Electronic Transmission Rate Research Articles

Inorganic/Organic Doped Carbon Aerogels As Biosensing Materials for the Detection of Hydrogen Peroxide

In this article, three different inorganic/organic doped carbon aerogel (CA) materials (Ni-CA, Pd-CA, and Ppy-CA) were, respectively, mixed with ionic liquid (IL) to form three stable composite films, which were used as enhanced elements for an integrated sensing platform to increase the surface area and to improve the electronic transmission rate. Subsequently, the effect of the materials performances such as adsorption, specific surface area and conductivity on electrochemistry for myoglobin (Mb) was discussed using N2 adsorption-desorption isotherm measurements, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Moreover, they could act as sensors toward the detection of hydrogen peroxide (H2O2) with lower detection limits (1.68 μM, 1.02 μM, and 0.85 μM, for Ni-CA/IL/Mb-CPE, Pd-CA/IL/Mb-CPE, and Ppy-CA/IL/Mb-CPE, respectively) and smaller apparent Michaelis-Menten constants KM. The results indicated that the electroconductibility of the doped CA materials would become dominant, thus playing an important role in facilitating the electron transfer. Meanwhile, the synergetic effect with [BMIm]BF4 IL improved the capability of the composite inorganic/organic doped CA/IL matrix for protein immobilization. This work demonstrates the feasibility and the potential of a series of CA-based hybrid materials as biosensors, and further research and development are required to prepare other functional CAs and make them valuable for more extensive application in biosensing.

Label-free immunosensor based on Pd nanoplates for amperometric immunoassay of alpha-fetoprotein

In this paper, Pd nanoplates were used as a kind of electrode materials for fabrication of an electrochemical immunosensor, which was applied for detection of cancer biomarker alpha-fetoprotein (AFP). Thanks to the unique structure and properties of Pd nanoplates, the antibody of AFP (Ab) was effectively immobilized onto the surface of the Pd nanoplates modified glassy carbon electrode (GCE). Moreover, the good electrochemical properties of Pd nanoplates greatly improved the electronic transmission rate and enhanced the electrochemical signal, which led to an increase of the detection sensitivity. Based on the specific antibody–antigen interaction, a label-free immunosensor based on Pd nanoplates was developed for sensing of AFP. The current method allows us to detect AFP over a wide concentration range from 0.01 to 75.0ng/mL with a detection limit of 4pg/mL. The proposed immunosensor has been used to determine AFP in human serum with satisfactory results.

A New Method of Real-Time Detecting the Chlorophyll Based on Hover Wing UAV

A fluorescent real-time detection technology parameters of the chlorophyll radiation LED method using with fluorescent MINIPAM based on impulse, modulation, is introduced. The using of programming power to provide a constant flow of the list of output, LED by a matrix as chlorophyll are fluorescent light. The using of apparatus in plant MINIPAM fluorescent light system II of the steady state Fs, a fluorescent light to the next largest fluorescent Fm',a combination of the environment, and tracking control system of measurement and comprehensive analysis of environmental factors to the real quantum efficiency, actual electronic transmission rate for parameters. MINIPAM fluorescent apparatus with the upper machine, and can be real time monitoring.

Au–Pt nanoparticle-based electrochemiluminescence immunoassay of a cancer biomarker using ZnO nanospheres coated with CdTe quantum dots as labels

An easy-to-operate sandwich-type electrochemiluminescence (ECL) immunosensor was constructed on a glassy carbon electrode in this work. In order to fabricate a high-performance sensor, Au–Pt nanoparticles were electrodeposited onto the electrode surface, where they acted as the immunosensing platform, greatly improving the electronic transmission rate and increasing the amount of PSA primary antibody (PSA-Ab1) present. To increase the sensitivity of the sensor even further, stable CdTe/ZnO nanoparticles were synthesized, characterized by scanning electron microscopy, and then employed to label PSA secondary antibody (PSA-Ab2). When the appropriate antigen was recognized by this antibody, PSA-Ab1, PSA, and PSA-Ab2 formed a sandwich-type immunocomplex that produced ECL in the presence of S2O8 2− coreactant. Under optimal conditions, the ECL immunosensor showed a good linear range (0.0025–100.0 ng cm−3) and a low detection limit (1.0 pg cm−3). It was therefore demonstrated that the proposed strategy is a repeatable, stable, and potent method that can be expanded to detect other proteins. .

