Smartphone-Integrated Automated Sensor Employing Electrochemically Engineered 3D Bimetallic Nanoflowers for Hydrogen Peroxide Quantification in Milk

Hydrogen peroxide (H2O2), one of the reactive oxygen species in living beings, serves as a regulator of various cellular processes. However, excessive peroxide concentrations are linked to oxidative stress and promptly disrupt cellular components, leading to several pathological conditions in the body. Moreover, it is extremely reactive and has a limited lifetime; thus, H2O2 sensing remains a prominent focus of research. Enzymatic sensing probes were widely employed to detect H2O2 in the recent past; however, they are susceptible to intrinsic chemical and thermal instabilities, which decrease the reliability and durability of the surface. This research was designed to come up with a feasible solution to this problem. Herein, a novel nonenzymatic peroxidase-mimic three-dimensional (3D) bimetallic nanoflower has been synergistically engineered for quick sensing of H2O2. The sensor platform showed minimal resistance or enhanced charge transfer properties as well as remarkable analytical capability, having a broad linear range between 0.01 and 1 nM and a detection limit of 1.46 ± 0.07 pM. The probe responded to changes in H2O2 concentration in just 2.10 ± 0.02 s, making it a quick sensing platform for H2O2 tracking. This peroxidase-mimic nanozyme probe showed minimal sensitivity to interferants often seen in real-world sample matrices and possessed good recoveries ranging from 92.88 to 99.09% in milk samples. Further, a facile and user-friendly smartphone application (APP) named "HPeroxide-Check" was developed and integrated into the sensor to check the milk adulteration by detecting H2O2. It processes the current output obtained from the sensing interface and provides real-time peroxide concentrations in milk. The entire procedure of fabricating the probe is a single, highly robust step that takes only 10 min and is coupled with a smartphone APP, highlighting the sensor's quick manufacturing and deployment for automated H2O2 monitoring in industrial and point-of-care settings.

Flexible and disposable gold nanoparticles-N-doped carbon-modified electrochemical sensor for simultaneous detection of dopamine and uric acid

Catalytic and electrocatalytic applications of supported metal nanoparticles are hindered due to an aggregation of metal nanoparticles and catalytic leaching under harsh operations. Hence, stable and leaching free catalysts with high surface area are extremely desirable but also challenging. Here we report a gold nanoparticles-hosted mesoporous nitrogen doped carbon matrix, which is prepared using bovine serum albumin (BSA) through calcination. BSA plays three roles in this process as a reducing agent, capping agent and carbon precursor, hence the protocol exhibits economic and sustainable. Gold nanoparticles at N-doped BSA carbon (AuNPs@NBSAC)-modified three-electrode strip-based flexible sensor system has been developed, which displayed effective, sensitive and selective for simultaneous detection of uric acid (UA) and dopamine (DA). The AuNPs@NBSAC-modified sensor showed an excellent response toward DA with a linear response throughout the concentration range from 1 to 50 μM and a detection limit of 0.05 μM. It also exhibited an excellent response toward UA, with a wide detection range from 5 to 200 μM as well as a detection limit of 0.1 μM. The findings suggest that the AuNPs@NBSAC nanohybrid reveals promising applications and can be considered as potential electrode materials for development of electrochemical biosensors.

Phase-transfer-assisted synthesis of cysteine-Ag nanoparticles/graphene oxide nanocomposite and its enhanced performance in antibiosis and biosensing

