Nano-TiO2 modified carbon paste sensor for electrochemical nicotine detection using anionic surfactant

Electrodeposition of paracetamol oxide for intelligent portable ratiometric detection of nicotine and ethyl vanillin β-D-glucoside

Herein, the electrodeposition of paracetamol oxide (PA ox) for the intelligent portable ratiometric detection of nicotine (NIC) and ethyl vanillin β-D-glucoside (EVG) is reported. PA ox electrodeposited on a screen-printed carbon electrode (SPCE) was used as a new fixed state ratiometric reference probe. A portable electrochemical workstation combined with a smart phone was applied as an intelligent portable electrochemical sensing platform. The sensor was studied by scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FT-IR), ultraviolet-visible spectrophotometry (UV-vis), theoretical calculation, chronoamperometry, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). Under optimized conditions, the detection range of NIC is 10-200 μmol L-1, and the detection limit is 0.256 μmol L-1. The detection range of EVG was 10-180 μmol L-1, and the detection limit was 0.058 μmol L-1. The sensor can realize the real-time detection of NIC and EVG concentration in cigarette samples quickly and accurately, and has good anti-interference, repeatability and stability.

New Au/chitosan nanocomposite modified carbon paste sensor for voltammetric detection of nicotine

A profoundly touchy voltammetric sensor for detection of nicotine (NIC) in urine and tobacco specimens has been developed in light of the boosted electrochemical response of NIC at gold and chitosan nanocomposite modified carbon paste electrode (ACMCPE). Material characterization techniques Scanning Electron Microscope and Energy Dispersive X-ray (SEM & EDX) were utilized to describe the ACMCPE surface material. The impedance spectroscopy technique (EIS), cyclic voltammetry (CV), chronoamperometry (CA), and differential pulse voltammetry (DPV) were employed to explore the electrochemical sensing of NIC at ACMCPE. The created sensor exhibits an exceptional electrochemical sensitivity to NIC in a universal Britton-Robinson (B-R) buffer solution with a pH range of 2.0 to 8.0. The sensor shows a linear response over NIC concentration ranges of 4.0-320.0 µM, with the detection limit (LOD) of 7.6 µM. The prepared sensor has been shown to be exceptionally viable in detecting NIC with amazing selectivity and reproducibility. We suggest it as a trustworthy and useful electrochemical sensor for NIC location.

Development of Electrochemical Sensor Using Iron (III) Phthalocyanine/Gold Nanoparticle/Graphene Hybrid Film for Highly Selective Determination of Nicotine in Human Salivary Samples

Nicotine is the one of the major addictive substances; the overdose of nicotine (NIC) consumption causes increasing heart rate, blood pressure, stroke, lung cancer, and respiratory illnesses. In this study, we have developed a precise and sensitive electrochemical sensor for nicotine detection in saliva samples. It was built on a glassy carbon electrode (GCE) modified with graphene (Gr), iron (III) phthalocyanine-4,4',4″,4'''-tetrasulfonic acid (Fe(III)Pc), and gold nanoparticles (AuNPs/Fe(III)Pc/Gr/GCE). The AuNPs/Fe(III)Pc/Gr nanocomposite was prepared and characterized by using FE-SEM, EDX, and E-mapping techniques to confirm the composite formation as well as the even distribution of elements. Furthermore, the newly prepared AuNPs/Fe(III)Pc/Gr/GCE-nanocomposite-based sensor was used to detect the nicotine in phosphate-buffered solution (0.1 M PBS, pH 7.4). The AuNPs/Fe(III)Pc/Gr/GCE-based sensor offered a linear response against NIC from 0.5 to 27 µM with a limit of detection (LOD) of 17 nM using the amperometry (i-t curve) technique. This electrochemical sensor demonstrated astounding selectivity and sensitivity during NIC detection in the presence of common interfering molecules in 0.1 M PBS. Moreover, the effect of pH on NIC electro-oxidation was studied, which indicated that PBS with pH 7.4 was the best medium for NIC determination. Finally, the AuNPs/Fe(III)Pc/Gr/GCE sensor was used to accurately determine NIC concentration in human saliva samples, and the recovery percentages were also calculated.