Ultrasensitive electrochemical immunoassay for carcinoembryonic antigen based on three-dimensional macroporous gold nanoparticles/graphene composite platform and multienzyme functionalized nanoporous silver label

Three-dimensional macroporous gold nanoparticles/graphene composites (3D-AuNPs/GN) were synthesized through a simple two-step process, and were used to modify working electrode sensing platform, based on which a facile electrochemical immunoassay for sensitive detection of carcinoembryonic antigen (CEA) in human serum was developed. In the proposed 3D-AuNPs/GN, AuNPs were distributed not just on the surface, but also on the inside of graphene. And this distribution property increased the area of sensing surface, resulting in capturing more primary antibodies as well as improving the electronic transmission rate. In the presence of CEA, a sandwich-type immune composite was formed on the sensing platform, and the horseradish peroxidase-labeled anti-CEA antibody (HRP-Ab2)/thionine/nanoporous silver (HRP-Ab2/TH/NPS) signal label was captured. Under optimal conditions, the electrochemical immunosensor exhibited excellent analytical performance: the detection range of CEA is from 0.001 to 10ngmL−1 with low detection limit of 0.35pgmL−1 and low limit of quantitation (LOQ) of 0.85pgmL−1. The electrochemical immunosensor showed good precision, acceptable stability and reproducibility, and could be used for the detection of CEA in real samples. The proposed method provides a promising platform of clinical immunoassay for other biomolecules

Ultrasensitive electrochemiluminescent immunosensor based on dual signal amplification strategy of gold nanoparticles-dotted graphene composites and CdTe quantum dots coated silica nanoparticles

A facile and ultrasensitive electrochemiluminescent (ECL) immunosensor for detection of prostate-specific antigen (PSA) was designed by using CdTe quantum dots coated silica nanoparticles (SiO2@QDs) as bionanolabels. To construct such an electrochemiluminescence immunosensor, gold nanoparticles-dotted graphene composites were immobilized on the working electrode, which can increase the surface area to capture a large amount of primary antibodies as well as improve the electronic transmission rate. The as-prepared SiO2@QDs used as bionanolabels, showed good ECL performance and good ability of immobilization for secondary antibodies. The approach provided a good linear response ranging from 0.005 to 10 ng mL(-1) with a low detection limit of 0.0032 ng mL(-1). Such immunosensor showed good precision, acceptable stability, and reproducibility. Satisfactory results were obtained for determination of PSA in human serum samples. Therefore, the proposed method provides a new promising platform of clinical immunoassay for other biomolecules.

Three-dimensional nanoflower-like MnO2 functionalized graphene as catalytically promoted nanolabels for ultrasensitive electrochemiluminescence immunoassay

A novel electrochemiluminescence (ECL) immunosensor based on the peroxydisulfate solution for detection of prostate-specific antigen (PSA) has been developed. In this work, gold nanoparticles (AuNPs) were electrodeposited on the glassy carbon electrode surface, which could increase the surface area to capture a large amount of primary antibodies as well as to improve the electronic transmission rate. The as-prepared bionanolabels, three-dimensional (3D) nanoflower-like MnO2 functionalized graphene (GN/MnO2), with novel hybrid architecture were initially fabricated via electrostatic interaction. Then, to provide an effective matrix for antibody immobilization with good stability and bioactivity, the novel materials were modified by AuNPs with the aid of poly (diallyldimethylammonium chloride) via a simple sonication-induced assembly method. In this immunosensor, MnO2 with the characteristics of well electrochemical behavior, low cost, and environmental-friendly, is used as a substitute for horseradish peroxidase to catalyze H2O2 to produce O2, and its 3D nanoflower-like structure is beneficial for the unparallel surface-to-volume ratio. Furthermore, a simple, low-cost and portable home-made potential transformer was utilized in this system to take the place of conventional electrochemical workstation. With a sandwich-type immunoassay format, the amount of functionalized GN/MnO2 labeled antibodies increased with the increment of antigens in the samples, which implied that the ECL signals enhanced with the increase of in situ generated O2 due to the enhancive catalysis of MnO2 to the H2O2. The immunosensor displayed excellent analytical performance for the detection of PSA in the range of 0.005–10ngmL−1 with a detection limit of 2.5pgmL−1 at 3σ. Moreover, the proposed method showed good precision, acceptable stability and reproducibility, and could be used for the detection of PSA in real samples. The proposed method provides a new promising platform of clinical immunoassay for other biomolecules.

