A frogspawn-like Ag@C core–shell structure for an ultrasensitive label-free electrochemical immunosensing of carcinoembryonic antigen in blood plasma

A three-dimensional (3D) frogspawn-like structure was achieved by simply coating nano-carbon outside silver nanospheres (Ag@C NFS) and used as a probe to capture the anti-carcinoembryonic antigen for the electrochemical immunosensing of carcinoembryonic antigen (CEA), a typical biomarker of several diseases such as gastric cancer, intestinal cancer and colon cancer. Moreover, Ag@C nanocables (Ag@C NCs) were aslo synthesized. By comparison, the globular 3D frogspawn-like structure endowed Ag@C NFS with a larger surface area, which is preferred to improve the capability of loading antibodies, higher water solubility, better biocompatibility and improved electrical conductivity, which was likely attributed to the synergistic effects of Ag and crystalline graphite carbon and the different structure with more hydroxyl groups exposed. Therefore, the resultant Ag@C NFS was used as an electrochemical immunosensing platform to fabricate a label-free immunosensor for the analysis of CEA, which showed an excellent immunosensing performance with a wide linear CEA detection range from 0.0001 ng mL⁻¹ to 100 ng mL⁻¹ and a low detection limit of 5.12 pg mL⁻¹. In particular, the good reproducibility, high stability and specificity of the proposed immunosensor ensured the successful application in the quantitative determination of CEA in cancerous human serum samples, providing a promising alternative to detect other biomarkers.

Novel frogspawn-like Ag@C nanoparticles were successfully used to fabricate an ultrasensitive electrochemical immunosensing platform toward CEA in human blood samples.     

Reagentless and sensitive determination of carcinoembryonic antigen based on a stable Prussian blue modified electrode

Reagentless and sensitive detection of tumor biomarkers using label-free electrochemical immunosensors is highly desirable for early and effective cancer diagnosis. Herein, we present a label-free electrochemical immunoassay platform based on surface-confined Prussian blue (PB) redox probes for sensitive and reagentless determination of carcinoembryonic antigen (CEA). To facilitate the electron transfer of probes and improve sensitivity, Au nanoparticles and PB (Au–PB) are electrochemically co-deposited on a carbon nanotube (CNT) modified glassy carbon electrode (GCE). A polydopamine (pDA) layer is coated on the Au–PB nanocomposite layer in situ as a bifunctional linker. In addition to improving the stability of PB, pDA also provides reducibility for the preparation of gold nanoparticles, which offers an interface for anti-CEA antibody immobilization. The fabricated immunosensor has good stability and is able to reagentlessly detect CEA over a wide range (0.005–50 ng mL⁻¹) with high reproducibility. Furthermore, the immunosensor was used for determination of CEA in human serum samples.

A label-free electrochemical sensor is easily fabricated based on stable and surface-confined Prussian blue for reagentless and sensitive detection of carcinoembryonic antigen.     

New sensing platform of poly(ester-urethane)urea doped with gold nanoparticles for rapid detection of mercury ions in fish tissue

A new electrochemical sensor has been fabricated based on the in situ synthesis of poly(ester-urethane) urea (PUU) doped with gold nanoparticles (AuNPs), and the obtained composite materials (PUU/AuNPs) were used as a new sensing platform for highly sensitive and selective detection of mercury(II) ions in fish tissue. PUU was synthesized and fully characterized by XRD, TGA, DSC, and FTIR to analyze the chemical structure, thermal stability, and morphological properties. As a polymeric structure, the PUU consists of urethane and urea groups that possess pronounced binding abilities to Hg²⁺ ions. SEM-EDX was carried out to confirm this kind of interaction. Using ferricyanide as the redox probe, PUU alone exhibited weak electrochemical signals due to its low electrical conductivity. Therefore, a new series of nanocomposites of PUU with different nanostructured materials were applied, and their electrochemical performances were evaluated. Among these materials, the PUU/AuNP-modified electrode showed high voltammetric signals towards Hg²⁺. Consequently, the parameters affecting the performance of the assay, such as electrode composition, scan rate, and sensing time, as well as the effect of electrolyte and pH were studied and optimized. The sensor showed a linear range of 5 ng mL⁻¹ to 155 ng mL⁻¹ with the regression coefficient R² = 0.986, while the calculated values of the limit of detection (LOD) and limit of quantification (LOQ) were 0.235 ng mL⁻¹ and 0.710 ng mL⁻¹, respectively. In terms of cross reactivity testing, the sensor exhibited a high selectivity against heavy metals which are commonly determined in seafood (Cd²⁺, Pb²⁺, As³⁺, Cr³⁺, Mg²⁺, and Cu²⁺). For real applications, total Hg²⁺ ions in fish tissue were determined with very high recovery and no prior complicated treatments.