We report a facile, rapid, phase-transfer-assisted process to prepare Ag nanoparticles (AgNP) loaded graphene oxide (GO) nanocomposite, by using cysteine as a highly-effective phase transfer agent for AgNP movement from organic phase to water and subsequently as a covalent linkage for immobilizing AgNP on GO. The obtained c-Ag/GO nanocomposite possesses high nanoparticle loading efficiency, small particle size and monodispersity, strong binding force and good water dispersibility, which endow it with great potential in a variety of bio-applications. To illustrate potentail application, c-Ag/GO and its derivatives c-Ag/rGO were used for antibiosis and biosensing, respectively. The c-Ag/GO composite demonstrates high antibacterial activity against E. coli with a minimal bactericidal concentration of 10 μg ml^-1. The biosensor based on c-Ag/rGO exhibits rapid and sensitive response for uric acid detection with a detection limit of 0.025 μM, a sensitivity of 5.76 μA mM^-1 and a wide linear range of 0.025 ∼ 2250 μM. The comparative analysis with relevant nanocomposites also reveals the precedence of c-Ag/GO in these applications, thus highlighting the advantages of the developed preparation method for c-Ag/GO.

Hierarchical defective palladium-silver alloy nanosheets for ethanol electrooxidation

Tuning the chemical composition and surface structure of electrodes is demonstrated as a feasible and effective strategy to tailor advanced catalysts for energy electrocatalysis. In this work, hierarchical palladium-silver alloy nanosheets (PdAg NS) with the thickness ~7 atoms and rich atomic defects are successfully prepared, using the carbon monoxide (CO) confinement approach. The optimized Pd₇Ag₃ NS/C exhibits 8.8 times higher catalytic peak current density and much better stability toward ethanol electrooxidation than Pd NS/C catalyst. The catalytic enhancement mechanism could be attributed to the synergetic effects among optimized electronic structure of Pd, novel architecture, and rich atomic defects.

A modified hybrid silsesquioxane/histidine composite for copper and zinc adsorption and it behavior in the electro-oxidation of ascorbic acid

Octa-(3-chloropropryl)silsesquioxane was chemically modified with histidine (SSQ-H) and characterized by spectroscopy in the infrared region (FT-IR), X-ray diffraction (XRD), X-ray Dispersive Energy Spectroscopy (EDX), Scanning Electron Microscopy (SEM). The analytical properties of SSQ-H were tested regarding of Cu²⁺ and Zn²⁺ adsorption and as an electrochemical sensor for the detection of ascorbic acid. The metal sorption results indicate that maximum amount of Cu²⁺ and Zn²⁺ adsorbed (Nf_max) were 1.58 × 10^-3 and 5.67 × 10^-4 mol g^-1, respectively. After Cu²⁺ and Zn²⁺ ion adsorption and interaction with potassium hexacyanoferrate (III), the investigated materials displayed electroactivity for ascorbic acid detection. The anodic peak currents responses of a graphite paste electrode containing CuHCFSSQ-H presented a linear response in the concentration range of 4.0 × 10^-4 to 4.0 × 10^-3 mol L^-1 for ascorbic acid detection. The limit of detection was of 2.99 × 10^-4 mol L^-1, with an amperometric sensitivity of 1.69 μA/mol L^-1. The intensity of the anodic peak currents of the graphite paste electrode containing ZnHCFSSQ-H in the concentration range of 9.0 × 10^-5 to 9.0 × 10^-4 mol L^-1 also displayed a linear response. The limit of detection was of 6.76 × 10^-5 mol L^-1, with an amperometric sensitivity of 0.0206 A/mol L^-1.

Copper-induced synthesis of palladium/copper popcorn nanoparticles as sensors for differential pulse voltammetric determination of dopamine