Palladium Hydroxide (Pearlman's Catalyst) Doped MXene (Ti3C2Tx) Composite Modified Electrode for Selective Detection of Nicotine in Human Sweat

High concentrations of nicotine (40 to 60 mg) are more dangerous for adults who weigh about 70 kg. Herein, we developed an electrochemical transducer using an MXene (Ti₃C₂Tx)/palladium hydroxide-supported carbon (Pearlman's catalyst) composite (MXene/Pd(OH)₂/C) for the identification of nicotine levels in human sweat. Firstly, the MXene was doped with Pd(OH)₂/C (PHC) by mechanical grinding followed by an ultrasonication process to obtain the MXene/PHC composite. Secondly, XRD, Raman, FE-SEM, EDS and E-mapping analysis were utilized to confirm the successful formation of MXene/PHC composite. Using MXene/PHC composite dispersion, an MXene/PHC composite-modified glassy carbon electrode (MXene/PHC/GCE) was prepared, which showed high sensitivity as well as selectivity towards nicotine (300 µM NIC) oxidation in 0.1 M phosphate buffer (pH = 7.4) by cyclic voltammetry (CV) and amperometry. The MXene/PHC/GCE had reduced the over potential of nicotine oxidation (about 200 mV) and also enhanced the oxidation peak current (8.9 µA) compared to bare/GCE (2.1 µA) and MXene/GCE (5.5 µA). Moreover, the optimized experimental condition was used for the quantification of NIC from 0.25 µM to 37.5 µM. The limit of detection (LOD) and sensitivity were 27 nM and 0.286 µA µM^-1 cm², respectively. The MXene/PHC/GCE was also tested in the presence of Na⁺, Mg²⁺, Ca²⁺, hydrogen peroxide, acetic acid, ascorbic acid, dopamine and glucose. These molecules were not interfered during NIC analysis, which indicated the good selectivity of the MXene/PHC/GCE sensor. In addition, electrochemical determination of NIC was successfully carried out in the human sweat samples collected from a tobacco smoker. The recovery percentage of NIC in the sweat sample was 97%. Finally, we concluded that the MXene/PHC composite-based sensor can be prepared for the accurate determination of NIC with high sensitivity, selectivity and stability in human sweat samples.

Nicotine in Complex Samples: Recent Updates on the Pretreatment and Analysis Method

Nicotine is a significant evaluation index of tobacco and its related products' quality, but nicotine overdose can pose serious health hazards and cause addiction and dependence, thus it can be seen that it is necessary to find suitable and efficient detection methods to precisely detect nicotine in diverse samples and complex matrices. In this review, an updated summary of the latest trends in pretreatment and analytical techniques for nicotine is provided. We reviewed various sample pretreatment methods, such as solid phase extraction, solid phase microextraction, liquid phase microextraction, QuEChERS, etc., and diverse nicotine assay methods including liquid chromatography, gas chromatography, electrochemical sensors, etc., focusing on the developments since 2015. Furthermore, the recent progress in the applications and applicability of these techniques as well as our prospects for future developments are discussed.HighlightsUpdated pretreatment and analysis methods of nicotine were systematically summarized.Microextraction and automation were main development trends of nicotine pretreatment.The introduction of novel materials added luster to nicotine pretreatment.The evolutions of ion source and mass analyzer were emphasized.

An electrochemical sensor for voltammetric detection of ciprofloxacin using a glassy carbon electrode modified with activated carbon, gold nanoparticles and supramolecular solvent

A highly sensitive and novel electrochemical sensor for ciprofloxacin (CIP) has been developed using gold nanoparticles deposited with waste coffee ground activated carbon on glassy carbon electrode (AuNPs/AC/GCE) and combined with supramolecular solvent (SUPRAS). The fabricated AuNPs/AC/GCE displayed good electrocatalytic activity for AuNPs. The addition of SUPRAS, prepared from cationic surfactants namely didodecyldimethylammonium bromide (DDAB) and dodecyltrimethylammonium bromide (DTAB), increased the electrochemical response of AuNPs. The detection of CIP was based on the decrease of the cathodic current of AuNPs. The electrochemical behavior of the modified electrode was investigated using cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. Under optimum conditions, the calibration plot of CIP exhibited a linear response in the range 0.5-25 nM with a detection limit of 0.20 nM. The fabricated electrochemical sensor was successfully applied to determine CIP in milk samples with achieved recoveries of 78.6-110.2% and relative standard deviations of <8.4%. The developed method was also applied to the analysis of pharmaceutical formulation and the results were compared with high-performance liquid chromatography.Graphical abstract.