A new electrochemical sensor based on poly(ester-urethane) urea doped with gold nanoparticles (PUU/AuNPs) for highly sensitive and selective detection of mercury(ii) ions in fish tissue.     

An ultrasensitive fluorescent aptasensor for detection of cancer marker proteins based on graphene oxide–ssDNA

A novel biosensing platform was developed by integrating a new ssDNA aptamer and graphene oxide (GO) for highly sensitive and selective detection of liver cancer biomarkers (alpha-fetoprotein, AFP). The key concept of this biosensing platform is that the fluorescence of dye-modified ssDNA can be effectively quenched by GO after forming the hybrid structure of graphene oxide–ssDNA (GO–ssDNA). The AFP can selectively react with GO–ssDNA and lead to the decomposition of GO–ssDNA, which results in the recovery of fluorescence, and an increase in fluorescence intensity with the increasing concentration of AFP in the range of 0 to 300 pg mL⁻¹. The linear range was obtained from 1 to 150 pg mL⁻¹ and the detection limit was 0.909 pg mL⁻¹. Moreover, this biosensing platform can be applied to serum and cell imaging for the detection of AFP. The results show that the proposed biosensor has great potential application in AFP-related clinical diagnosis and research.

A novel biosensing platform was developed by integrating a new ssDNA aptamer and graphene oxide (GO) for highly sensitive and selective detection of liver cancer biomarkers (AFP).     

Fluorescent sensing platform based on green luminescence carbon dots and AuNPs for clenbuterol detection in pork liver

In this paper, water-soluble green fluorescent carbon dots (G-CDs) were prepared using p-phenylenediamine and glutathione (GSH) as the precursors. The G-CDs exhibit excellent optical properties, and the maximum emission wavelength is located at 522 nm (under 410 nm excitation), which greatly overlaps with the absorption spectrum of AuNPs. Consequently, an effective “off–on” fluorescent sensing platform involved in G-CDs and AuNPs for detection of clenbuterol (CLB) was constructed. The fluorescence of G-CDs was strongly quenched by AuNPs due to the inner filter effect (IFE). As CLB was introduced, the quenched fluorescence intensity was recovered due to the specific interaction between the AuNPs and CLB. The recovered fluorescence intensity is linear to CLB concentration in the range of 13–270 ng mL⁻¹ with a low detection limit of 3.75 ng mL⁻¹. The prepared sensor has been successfully applied for CLB detection in pork liver and could be utilized in food analysis.

Carbon dots (G-CDs) with bright green fluorescence are synthesized by hydrothermal treatment of p-phenylenediamine and glutathione. Employing the G-CDs and AuNPs as sensing platform, a simple fluorescence sensor to detect clenbuterol was established.     

Graphitic carbon nitride and APTES modified advanced electrochemical biosensor for detection of 17β-estradiol in spiked food samples

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples. The biosensing system is based on graphitic carbon nitride (g-C₃N₄) and a conductive polymer 3-aminopropyltriethoxysilane (APTES). The proposed biosensor shows the ability to detect E2 in attomolar levels within a wide linear logarithm concentration range of 1 × 10⁻⁶ to 1 × 10⁻¹⁸ mol L⁻¹ with a limit of detection (LOD) of 9.9 × 10⁻¹⁹ mol L⁻¹. The selectivity of the developed biosensor was confirmed by conducting the DPV of similarly structured hormones and naturally occurring substances. The proposed biosensor is highly stable and applicable to detect E2 in the presence of spiked food and environmental samples with satisfactory recoveries ranging from 95.1 to 104.8%. So, the designed electrochemical biosensor might be an effective alternative tool for the detection of E2 and other endogenous substances to attain food safety.