Popcorn nanoparticles (pop-NPs) consisting of a Pd/Cu alloy were synthesized using a seed-mediated growth method. The Cu and Pd atoms were co-deposited on a cubic Pd seed to reduce the energy of fault stacking. The same synthesis method with a reduced volume of the Cu(II) salt leads to Pd/Cu alloy nanoparticles with branches (br-NPs). Large Pd nanocubes (Pd NCs) were prepared via epitaxial deposition and using tetrachloropalladate (PdCl₄^2-) only. The high-resolution TEM analysis results show the pop-NPs and br-NPs to be single crystals with [Formula: see text] and [Formula: see text] planes, respectively. The results of X-ray photoelectron spectroscopy and cyclic voltammetry measurements corroborated that Pd is enriched on both surfaces. The materials were placed on a glassy carbon electrode to obtain a differential pulse voltammetric sensor for dopamine (DA). The electrochemical sensitivities are (a) 1.55 μA μM^-1 cm^-2 for the Pd/Cu pop-NP sensor in its linear range (15-300 μM), (b) 1.17 μA μM^-1 cm^-2 for the br-NP sensor in the linear range (15-200 μM), and (c) 0.97 μA μM^-1 cm^-2 for the Pd NC sensor in its linear range (15-100 μM). The best working potentials are near 0.10 V (vs. SCE) for all three sensors. The pop-NP-based sensor performs particularly well due to it selectivity over ascorbic and uric acid. Graphical abstract Pd/Cu popcorn nanoparticles (pop-NPs), nanoparticles with branches (br-NPs), and Pd nanocubes (NCs) were synthesized using seed-mediated growth methods and directly used on glassy carbon electrodes for non-enzymatic sensing of dopamine.

Biomass-derived Carbon Quantum Dots for Visible-Light-Induced Photocatalysis and Label-Free Detection of Fe(III) and Ascorbic acid

Visible-light-driven photocatalysts prepared using renewable resources are crucial but challenging to develop for the efficient degradation of organic pollutants, which is required to solve ever-increasing water deterioration issues. In this study, we report a visible-light-responsive photocatalyst for the efficient degradation of methylene blue (MB) as a model pollutant dye. Green-emissive carbon quantum dots (CQDs) were synthesized from pear juice via a facile, scalable, one-pot solvothermal process. The as-synthesized CQDs exhibit superior photocatalytic activity under visible-light irradiation owing to their efficient light absorption, electron transfer, and separation of photogenerated charge carriers, facilitating ~99.5% degradation of MB within 130 min. A possible mechanism for the photocatalysis is proposed on the basis of comprehensive active species trapping experiments. Furthermore, the CQDs were used in a specific sensitive assay for Fe(III) and ascorbic acid (AA), even with interference from other metal ions. The fluorescence emission of CQDs was "turned off" specifically upon binding of Fe(III) and "turned on" with AA. The prepared CQDs represent efficient photocatalysts and fluorescent probes that are not restricted by toxicity, cost, or lack of scalability.

Plasma-induced covalent immobilization and patterning of bioactive species in microfluidic devices

Here, we present a straightforward technique to create bio-functional microfluidic channels using CO2 plasma to induce both carboxylic and hydroxyl groups onto the channel surface. Consequently, not only does the surface allow for irreversible covalent bonding to an oxygen plasma treated PDMS for microfluidic device fabrication, but it also provides functionality for biomolecular immobilization. Furthermore, we demonstrate integration of this technique with microcontact printing to covalently micropattern functional biomolecules inside microfluidic channels. The bio-functionality and efficacy of the microcontact printed antibodies is demonstrated for both bioassays as well as patterning and culturing different cell lines. Results show that the introduced method can be an excellent candidate for cell culture studies in microfluidics. With the new printing method, full cell confluency (∼400 cells per mm2) was achieved after incubation for only 1 day, which is significantly greater than other conventional cell culture techniques inside microfluidic devices. As a proof of concept, we demonstrated the endothelial cells functionality by stimulating von Willebrand Factor secretion under shear stress. This is done via perfusion of histamine through the channel and performing immunofluorescence labeling to observe the inflammatory response of the cells. The developed method eliminates the need for wet chemistry and significantly simplifies producing bio-functional chips which can be used for biosensing, organs-on-chips and tissue engineering applications.