Electrochemical Determination of Nicotine in Tobacco Products Based on Biosynthesized Gold Nanoparticles

In this work, gold nanoparticles were biosynthesized via Plectranthus amboinicus leaf extract as the reducing agent. A series of techniques were used for sample analysis. The biosynthesized gold nanoparticles (bAuNPs) are a uniform size with a spherical shape. The FTIR analysis reveals the presence of many oxygen-containing functional groups on the bAuNP surface. The cyclic voltammetry and electrochemical impedance spectroscopic characterizations reveal that while the bAuNPs have a slightly lower conductivity than chemically synthesized AuNPs (cAuNPs). However, the bAuNPs have a superior electrocatalytic performance toward nicotine reduction. After optimization, the bAuNP-modified SPE could detect nicotine linearly from 10 to 2,000 μM with a low detection limit of 2.33 μM. In addition, the bAuNPs/SPE have been successfully used for nicotine-containing-product analysis.

A Simple but Efficient Voltammetric Sensor for Simultaneous Detection of Tartrazine and Ponceau 4R Based on TiO2/Electro-Reduced Graphene Oxide Nanocomposite

In this work, we report a simple but efficient voltammetric sensor for simultaneous detection of ponceau 4R and tartrazine based on TiO2/electro-reduced graphene oxide nanocomposites (TiO2/ErGO). TiO2/ErGO nanocomposites were prepared by ultrasonically dispersing TiO2 nanoparticles (TiO2 NPs) into graphene oxide (GO) solution followed by a green in-situ electrochemical reduction. TiO2 NPs were uniformly supported on ErGO nanoflakes, which provides a favorable interface for the adsorption and subsequent oxidation of target analytes. TiO2/ErGO showed remarkable electrocatalytic capacity for the oxidation of ponceau 4R and tartrazine, with minimized oxidation overpotentials and boosted adsorptive striping differential pulse voltammetric (AdSDPV) response peak currents. Under the optimal experimental conditions, the anodic peak currents of ponceau 4R and tartrazine increase linearly with the respective natural logarithm of concentrations from 0.01 to 5.0 μM. The detection limits (LOD = 3σ/s) for ponceau 4R and tartrazine are 4.0 and 6.0 nM, respectively. The extraordinary analytical properties of TiO2/ErGO/GCE are primarily attributed to the synergistic enhancement effect from ErGO nanoflakes and TiO2 NPs. Moreover, the proposed TiO2/ErGO/GCE achieves reliable determination of ponceau 4R and tartrazine in orange juice with excellent selectively, reproducibility and stability. Together with simplicity, rapidness, and low cost, the proposed sensor demonstrates great potential for on-site detection of azo colorants.

Mechanistic Insight into a Novel Ultrasensitive Nicotine Assay Base on High-Efficiency Quenching of Gold Nanocluster Cathodic Electrochemiluminescence

Monitoring nicotine concentrations in human fluids is extremely crucial owing to the harmful effect of nicotine on human health. Herein, it is shown that nicotine could quench the cathodic electrochemiluminescence (ECL) of gold nanoclusters (AuNCs) with high efficiency. The ECL quenching mechanism of nicotine was studied in detail using various experimental tools and theoretical calculations. It was concluded that the strongly oxidizing intermediate SO₄^•-, produced from K₂S₂O₈, could oxidized nicotine, resulting in ECL emission quenching. On the basis of this high-efficiency ECL quenching of the AuNCs/K₂S₂O₈ system, a recyclable, ultrasensitive, and selective ECL sensing platform for nicotine detection was proposed. Even in the absence of any complex signal amplification techniques, the ECL sensor for nicotine detection showed an unprecedentedly low detection limit of 7.0 × 10^-13 M (S/N = 3) and a wide linear range over 8 orders of magnitude. Most remarkably, it could be successfully used for nicotine detection in human urine samples. This is expected to promote the investigations and applications on nicotine-related diseases. We believe that the proposed ECL platform can hold great prospects for commercialization in biomedical fields and tobacco industries.