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples.     

Mussel-inspired immobilization of Au on bare and graphene-wrapped Ni nanoparticles toward highly efficient and easily recyclable catalysts

Bimetallic nanocatalysts have been gaining huge research attention in the heterogeneous catalysis community recently owing to their tunable properties and multifunctional characteristics. In this work, we fabricated a bimetallic core–shell nanocomposite catalyst by employing a mussel-inspired strategy for immobilizing gold nanoparticles (AuNP) on the surface of nickel nanoparticles (NiNP). NiNPs obtained from the reduction of Ni(ii) were first coated with polydopamine to provide the anchoring sites towards the robust immobilization of AuNPs. The as-synthesized nanocomposite (Ni–PD–Au) exhibited outstanding catalytic activity while reducing methylene blue (MB) and 4-nitrophenol (4-NP) yielding rate constants 13.11 min⁻¹ and 4.21 min⁻¹, respectively, outperforming the catalytic efficiency of its monometallic counterparts and other similar reported catalysts by large margins. The superior catalytic efficiency of the Ni–PD–Au was attributed to the well-known synergistic effect, which was experimentally investigated and compared with prior reports. Similar bio-inspired immobilization of AuNPs was also applied on graphene-wrapped NiNPs (Ni-G) instead of bare NiNPs to synthesize another composite catalyst (Ni-G–PD–Au), which yet again exhibited synergistic catalytic activity. A comparative study between the two nanocomposites suggested that Ni–PD–Au excelled in catalytic activity but Ni-G–PD–Au provided noteworthy stability showing ∼100% efficiency over 17 repeated cycles. However, along with excellent synergistic performance, both nanocomposites demonstrated high magnetization and thermal stability up to 350 °C ascertaining their easy separation and sustainability for high-temperature applications, respectively.

Employing a bio-inspired strategy we combine Ni and Au nanoparticles into a single scaffold to achieve excellent synergistic catalysis along with high recyclability.     

A novel ultrasensitive surface plasmon resonance-based nanosensor for nitrite detection

Nitrite is a common food additive, however, its reduction product, nitrosamine, is a strong carcinogen, and hence the ultra-sensitive detection of nitrite is an effective means to prevent related cancers. In this study, different sized gold nanoparticles (AuNPs) were modified with P-aminothiophenol (ATP) and naphthylethylenediamine (NED). In the presence of nitrite, satellite-like AuNPs aggregates formed via the diazotization coupling reaction and the color of the system was changed by the functionalized AuNPs aggregates. The carcinogenic nitrite content could be detected by colorimetry according to the change in the system color. The linear concentration range of sodium nitrite was 0–1.0 μg mL⁻¹ and the detection limit was determined to be 3.0 ng mL⁻¹. Compared with the traditional method, this method has the advantages of high sensitivity, low detection limit, good selectivity and can significantly lower the naked-eye detection limit to 3.0 ng mL⁻¹. In addition, this method is suitable for the determination of nitrite in various foods. We think this novel designed highly sensitive nitrate nanosensor holds great market potential.

A satellite-like AuNP aggregate-based nitrite detection nanosensor was designed via diazotization coupling reaction and can significantly lower the naked-eye detection limit to 3.0 ng mL⁻¹. This nanosensor has important applications in food detection and cancer prevention.     