Ag and Au nanoparticles/reduced graphene oxide composite materials: Synthesis and application in diagnostics and therapeutics

The exceptional electrical, thermal, optical and mechanical properties have made two dimensional sp² hybridized graphene a material of choice in both academic as well as industrial research. In the last few years, researchers have devoted their efforts towards the development of graphene/polymer, graphene/metal nanoparticle and graphene/ceramic nanocomposites. These materials display excellent mechanical, electrical, thermal, catalytic, magnetic and optical properties which cannot be obtained separately from the individual components. Fascinating physical and chemical properties are displayed by noble metal nanomaterials and thus they represent model building blocks for modifying nanoscale structures for diverse applications extending from catalysis, optics to nanomedicine. Insertion of noble metal (Au, Ag) nanoparticles (NPs) into chemically derived graphene is thus of primary importance to open new avenues for both materials in various fields where the specific properties of each material act synergistically to provide hybrid materials with exceptional performances. This review attempts to summarize the different synthetic procedures for the preparation of Ag and Au NPs/reduced graphene oxide (rGO) composites. The synthesis processes of metal NPs/rGO composites are categorised into in-situ and ex-situ techniques. The in-situ approach consists of simultaneous reduction of metal salts and GO to obtain metal NPs/rGO nanocomposite materials, while in the ex-situ process, the metal NPs of desired size and shape are first synthesized and then transferred onto the GO or rGO matrix. The application of the Ag NPs and Au NPs/rGO composite materials in the area of biomedical (drug delivery and photothermal therapy) and biosensing are the focus of this review article.

Ultrafine Fe3C nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine

A pyrolytic method is described for preparation of ultrafine Fe₃C nanoparticles incorporated into N-doped graphitic carbon nanosheets (Fe₃C@NGCSs). Iron phthalocyanine and graphitic carbon nitride (g-C₃N₄) are used as starting materials. The hybrid nanocomposite was placed on a glassy carbon electrode (GCE) and then applied to simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and xanthine (XA). Figures of merits are as follows: for AA, the linear response range covers the 54.0-5491.0 μM range, the lower detection limit is 16.7 μM, and the best working voltage (vs. the saturated calomel electrode (SCE)) is 0.05 V. The respective data for DA are 1.2-120.8 μM, 0.34 μM and 0.19 V (vs. SCE). For UA, the respective data are 4.8-263.0 μM, 1.4 μM and 0.32 V (vs. SCE), and for XA the data are 4.8-361.0 μM, 1.5 μM and 0.71 V (vs. SCE). The method was successfully applied to their simultaneous determination in spiked serum samples. Graphical abstract Ultrafine Fe₃C nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine.

Facile Synthesis of MnO2 Nanoflowers/N-Doped Reduced Graphene Oxide Composite and Its Application for Simultaneous Determination of Dopamine and Uric Acid

This study reports facile synthesis of MnO2 nanoflowers/N-doped reduced graphene oxide (MnO2NFs/NrGO) composite and its application on the simultaneous determination of dopamine (DA) and uric acid (UA). The microstructures, morphologies, and electrochemical performances of MnO2NFs/NrGO were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), respectively. The electrochemical experiments showed that the MnO2NFs/NrGO composites have the largest effective electroactive area and lowest charge transfer resistance. MnO2NFs/NrGO nanocomposites displayed superior catalytic capacity toward the electro-oxidation of DA and UA due to the synergistic effect from MnO2NFs and NrGO. The anodic peak currents of DA and UA increase linearly with their concentrations varying from 0.2 μM to 6.0 μM. However, the anodic peak currents of DA and UA are highly correlated to the Napierian logarithm of their concentrations ranging from 6.0 μM to 100 μM. The detection limits are 0.036 μM and 0.029 μM for DA and UA, respectively. Furthermore, the DA and UA levels of human serum samples were accurately detected by the proposed sensor. Combining with prominent advantages such as facile preparation, good sensitivity, and high selectivity, the proposed MnO2NFs/NrGO nanocomposites have become the most promising candidates for the simultaneous determination of DA and UA from various actual samples.