Grafting homogenous electrochemical biosensing strategy based on reverse proximity ligation and Exo III assisted target circulation for multiplexed communicable disease DNA assay

Rapid and effective diagnosis of communicable disease is one of the critical issues of the modern society, especially for detecting different targets at the same time. In this work, a grafting homogenous electrochemical biosensing strategy is proposed by integrating of reverse proximity ligation and exonuclease III (Exo III) assisted target circulation to analyze hepatitis B (HBV) and human immunodeficiency (HIV). Specially, a two-wing nanodevice (TWD) with two detection paths is elaborately designed based on analogous proximity ligation assay. The reverse proximity ligation process provides a new way of signal conversion and amplification, what accomplished by demolishing the TWD in the presence of targets. Meanwhile, a vast number of signal probes are released via Exo III assisted target circulation. Then the signal probes are grafted on the universal sensing interface, which is decorated with graftable tetrahedron DNA (GTD). These lead to a highly amplified electrochemical signal. Compared with the conventional strategies, the grafting homogenous electrochemical biosensing strategy not only achieves convenient sensitive detection of multiple communicable diseases DNA simultaneously, but also performs well in the detection of sole target. This strategy effectively decreases the background, homogenizes the distribution of probes, and avoids the complex and time-consuming modification process of the working electrode, which holds great potential application in early diagnosis for communicable disease in the future.

Simple and rapid nicotine analysis using a disposable silica nanochannel-assisted electrochemiluminescence sensor

Nicotine analysis is essential to medicine, toxicology and the tobacco industry. However, no simple, portable and disposable method was developed to meet their demands. Here, we report a simple, rapid and disposable silica nanochannel (SAN)-based electrochemiluminescence (ECL) sensor for nicotine analysis by simply assembling a SAN electrode with a paper cover. The sensing principle of the disposable sensor is based on the size exclusion effect and charge selectivity, which obviously prolong the sensor service time. We find that the sensor exhibits good specificity to nicotine, and most of the complex matrices are unlikely to impact the detection. The performance of the disposable sensor in cigarettes, e-cigarettes, nicotine gums, and lozenges is fully validated, showing satisfactory linearity, sensitivity (a limit of detection of 27.82 nM), and accuracy (a recovery between 96.00% and 106.51%). The disposable sensor can be potentially applied for on-site nicotine analysis.

Plasmophore Enhancement in Fibroblast Green Fluorescent Protein-Positive Cells Excited by Smoke

Considering the large consumption of nicotine and its sedative/stimulant effect on different organs of the body, the detection of low concentration of this material and its subsequent effect on live animals plays a significant role. Optical detection techniques such as plasmonics are the pioneers in highly sensitive detection techniques. However, for investigating the nicotine/smoke effect on live cells, not only the interaction between cell nicotine should be optimized but also the plasmonic interface should show a high sensitivity to the reception of nicotine by the cell receptors. In this study, the sensitivity of the plasmonic detection system was greatly increased using the coupling of plasmon and fluorophore. This coupling could enhance the main plasmonic signal several orders of magnitude besides improving Δ and Ψ ellipsometry parameters. Benefiting from the green fluorescence proteins, the phase shift and the amplitude ratio between the reflections under s- and p-polarized light enhance considerably which verifies the coupling of the dipole of the fluorescence emitter and the plasmons of the metal nanostructure. For 1 s increase of the maintenance time, we encountered a considerable increase in the Δ values that were 0.15° for T _e = 1 s and 0.24° for T _e = 3 s. Benefiting from extracted ellipsometry parameters, this study could open new avenues toward studying the effect of various types of drugs and stimulants on biological samples using a novel plasmophore platform.