Highly sensitive and convenient aptasensor based on Au NPs@Ce-TpBpy COF for quantitative determination of zearalenone

In this work, an aptasensor based on a portable U-disk electrochemical workstation in combination with a screen-printed electrode (SPE) is demonstrated for the quantitative determination of zearalenone (ZEN). The aptamer is immobilized on Au NPs@Ce-TpBpy COF (Covalent organic frameworks), which is modified on the surface of glassy carbon electrode. ZEN specifically binds to ZEN aptamer, which hinders the electron transfer and decreases the catalytic current of Au NPs@Ce-TpBpy COF for the reduction of hydrogen peroxide, measured by chronoamperometry (i–t). The quantitative detection of ZEN toxin is realized by a decrease of the catalytic current (ΔI). Under the optimal experimental conditions, the aptamer sensor exhibited excellent sensitivity, selectivity, reproducibility. A wide linear range of 1 pg mL⁻¹–10.0 ng mL⁻¹ with a detection limit of 0.389 pg mL⁻¹ (at 3σ) was obtained. The linear equation is ΔI = 0.401 lg c + 1.948 with a correlation coefficient of 0.9906. The recovery is in the range of 93.0–104.7% for the cornflour samples. The proposed method offers a new strategy for the rapid, inexpensive, and real-time detection of ZEN.

An aptasensor based on a portable U-disk electrochemical workstation is demonstrated for the quantitative determination of zearalenone. The aptamer sensor exhibited excellent sensitivity, selectivity, reproducibility.     

Sensitive impedimetric detection of troponin I with metal–organic framework composite electrode

Metal–organic frameworks (MOFs) are promising materials for biosensing applications due to their large surface to volume ratio, easy assembly as thin films, and better biocompatibility than other nanomaterials. Their application in electrochemical biosensing devices can be realized by integrating them with other conducting materials, like polyaniline (PANI). In the present research, a composite of a copper-MOF (i.e., Cu₃(BTC)₂) with PANI has been explored to develop an impedimetric sensor for cardiac marker troponin I (cTnI). The solvothermally synthesized Cu₃(BTC)₂/PANI composite has been coated as a thin layer on the screen-printed carbon electrodes (SPE). This electroconductive thin film was conjugated with anti-cTnI antibodies. The above formed immunosensor has allowed the impedimetric detection of cTnI antigen over a clinically important concentration range of 1–400 ng mL⁻¹. The whole process of antigen analysis could be completed within 5 min. The detection method was specific to cTnI even in the co-presence of other possibly interfering proteins.

A Cu-MOF/PANI modified screen-printed electrode based immunosensing technique is described for the sensitive detection of cardiac troponin I. The sensor provides detection over a wide concentration range with a limit of detection of 0.8 ng mL⁻¹.     

Fabrication of an immunosensor for quantitative detection of breast cancer biomarker UBE2C

This work reports the design of a new electrochemical impedimetric immunosensor for the direct determination of ubiquitin-conjugating enzymes 2C (UBE2C), a potential diagnostic biomarker for breast cancer. The immunosensor was fabricated by immobilizing the capture anti-UBE2C antibody onto a polyaniline (PANI) modified glassy carbon electrode (GCE) through glutaraldehyde crosslinking. The assembly process of the immunosensor was examined using scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The fabricated immunosensor enabled the detection of recombinant human UBE2C in the range of 500 pg mL⁻¹ to 5 μg mL⁻¹. The limit of detection and limit of quantification were found to be 7.907 pg mL⁻¹ and 26.356 pg mL⁻¹, respectively. The diagnostic application of the fabricated immunosensor was explored for the analysis of breast cancer cell line MCF-7 cell extract. The immunosensor demonstrated high selectivity for UBE2C. The fabricated immunosensor also exhibited good reproducibility and storage stability.

Antibodies crosslinking on PANI modified electrode to design a highly selective immunosensor to detect UBE2C.     

Graphene oxide-Au nano particle coated quartz crystal microbalance biosensor for the real time analysis of carcinoembryonic antigen