Morphology-Dependent Electrochemical Sensing Properties of Iron Oxide-Graphene Oxide Nanohybrids for Dopamine and Uric Acid

Various morphologies of iron oxide nanoparticles (Fe2O3 NPs), including cubic, thorhombic and discal shapes were synthesized by a facile meta-ion mediated hydrothermal route. To further improve the electrochemical sensing properties, discal Fe2O3 NPs with the highest electrocatalytic activity were coupled with graphene oxide (GO) nanosheets. The surface morphology, microstructures and electrochemical properties of the obtained Fe2O3 NPs and Fe2O3/GO nanohybrids were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. As expected, the electrochemical performances were found to be highly related to morphology. The discal Fe2O3 NPs coupled with GO showed remarkable electrocatalytic activity toward the oxidation of dopamine (DA) and uric acid (UA), due to their excellent synergistic effect. The electrochemical responses of both DA and UA were linear to their concentrations in the ranges of 0.02-10 μM and 10-100 μM, with very low limits of detection (LOD) of 3.2 nM and 2.5 nM for DA and UA, respectively. Moreover, the d-Fe2O3/GO nanohybrids showed good selectivity and reproducibility. The proposed d-Fe2O3/GO/GCE realized the simultaneous detection of DA and UA in human serum and urine samples with satisfactory recoveries.

Low fouling electrochemical sensing in complex biological media by using the ionic liquid-doped conducting polymer PEDOT: application to voltammetric determination of dopamine

An electrochemical sensor that can resist biofouling even when operated in complex biological medium is developed for the determination of dopamine. It is based on the use of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) that is doped with the water insoluble ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. A glassy carbon electrode modified with PEDOT/IL is shown to enable accurate determination of dopamine, as a model analyte in the presence of high concentrations of proteins, and resist biological fouling even in native serum. It exhibited a low limit of detection of 33 nM for the detection of dopamine, with a wide linear range from 0.2 to 328 μM (at 0.2 V vs. saturated calomel electrode). The PEDOT/IL modified glassy carbon electrode has a porous microstructure, high electrical conductivity and good stability. The sensor can be used to quantify dopamine in human urine samples with satisfying accuracy. Graphical abstract An antifouling electrochemical sensor capable of detecting target in complex biological samples was developed based on the use of a conducting polymer (PEDOT) that was doped with a water insoluble ionic liquid.

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.

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters.

Nitrogen-doped fluorescent graphene nanosheets as visible-light-driven photocatalysts for dye degradation and selective sensing of ascorbic acid

Facile synthesis of water soluble fluorescent N-doped graphene nanosheets for multifunctional applications in photocatalysis and sensing.

Cu2+-BTC based metal–organic framework: a redox accessible and redox stable MOF for selective and sensitive electrochemical sensing of acetaminophen and dopamine

A Cu²⁺ plus benzenetricarboxylate (BTC) based ‘3D’ metal–organic framework HKUST-1 was synthesized via a facile microwave assisted route.

Exploring the potential of electroless and electroplated noble metal-semiconductor hybrids within bio- and environmental sensing

Over the last two decades, the rapid development and widespread application of nanomaterials has significantly influenced research in various fields, including analytical chemistry and biosensing technologies. In particular, the simple functionalization and tuning of noble metal nanoparticle (NP) surface chemistry resulted in the development of a series of novel biosensing platforms with quick read-out and enhanced capabilities towards specific analyte detection. Moreover, noble metal NPs possess a number of unique properties, viz. high surface-to-volume ratio and excellent spectral, optical, thermal, electrical and catalytic characteristics. This manuscript provides an elaborate review on galvanic noble metal NPs deposited onto semiconductor surfaces, from the preparation stage towards their application in biosensors and gas sensing. Two types of deposition approaches, viz. galvanic displacement/electroless and conventional electroplating, are introduced and compared. Furthermore, the analytical merit of hybrid nanomaterials towards the improvement of sensing abilities is highlighted. Finally, some limitations and challenges related to progress in the development and application of analytical devices based on electroless and electroplated noble metal NPs-semiconductor hybrids (NMNPsHs) in biochemical and environmental sensing are discussed.

