivities (195.43 and 121.00 μA mM-1 cm-2) and wide linear ranges (10-1250 μM and 1250-4750 μM), which are superior to those obtained at the GCE and carbon nanotube (CNT)-modified GCE (CNT/GCE). The HMM-BNCA/GCE exhibits significant resistance to fouling and the interfering substances for the detection of AA. The successful and accurate detection of AA in real samples (such as vitamin C injections and vitamin C soft drinks) in this work demonstrates the feasibility and tremendous potential of HMM-BNCA/GCE for the analysis of AA in complex systems.

Electrochemical dopamine sensor based on the use of a thermosensitive polymer and an nanocomposite prepared from multiwalled carbon nanotubes and graphene oxide

An electrochemical dopamine sensor with a temperature-controlled switch was constructed by using a mixture of thermo-sensitive block copolymers (type tBA-PDEA-tBA), graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs). If the temperature is below 26 °C, the polymer on the glassy carbon electrode (GCE) is stretched, the distance between the MWCNTs is large, and the charge transfer resistance (R_ct) of the composite also is large. In the presence of dopamine, the electron transfer at the electrode is strongly retarded and in the "off" state. At above 38 °C, the polymer is shrunk and the R_ct is much smaller. The presence of dopamine results in a rapid electron transfer at the GCE, and this is referred to as the "on" state. At temperatures between 26 and 38 °C, the polymer shrinks slightly and has a "spring-like" state. There is a linear relationship between the response current (typically measured at a potential as low as 0.16 V vs. Ag/AgCl) and temperature. The response to dopamine is linear in the 0.06 to 4.2 μM and 4.2 to 18.2 μM concentration range, and the detection limit is 42 nM. Conceivably, this approach provides a novel approach towards the design of electrochemical sensors based on the use of thermo-sensitive polymers. Graphical abstract Schematic presentation of reversible and temperature-controlled electrochemical response of dopamine on the thermo-sensitive block copolymers (tBA-PDEA-tBA) / multi-walled carbon nanotubes (MWCNTs) / graphene oxide (GO) / glassy carbon electrode (GCE).

Multiwalled carbon nanotube-based nanosensor for ultrasensitive detection of uric acid, dopamine, and ascorbic acid

A novel multiwalled carbon nanotube (MWCNT) based sensor was fabricated as a highly precise and stable electrochemical sensor. The synthesized sensor which consists of ZnNi bimetallic nanoalloy called the ZnNi NPs@f-MWCNT sensor, have been used for the simultaneous detection of uric acid (UA), dopamine (DA) and ascorbic acid (AA). The ZnNi NPs@f-MWCNT sensor obtained based on the microwave irradiation process, and its characterization was performed by using several physical techniques such as XRD, XPS, TEM, Raman, etc. The characterization showed that this sensor has excellent properties such as rich pore channels, excellent structural durability, and large surface area. These properties facilitated mass transfer and electron conductions. It was observed that the obtained sensor gave high electrochemical activity and wide linear responses (0.3-1.1 mM AA, 0.2-1.2 mM DA, 0.2-1.1 mM UA) in the detection of uric acid (UA), dopamine (DA) and ascorbic acid (AA). In addition to these properties, it has been found that the sensor has excellent anti-interferents properties towards AlCl₃, KCl₃, glucose, etc. and ZnNi NPs@f-MWCNT sensor was further applied to determine uric acid (UA), dopamine (DA) and ascorbic acid (AA) in real samples.

Simultaneous determination of ascorbic acid and caffeine in commercial soft drinks using reversed-phase ultraperformance liquid chromatography

A new reversed-phase ultraperformance liquid chromatography method with a photodiode array detector was developed for the quantification of ascorbic acid (AA) and caffeine (CAF) in 11 different commercial drinks consisting of one energy drink and 10 ice tea drinks. Separation of the analyzed AA and CAF with an internal standard, caffeic acid, was performed on a Waters BEH C₁₈ column (100 mm × 2.1 mm, 1.7 μm i.d.), using a mobile phase consisting of acetonitrile and 0.2M H₃PO₄ (11:89, v/v) with a flow rate of 0.25 mL/min and an injection volume of 1.0 μL. Calibration graphs for AA and CAF were computed from the peak area ratio of AA/internal standard and CAF/internal standard detected at 244.0 nm and 273.6 nm, respectively. The developed reversed-phase ultraperformance liquid chromatography method was validated by analyzing standard addition samples. The proposed reversed-phase ultraperformance liquid chromatography method gave us successful results for the quantitative analysis of commercial drinks containing AA and CAF substances.

Synthesis of carbon nanoparticle embedded graphene for sensitive and selective determination of dopamine and ascorbic acid in biological fluids

We have prepared carbon nanoparticle embedded graphene (CNEG) by carbonizing a ternary composite of GO/melamine-formaldehyde resin/Zn(OAc)₂.

Recent trends in carbon nanomaterial-based electrochemical sensors for biomolecules: A review

Carbon nanomaterials are advantageous for electrochemical sensors because they increase the electroactive surface area, enhance electron transfer, and promote adsorption of molecules. Carbon nanotubes (CNTs) have been incorporated into electrochemical sensors for biomolecules and strategies have included the traditional dip coating and drop casting methods, direct growth of CNTs on electrodes and the use of CNT fibers and yarns made exclusively of CNTs. Recent research has also focused on utilizing many new types of carbon nanomaterials beyond CNTs. Forms of graphene are now increasingly popular for sensors including reduced graphene oxide, carbon nanohorns, graphene nanofoams, graphene nanorods, and graphene nanoflowers. In this review, we compare different carbon nanomaterial strategies for creating electrochemical sensors for biomolecules. Analytes covered include neurotransmitters and neurochemicals, such as dopamine, ascorbic acid, and serotonin; hydrogen peroxide; proteins, such as biomarkers; and DNA. The review also addresses enzyme-based electrodes that are used to detect non-electroactive species such as glucose, alcohols, and proteins. Finally, we analyze some of the future directions for the field, pointing out gaps in fundamental understanding of electron transfer to carbon nanomaterials and the need for more practical implementation of sensors.

Co9S8 hollow spheres for enhanced electrochemical detection of hydrogen peroxide

This work reports on an experimental investigation of Co9S8 hollow spheres with excellent interfacial charge transfer ability for the electrochemical detection of hydrogen peroxide and glucose in alkaline environment. The result reveals that the Co9S8 hollow spheres exhibit excellent electrocatalytic activity for the reduction of hydrogen peroxide. An electrochemical sensor based on Co9S8 can be further realized, exhibiting a linear response range from 0.0001 to 11.11mM for hydrogen peroxide with a low detection limit of 0.02μM, and a high sensitivity of 267.2mA mol(-1)cm(-2), which is one of the highest values among the non-enzymatic sensors based on inorganic oxides. The Co9S8 sensor also exhibits good response toward glucose at different concentrations. These results demonstrate that the as-prepared Co9S8 hollow spheres have a potential application in the development of sensors for enzyme-free detection of H2O2 and glucose.

Synthesis of NiCo2O4/Nano-ZSM-5 nanocomposite material with enhanced electrochemical properties for the simultaneous determination of ascorbic acid, dopamine, uric acid and tryptophan

The high electrocatalytic activity of the sensor can be attributed to the highly dispersed NiCo₂O₄ on Nano-ZSM-5 matrix.