A label-free quartz crystal microbalance (QCM) biosensor was developed for the selective and real-time estimation of carcinoembryonic antigen (CEA) through the present study. Graphene oxide-Au nanoparticles (GO-AuNPs) was in situ synthesised on the surface of the QCM electrode and the antibody of CEA (monoclonal anti-CEA from mouse) was covalently immobilized on this layer as the bioreceptor for CEA. Mercaptoacetic acid–EDC–NHS reaction mechanism was used for anti-CEA immobilization. The effect of oxygen plasma treatment of the QCM electrode surface before bioreceptor preparation on the performance of the biosensor was tested and was found promising. CEA solutions with various concentrations were analysed using the bioreceptors to estimate the sensitivity and detection limit of the biosensor. The biosensors selectively recognized and captured CEA biomolecules with a detection limit of 0.06 and 0.09 ng mL⁻¹ of CEA for oxygen plasma-treated (E2) and untreated (E1) bioreceptors, respectively. The sensitivity was estimated at 102 and 79 Hz, respectively, for E2 and E1. Clinical serum samples were analysed and the results were found in good agreement with the ELISA analysis. Long term stability was also found to be excellent. Langmuir adsorption isotherm was also conducted using the experimental results.

A label-free quartz crystal microbalance (QCM) biosensor was developed for the selective and real-time estimation of carcinoembryonic antigen (CEA) through the present study.     

Cytochrome c-multiwalled carbon nanotube and cobalt metal organic framework/gold nanoparticle immobilized electrochemical biosensor for nitrite detection

Based on cytochrome c-multiwalled carbon nanotubes (Cyt c-MWCNTs) and cobalt metal–organic frameworks/gold nanoparticles (Co-MOFs/AuNPs), an electrochemical biosensor was proposed for the detection of nitrite. Herein, Co-MOFs and AuNPs were immobilized on gold electrodes via surface layer assembly. Their advantages including large surface area and high conductivity provided an excellent platform for the immobilization of Cyt c-MWCNTs. Cyt c-MWCNTs were prepared via electrostatic adsorption and possessed good biocompatibility and superior electrocatalytic activity towards nitrite. Notably, MWCNTs and AuNPs could provide a good microenvironment for the electron transfer of Cyt c, which further significantly promoted the dispersion of MWCNTs. All of the above features led to outstanding electrochemical performance and achieved signal amplification for nitrite detection. Therefore, the biosensor displayed a linear range from 0.005 μmol L⁻¹ to 1000 μmol L⁻¹ with a detection limit of 0.0044 μmol L⁻¹ for nitrite detection. In addition, the designed biosensor exhibited excellent selectivity and could be applied in real samples.

Based on cytochrome c-multiwalled carbon nanotubes (Cyt c-MWCNTs) and cobalt metal organic frameworks/gold nanoparticles (Co-MOFs/AuNPs), an electrochemical biosensor was proposed for the detection of nitrite.     

In silico post-SELEX screening and experimental characterizations for acquisition of high affinity DNA aptamers against carcinoembryonic antigen

DNA aptamers against carcinoembryonic antigen (CEA) have been identified through the systematic evolution of ligands by exponential enrichment (SELEX) technique, but their affinity needs to be improved. In this study, an in silico approach was firstly used to screen the mutation sequences of a reported DNA aptamer (the parent aptamer, denoted as P) against CEA. The affinities of several high-score DNA mutants were determined by the biolayer interferometry technique. Finally, the newly obtained aptamers were verified in an aptasensor application. For the in silico approach, Mfold and RNA Composer were combined to generate the 3D RNA structures of the DNA mutants. The RNA structures were then modified to 3D DNA structures with the Write program. The docking model and binding ability of the 3D DNA structures with CEA were simulated and predicted with the ZDOCK program. Two mutation sequences (P-ATG and GAC-P) exhibited significantly higher ZDOCK scores than P. The dissociation constant of P-ATG and GAC-P to CEA was determined to be 4.62 and 3.93 nM respectively, obviously superior to that of P (6.95 nM). The detection limit of the P-ATG and GAC-P based aptasensors was 1.5 and 1.2 ng mL⁻¹, respectively, markedly better than that based on P (3.4 ng mL⁻¹). The consistency between the in silico and the experimental results indicates that the developed in silico post-SELEX screening approach is feasible for improving DNA aptamers. The P-ATG and GAC-P aptamers found in this study could be used for future CEA aptasensor design and fabrication, promisingly applicable for highly sensitive CEA detection and early cancer diagnosis.

High affinity DNA aptamers against carcinoembryonic antigen were selected and verified by using an in silico approach and experimental characterizations.     