Harnessing a previously unidentified capability of bacterial allosteric transcription factors for sensing diverse small molecules in vitro

A plethora of bacterial allosteric transcription factors (aTFs) have been identified to sense a variety of small molecules. Introduction of a novel aTF-based approach to sense diverse small molecules in vitro will signify a broad series of detection applications. Here, we found that aTFs could interact with their nicked DNA binding sites. Building from this new finding, we designed and implemented a novel aTF-based nicked DNA template-assisted signal transduction system (aTF-NAST) by using the competition between aTFs and T4 DNA ligase to bind to the nicked DNA. This aTF-NAST could reliably and modularly transduce the signal of small molecules recognized by aTFs to the ligated DNA signal, thus enabling the small molecules to be measured via various mature and robust DNA detection methods. Coupling this aTF-NAST with three DNA detection methods, we demonstrated nine novel biosensors for the detection of an antiseptic 4-hydroxybenzoic acid, a disease marker uric acid and an antibiotic tetracycline. These biosensors show impressive sensitivity and robustness in real-life analysis, highlighting the great potential of our aTF-NAST for biosensing applications.

Crystal-defect-induced facet-dependent electrocatalytic activity of 3D gold nanoflowers for the selective nanomolar detection of ascorbic acid

Understanding and exploring the decisive factors responsible for superlative catalytic efficiency is necessary to formulate active electrode materials for improved electrocatalysis and high-throughput sensing. This research demonstrates the ability of bud-shaped gold nanoflowers (AuNFs), intermediates in the bud-to-blossom gold nanoflower synthesis, to offer remarkable electrocatalytic efficiency in the oxidation of ascorbic acid (AA) at nanomolar concentrations. Multicomponent sensing in a single potential sweep is measured using differential pulse voltammetry while the kinetic parameters are estimated using electrochemical impedance spectroscopy. The outstanding catalytic activity of bud-structured AuNF [iAuNFp(Bud)/iGCp ≅ 100] compared with other bud-to-blossom intermediate nanostructures is explained by studying their structural transitions, charge distributions, crystalline patterns, and intrinsic irregularities/defects. Detailed microscopic analysis shows that density of crystal defects, such as edges, terraces, steps, ledges, kinks, and dislocation, plays a major role in producing the high catalytic efficiency. An associated ab initio simulation provides necessary support for the projected role of different crystal facets as selective catalytic sites. Density functional theory corroborates the appearance of inter- and intra-molecular hydrogen bonding within AA molecules to control the resultant fingerprint peak potentials at variable concentrations. Bud-structured AuNF facilitates AA detection at nanomolar levels in a multicomponent pathological sample.

Self-Cleaning Ceramic Tiles Produced via Stable Coating of TiO₂ Nanoparticles

The high photocatalytic power of TiO₂ nanoparticles has drawn great attention in environmental and medical applications. Coating surfaces with these particles enables us to benefit from self-cleaning properties and decomposition of pollutants. In this paper, two strategies have been introduced to coat ceramic tiles with TiO₂ nanoparticles, and the self-cleaning effect of the surfaces on degradation of an organic dye under ultraviolent (UV) exposure is investigated. In the first approach, a simple one-step heat treatment method is introduced for coating, and different parameters of the heat treatment process are examined. In the second method, TiO₂ nanoparticles are first aminosilanized using (3-Aminopropyl)triethoxysilane (APTES) treatment followed by their covalently attachment onto CO₂ plasma treated ceramic tiles via N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS) chemistry. We monitor TiO₂ nanoparticle sizes throughout the coating process using dynamic light scattering (DLS) and characterize developed surfaces using X-ray photoelectron spectroscopy (XPS). Moreover, hydrophilicity of the coated surfaces is quantified using a contact angle measurement. It is shown that applying a one-step heat treatment process with the optimum temperature of 200 °C for 5 h results in successful coating of nanoparticles and rapid degradation of dye in a short time. In the second strategy, the APTES treatment creates a stable covalent coating, while the photocatalytic capability of the particles is preserved. The results show that coated ceramic tiles are capable of fully degrading the added dyes under UV exposure in less than 24 h.