Developments and applications of nanomaterial-based carbon paste electrodes

This review summarizes the progress that has been made in the past ten years in the field of electrochemical sensing using nanomaterial-based carbon paste electrodes. Following an introduction into the field, a first large section covers sensors for biological species and pharmaceutical compounds (with subsections on sensors for antioxidants, catecholamines and amino acids). The next section covers sensors for environmental pollutants (with subsections on sensors for pesticides and heavy metal ions). Several tables are presented that give an overview on the wealth of methods (differential pulse voltammetry, square wave voltammetry, amperometry, etc.) and different nanomaterials available. A concluding section summarizes the status, addresses future challenges, and gives an outlook on potential trends.

Moxifloxacin Hydrochloride Electrochemical Detection at Gold Nanoparticles Modified Screen-Printed Electrode

It appeared that either the carbon paste or the screen-printed carbon electrodes that were modified with gold nanoparticles (AuNPs) gave rise to the largest current responses after a rapid screening of various nanomaterials as modifiers of carbon composite electrodes in view of designing an electrochemical sensor for Moxifloxacin Hydrochloride (Moxi). The screen-printed electrode (SPE) support was preferred over the carbon paste one for its ability to be used as disposable single-use sensor enabling the circumvention of the problems of surface fouling encountered in the determination of Moxi. The response of AuNPs modified SPE to Moxi was investigated by cyclic voltammetry (CV) (including the effect of the potential scan rate and the pH of the medium), chronoamperometry, and differential pulse voltammetry (DPV) after morphological and physico-chemical characterization. DPV was finally applied to Moxi detection in phosphate buffer at pH 7, giving rise to an accessible concentration window ranging between 8 µM and 0.48 mM, and the detection and quantification limits were established to be 11.6 µM and 38.6 µM, correspondingly. In order to estimate the applicability of Moxi identification scheme in actual trials, it was practiced in a human baby urine sample with excellent recoveries between 99.8 % and 101.6 % and RSDs of 1.1-3.4%, without noticeable interference.

Titania/Electro-Reduced Graphene Oxide Nanohybrid as an Efficient Electrochemical Sensor for the Determination of Allura Red

Titania/electro-reduced graphene oxide nanohybrids (TiO2/ErGO) were synthesized by the hydrolysis of titanium sulfate in graphene oxide suspension and in situ electrochemical reduction. It provides a facile and efficient method to obtain nanohybrids with TiO2 nanoparticles (TiO2 NPs) uniformly coated by graphene nanoflakes. TiO2/ErGO nanohybrids were characterized by transmission electron microscopy, X-ray diffraction, cyclic voltammogram, and electrochemical impedance spectroscopy in detail. Compared with pure ErGO and TiO2 NPs, TiO2/ErGO nanohybrids greatly enhanced the electrocatalytic activity and voltammetric response of Allura Red. In the concentration range of 0.5-5.0 μM, the anodic peak currents of Allura Red were linearly correlated to their concentrations. However, the linear relationship was changed to the semi-logarithmic relationship at a higher concentration region (5.0-800 μM). The detection limit (LOD) was 0.05 μM at a signal-to-noise ratio of 3. The superior sensing performances of the proposed sensor can be ascribed to the synergistic effect between TiO2 NPs and ErGO, which provides a favorable microenvironment for the electrochemical oxidation of Allura Red. The proposed TiO2/ErGO/GCE showed good reproducibility and stability both in determination and in storage, and it can accurately detect the concentration of Allura Red in milk drinks, providing an efficient platform for the sensitive determination of Allura Red with high reliability, simplicity, and rapidness.

Dye-Modified Metal-Organic Framework as a Recyclable Luminescent Sensor for Nicotine Determination in Urine Solution and Living Cell

A water-stable and pH-independent sensor for qualitative and quantitative detection of nicotine in urine solution and living cell was successfully developed. This material, named MB@UiO-66-NH₂, can be synthesized by encapsulating methylene blue (MB) with a well-known metal-organic framework (MOF) UiO-66-NH₂ through a simple impregnation method. The fluorescence intensity of the system was significantly enhanced when a certain amount of nicotine was added. In the meanwhile, MB is reduced by reductive nicotine to form leucomethylene blue (LB). The proposed sensor displayed excellent selectivity and sensitivity toward nicotine with limit of detection (LOD) of 0.98 μM, which is comparable or even better than that of the electrochemistry detecting methods for nicotine. The obvious enhancement and blue shift of the emission arise from the photoinduced electron transfer (PET) from LB to the UiO-66-NH₂. The photophysical properties and the sensing applications of MB@UiO-66-NH₂ suggest that this composite can be acted as a sensitive, selective, recyclable, and fluorogenic sensor for nicotine determination in urine solution and living cell.