Positive effects of concomitant heavy metals and their reduzates on hexavalent chromium removal in microbial fuel cells

Cr(vi) laden wastewaters generally comprise a range of multiple heavy metals such as Au(iii) and Cu(ii) with great toxicity. In the present study, cooperative cathode modification by biogenic Au nanoparticles (BioAu) reduced from aqueous Au(iii) and in situ Cu(ii) co-reduction were investigated for the first time to enhance Cr(vi) removal in microbial fuel cells (MFCs). With the co-existence of Cu(ii) in the catholyte, the MFC with carbon cloth modified with nanocomposites of multi-walled carbon nanotubes blended with BioAu (BioAu/MWCNT) obtained the highest Cr(vi) removal rate (4.07 ± 0.01 mg L⁻¹ h⁻¹) and power density (309.34 ± 17.65 mW m⁻²), which were 2.73 and 3.30 times as high as those for the control, respectively. The enhancements were caused by BioAu/MWCNT composites and deposited reduzates of Cu(ii) on the cathode surface, which increased the adsorption capacity, electronic conductivity and electrocatalytic activity of the cathode. This study provides an alternative approach for efficiently remediating co-contamination of multiple heavy metals and simultaneous bioenergy recovery.

The cooperative cathode modification by BioAu from Au(iii) and in situ Cu(ii) co-reduction enhanced Cr(vi) removal and bioelectricity generation in MFCs.     

Synthesis of an ordered nanoporous Cu/Ni/Au film for sensitive non-enzymatic glucose sensing

Ordered nanoporous Cu/Ni/Au film was prepared by electrochemical deposition and magnetron sputtering using an anodic aluminium oxide template. The fabricated porous film has a uniform hexagonal pore size structure, a long-range ordered arrangement, and a pore diameter of approximately 40 nm. Following the dissolution of the template, the independent Cu/Ni/Au film is devolved to an ITO substrate as an effective non-enzyme glucose detection sensor. The sensor has good electrocatalytic performance with two specific linear ranges of 0.5 μM to 3.0 mM and 3.0–7.0 mM and high sensitivities of 4135 and 2972 μA mM⁻¹ cm⁻², respectively. The lower detection limit was 0.1 μM with a signal-to-noise ratio of 3. Additionally, the sensor features excellent selectivity and stability. These satisfactory results indicate that Cu/Ni/Au film is a promising platform for the development of non-enzymatic glucose sensors.

Ordered nanoporous Cu/Ni/Au film prepared by template method could be transferred and used as an effective glucose sensor.     

Facile one-pot method of AuNPs/PEDOT/CNT composites for simultaneous detection of dopamine with a high concentration of ascorbic acid and uric acid

In this research, a facile one-pot method was used to synthesize gold/poly-3,4-ethylene-dioxythiophene/carbon nanotube (AuNPs/PEDOT/CNTs) composite material. The composite material was investigated by Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Then the synthesized nanocomposite material was dropped on a bare glassy carbon electrode (GCE) to improve the detection performance of dopamine with a high concentration of ascorbic acid and uric acid. The electrochemical behavior of AuNPs/PEDOT/CNTs/GCE was studied by Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimum conditions, AuNPs/PEDOT/CNTs/GCE showed a good linear response in the concentration range from 9.14 to 29.704 μM with a detection limit (LOD) and sensitivity of 0.283 μM and 1.557 μA μM⁻¹, respectively. This sensor was applied to detect practical samples with good average recovery. It also exhibited good reproducibility and stability.

A facile one-pot method was used to synthesize ternary composite material. This modified electrode exhibited good ability of detecting dopamine. It also exhibited excellent anti-interference ability and stability.      