Pd–Ag decorated g-C3N4 as an efficient photocatalyst for hydrogen production from water under direct solar light irradiation

Pd–Ag bimetallic and monometallic nanoparticles were decorated on g-C₃N₄ and evaluated for their ability to produce H₂ through water splitting reactions.

Ultrafine Pt–Ni bimetallic nanoparticles anchored on reduced graphene oxide nanocomposites for boosting electrochemical detection of dopamine in biological samples

The present report demonstrates the development of a Pt–Ni/rGO composite electrochemical sensor for the detection of dopamine.

An ultra-sensitive electrochemical sensor for the detection of acetaminophen in the presence of etilefrine using bimetallic Pd–Ag/reduced graphene oxide nanocomposites

In this study we report a one-step procedure for the fabrication of Pd–Ag bimetallic nanoparticles on the surface of a graphene oxide (rGO) support.

CVD graphene as an electrochemical sensing platform for simultaneous detection of biomolecules

The development of electrochemical biosensors for the simultaneous detection of ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), and nitrite ([Formula: see text]) in human serum is reported in this work. Free-standing graphene nanosheets were fabricated on Ta wire using the chemical vapor deposition (CVD) method. CVD graphene, which here served as a sensing platform, provided a highly sensitive and selective option, with detection limits of AA, DA, UA, Trp, and [Formula: see text] of 1.58, 0.06, 0.09, 0.10, and 6.45 μM (S/N = 3), respectively. The high selectivity of the electrode is here explained by a relationship between the bandgap energy of analyte and the Fermi level of graphene. The high sensitivity in the oxidation current was determined by analyzing the influence of the high surface area and chemical structure of free-standing graphene nanosheets on analyte adsorption capacity. This finding strongly indicates that the CVD graphene electrode can be used as a biosensor to detect five analytes in human serum.

New Approach for Porous Chitosan-Graphene Matrix Preparation through Enhanced Amidation for Synergic Detection of Dopamine and Uric Acid

Amide-functionalized materials have emerged as promising nonprecious catalysts for electrochemical sensing and catalysis. The covalent immobilization of chitosan (CS) onto graphene sheet (GS) (denoted as CS-GS) has been done via higher degree of amidation reaction to develop an electrochemical sensing matrix for simultaneous determination of dopamine (DA) and uric acid (UA). The enhanced amidation between CS and GS has not been reported previously. However, electrochemical results have revealed that the CS-GS enhances the electrocatalytic performance in terms of the oxidation potential and peak current due to the higher degree of amide functionalization compared to that of CS/GS, which has a lower amidation. Differential pulse voltammetry-based studies have indicated that the CS-GS matrix works at a lower detection limit (0.14 and 0.17 μM) (S/N = 3) and over a longer linear range (1-700 and 1-800 μM), with a comparatively higher sensitivity (2.5 and 2.0 μA μM^-1 cm^-2), for DA and UA, respectively. In addition, the CS-GS matrix demonstrates good selectivity toward the detection of DA and UA in the presence of a 10-fold higher concentration of AA and glucose. The as-prepared three-dimensional porous CS-GS also endows selective determination toward DA and UA in various real samples.

Small biomolecule sensors based on an innovative MoS2–rGO heterostructure modified electrode platform: a binder-free approach

Hydrothermally synthesized MoS₂–rGO nanoflowers can simultaneously sense ascorbic acid (AA), dopamine (DA) and uric acid (UA) with good separating peak-to-peak potentials.

Dendritic unzipped carbon nanofibers enable uniform loading of surfactant-free Pd nanoparticles for the electroanalysis of small biomolecules

Illustration of the mechanisms of SCNF and preparation of Pd/GNF composites and Pd/GNF sensors for the simultaneous determination of small biomolecules.

Economical, facile synthesis of network-like carbon nanosheets and their use as an enhanced electrode material for sensitive detection of ascorbic acid

A highly sensitive electrochemical sensor for the detection of ascorbic acid (AA) was first fabricated using network-like carbon nanosheets (NCN) as an enhanced electrode modifier.