Nicotinamide adenine dinucleotide immobilized tungsten trioxide nanoparticles for simultaneous sensing of norepinephrine, melatonin and nicotine

Herein, we report the anionic surfactant, ethylene diamine tetraacetic acid (EDTA), mediated synthesis of WO₃ nanoparticles and its subsequent modification through gamma irradiation (GI) and electrochemical immobilization with nicotinamide adenine dinucleotide (NAD). Glassy carbon electrode (GCE) modified with GI-WO₃ NPs and the enzyme NAD exhibited strong electro-oxidation of three important biomolecules such as norepinephrine (NEP), melatonin (MEL) and nicotine (NIC) in 0.1 M phosphate buffer saline (PBS) at physiological pH of 7. Square wave voltammetry (SWV) studies exhibited three well-defined peaks at potentials of 120, 570 and 840 mV, corresponding to the oxidation of NEP, MEL and NIC respectively, indicating that simultaneous determination of these compounds is feasible at the NAD/GI EDTA-WO₃/GCE. The proposed sensor displayed a wide linear range of 0.010-1000 μM with the lowest detection limit of 1.4 nM for NEP, 2.6 nM for MEL and 1.7 nM for NIC respectively. Furthermore, the modified electrode was successfully applied to detect NEP, MEL and NIC in pharmaceutical and cigarette samples with excellent selectivity and reproducibility.

Real-time fish stress visualization came true：A novel multi-stage color-switching wireless biosensor system

An optical communication type biosensor system has been developed which can measure blood glucose concentration, which is a stress indicator of fish, in real-time while fish swimming freely. However, this system is hard to make instant acknowledgment of fish stress level which has to contain an unavoidable delay in the judgment. In this research, we aimed to develop a novel stress visualization system which can quickly judge the levels for fish stress response instantly based on a color changeable LED while another LED was designed to send data. The present system is based on the principle of converting the output current value measured by the glucose biosensor corresponding to the stress response into a voltage value. Then, the color and stress switching points of the LED (Red, Yellow, Green) were decided based on the voltage value gained from the biosensor which mentioned above. Furthermore, we attempted to use our biosensor system to make real-time monitoring of fish stress in vivo. As results, the proposed sensor can make real-time measurement of glucose and shows a great response to those of actual fish sample in the range from 35.36 to 300 mg dl^-1 (R = 0.9899). When the glucose concentration in the collected sample was switched to the concentration pre-sett, it was successful to switch the LED color according to the gained voltage value both in vitro and in vivo. Furthermore, when monitoring the stress responses of the fish in vivo, color switching corresponding to the sensor output current value was observed successfully.

DNA conformational polymorphism for biosensing applications

In this mini review, we will briefly introduce the rapid development of DNA conformational polymorphism in biosensing field, including canonical DNA duplex, triplex, quadruplex, DNA origami, as well as more functionalized DNAs (aptamer, DNAzyme etc.). Various DNA structures are adopted to play important roles in sensor construction, through working as recognition receptor, signal reporter or linking staple for signal motifs, etc. We will mainly summarize their recent developments in DNA-based electrochemical and fluorescent sensors. For the electrochemical sensors, several types will be included, e.g. the amperometric, electrochemical impedance, electrochemiluminescence, as well as field-effect transistor sensors. For the fluorescent sensors, DNA is usually modified with fluorescent molecules or novel nanomaterials as report probes, excepting its core recognition function. Finally, general conclusion and future perspectives will be discussed for further developments.