In situ electrochemical activation as a generic strategy for promoting the electrocatalytic hydrogen evolution reaction and alcohol electro-oxidation in alkaline medium

In situ electrochemical activation as a new pre-treatment method is extremely effective for enhanced electrocatalytic performances for different applications. With the help of this method, in situ surface modification of electrocatalyst is achieved without using pre-made seeds or complex synthesis procedure. Herein, with the purpose of finding an in situ and simple electrochemical activation protocol, the green synthesis of Au/Pd nanoparticles (AuPd) by means of polyoxometalate (POM) is reported. Structural analysis of the AuPd nanohybrid unveil the Au-core/Pd-shell structure which surrounded by POM. We propose a novel cathodic electrochemical activation in phosphate buffer solution which can greatly boost the electrocatalytic activity of the as-prepared AuPd and Pd electrocatalyst not only for hydrogen evolution reaction (HER) as a model of electro-reduction, but also for methanol and ethanol electro-oxidation reaction (MOR & EOR). For the HER in 1 M NaOH solution, after the electrochemical activation, the needed potential to drive a geometrical current density of 10 mA cm⁻² significantly decreases from – 400 mV vs. the reversible hydrogen electrode (RHE) to −290 mV vs. RHE. For the EOR and MOR, electrochemically activated AuPd realized 3.4- and 2.9- fold increase in mass current density (mA mg_Pd⁻¹) with respect to the pristine AuPd electrocatalyst, respectively.

In situ electrochemical activation as a new pre-treatment method is extremely effective for enhanced electrocatalytic performances for different applications.     

Electrochemical detection of C-reactive protein using functionalized iridium nanoparticles/graphene oxide as a tag

C-reactive protein (CRP) has become a recognized indicator of inflammation. CRP concentration in serum is an important indicator for monitoring early heart damage, and it is also a newly discovered coronary heart disease-associated inflammatory factor. A conductive nano-hybrid material composed of Au NPs and ionic liquid functionalized molybdenum disulfide (Au NPs/IL-MoS₂) was prepared and utilized to immobilize primary CRP antibodies. Subsequently, 1,5-diaminonaphthalene (DN) was adsorbed onto graphene oxide (GO) through π–π stacking, which was used to load iridium nanoparticles (Ir NPs) as a tag to label secondary CRP antibodies. The large surface area of Au NPs/IL-MoS₂ and the excellent electrocatalytic properties of Ir NPs/GO-DN toward the reduction of H₂O₂ resulted in a highly sensitive assay for CRP antigens. This immunosensor exhibited wide linear ranges from 0.01 to 100 ng mL⁻¹ and a lower detection of limit of 3.3 pg mL⁻¹ (S/N = 3). This CRP immunosensor can be applied in real serum sample analysis with satisfactory results, indicating that the immunosensor has potential applications in biomedical detection.

Ir NPs@GO-DN was used as a tag to label CRP antibody to construct a sandwich CRP immunosensor.     

A thio-β-cyclodextrin functionalized graphene/gold nanoparticle electrochemical sensor: a study of the size effect of the gold nanoparticles and the determination of tetrabromobisphenol A

In this study, a novel tetrabromobisphenol A (TBBPA) sensor was fabricated based on a CTAB-capped gold nanoparticle (AuNPs)-thio-β-cyclodextrin (SH-β-CD)/graphene oxide modified glassy carbon electrode (GCE). The peak current of TBBPA was dramatically enhanced by the AuNPs with a diameter of 6.2 nm on the modified electrodes compared with the other sized particles (10.1 or 16.1 nm). To further improve the electrochemical performance of the modified electrode, the influence of pH of the buffer solution and the accumulation time on the determination were investigated. The optimum pH and accumulation time were 7.0 and 180 s, respectively. The developed sensor exhibited good reproducibility, and excellent sensitivity and selectivity, showing a low detection limit (1.2 × 10⁻⁹ mol L⁻¹) and a linear range from 1.5 × 10⁻⁸ to 7 × 10⁻⁶ mol L⁻¹. In addition, a possible oxidization mechanism of TBBPA was also discussed. Finally, this sensor was successfully applied to detect TBBPA in water samples, and the results were consistent with those acquired by high-performance liquid chromatography.

In this study, a novel tetrabromobisphenol A (TBBPA) sensor was fabricated based on a CTAB-capped gold nanoparticle (AuNP)-thio-β-cyclodextrin (SH-β-CD)/graphene oxide modified glassy carbon electrode (GCE).