Simultaneous determination of ascorbic acid, dopamine and uric acid by a novel electrochemical sensor based on N2/Ar RF plasma assisted graphene nanosheets/graphene nanoribbons

A novel nitrogen/argon (N₂/Ar) radio frequency (RF) plasma functionalized graphene nanosheet/graphene nanoribbon (GS/GNR) hybrid material (N₂/Ar/GS/GNR) was developed for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Various nitrogen mites introduced into GS/GNR hybrid structure was evidenced by a detailed microscopic, spectroscopic and surface area analysis. Owing to the unique structure and properties originating from the enhanced surface area, nitrogen functional groups and defects introduced on both the basal and edges, N₂/Ar/GS/GNR/GCE showed high electrocatalytic activity for the electrochemical oxidations of AA, DA, and UA with the respective lowest detection limits of 5.3, 2.5 and 5.7 nM and peak-to-peak separation potential (ΔE_P) (vs Ag/AgCl) in DPV of 220, 152 and 372 mV for AA/DA, DA/UA and AA/UA respectively. Moreover, the selectivity, stability, repeatability and excellent performance in real time application of the fabricated N₂/Ar/GS/GNR/GCE electrode suggests that it can be considered as a potential electrode material for simultaneous detection of AA, DA, and UA.

Synthesis of a simply modified electrochemical nicotine sensor based on silver nanoparticles

An innovative electrochemical nicotine modified sensor was created by chemically mixing a carbon paste with silver nano powder to prepare an Ag nanoparticle modified carbon paste electrode. Different electrochemical techniques including cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy in both aqueous and micellar media were used. The surface morphology was also detected using scanning electron microscope and energy dispersive X-ray analysis techniques. Nicotine measurements were investigated in Britton–Robinson buffer solutions with a pH range of 2.0–8.0 containing 1.0 mmol/L sodium dodecyl sulfate. The electrode-based NIC sensor exhibited a high sensitivity in quantitative analysis, and its detection limit could be as low as 0.0036 μmol/L with linearity ranging from 0.8 μmol/L to 800 μmol/L. In addition, due to its good reproducibility, anti-interference performance, and long-term stability, the proposed sensor is capable of detecting trace levels of nicotine in urine samples and different brands of commercial cigarettes.

Non-light-driven reduced graphene oxide anchored TiO2 nanocatalysts with enhanced catalytic oxidation performance

As a single-atom-thick carbon material with high surface and good conductivity, graphene provides an ideal platform for designing composite nanomaterials for high-performance catalytic system. Herein, we obtained a TiO₂-reduced graphene oxide nanocomposite (TiO₂-RGO) with graphene oxide and tetrabutyl titanate using a facile in situ hydrothermal method. The merit of this method is that the nanocomposites could be produced directly from graphene oxide in the hydrothermal reaction, where the reduction of graphene oxide and the decoration of TiO₂ occurred simultaneously. TiO₂ nanoparticles anchored on graphene sheets as spacers to keep the neighboring sheets separated. The in situ growth route provides a desirable platform for constructing graphene-supported nanocomposites with improved properties. As one of the major applications of the nanocomposites, we investigate the performance of as-prepared TiO₂-RGO as effective non-light-driven catalysts for activating H₂O₂ in oxidative degradation of the dye. The system was employed in oxidation degradation not only to reach high degradation efficiency but also to avoid any energy consumption. Meanwhile, the proposed catalytic system processes broad-spectrum oxidative degradation activity for different model organic pollutants. Overall, this work could provide new insights into the fabrication of a TiO₂-RGO as high performance catalysts and facilitate their application in the environmental protection issues.

The application of a bee glue-modified sensor in daclatasvir dual effect detection

A simple and novel carbon paste sensor containing chemically mixed propolis (bee glue) and graphene oxide (GO) was prepared, then electrochemical deposition of silver nanoparticles (AgNPs) was performed to fabricate a selective and sensible electrochemical sensor to detect Daclatasvir (DAC).

Electrodeposition of Au nanoparticles on poly(diallyldimethylammonium chloride) functionalized reduced graphene oxide sheets for voltammetric determination of nicotine in tobacco products and anti-smoking pharmaceuticals

The principal objective of this study was to develop a sensitive and selective electrochemical sensor for nicotine detection based on a novel PDDA-RGO/Au nanocomposite.