Ultrasensitive electrochemical immunosensors for clinical immunoassay using gold nanoparticle coated multi-walled carbon nanotubes as labels and horseradish peroxidase as an enhancer

A novel electrochemical immunosensor for the ultrasensitive detection of α-fetoprotein (AFP) is described with the use of a gold nanoparticle/(3-mercaptopropyl) trimethoxysilane modified electrode as a desirable platform and gold nanoparticle functionalized multi-walled carbon nanotube (MWCNT) nanocomposite labeled secondary antibodies (Ab2) as a signal tag. At first, gold nanoparticles (AuNPs) were attached on the MWCNTs surface using poly(diallyldimethylammoniumchloride) (PDDA) as a linkage reagent to obtain AuNP–MWCNT nanocomposites. Subsequently, horseradish peroxidase (HRP) and thionine (Thi) labeled secondary antibodies (Thi-Ab2) were used to bind AuNP–MWCNT nanocomposites with a high load amount and good biological activity. Moreover, the immunosensor can provide amplified signals because of the increased surface area and biocompatibility of AuNP–MWCNT nanocomposites. On the other hand, the AuNP functionalized (3-mercaptopropyl) trimethoxysilanes (MPTS) were used for the biosensor platform to increase the surface area as well as improving the electronic transmission rate to capture a large amount of primary antibodies (Ab1). Thus, amplified signals can be obtained by an electrochemical sandwich immunoassay protocol in the presence of H2O2. The proposed sensing strategy provides a wide linear dynamic range from 0.01 to 50 ng mL−1 with a low detection limit of 3 pg mL−1 (S/N = 3). Significantly, the developed immunoassay method showed a good stability, selectivity and reproducibility.

Ultrasensitive electrochemiluminescence detection of lengthy DNA molecules based on dual signal amplification

Aimed at the facile detection of lengthy DNA molecules, an easily operated sandwich-type electrochemiluminescence (ECL) DNA biosensor was constructed on a glassy carbon electrode (GCE) based on CdTe quantum dots coated hollow ZnO nanoparticles (CdTe-ZnO NPs)-S(2)O(8)(2-) ECL system in this work. To fabricate a high-performance protocol, the GCE surface was successively modified by graphene nanosheet (GS), carbon nanotube (CNT) and gold nanoparticles (AuNPs) to form AuNPs dotted CNT-GS composites (Au@CNT-GS) platform, which improved the electronic transmission rate as well as increased the amount of immobilized capture probe CMV-F (S(1)). For further ultrasensitive, stable and low-potential ECL detection, CdTe-ZnO NPs were synthesized, and employed to label signal probe T7 promoter (S(3)). Based on the hybridization effect, the immobilized capture probe S(1), target DNA and labeled signal probe S(3) formed a sandwich-type DNA complex, which produced the ECL emission in the presence with S(2)O(8)(2-) coreactant. Under optimal conditions, the DNA ECL biosensor showed a good linear range over 10(-14) M to 10(-19) M with a low detection limit of 0.61 × 10(-19) M. The proposed strategy demonstrates a reproducible, stable, and potent method that can be expanded to detect the genome which exists in living cells.

Gold–silver nanocomposite-functionalized graphene sensing platform for an electrochemiluminescent immunoassay of a tumor marker

A novel electrochemiluminescence (ECL) immunosensor based on a prepared 3D paper device was designed for the sensitive detection of a tumor marker in human serum by using CdTe quantum dot coated carbon microspheres (QD@CMs) as bionanolabels. To construct such an ECL immunosensor, gold–silver nanocomposite-functionalized graphene was prepared and used as a sensing platform, which increased the surface area to capture a large number of primary antibodies as well as improving the electronic transmission rate. With the employment of the as-prepared QD@CMs as bionanolabels, a good ECL performance (excellent precision and sensitivity) was exhibited through a sandwich-type immunoassay. To examine the signal amplification of the immunoassay, the analytical properties of various immunosensor platforms and labels were compared in detail. As a proof-of-concept, cancer antigen 125 was used as a model analyte and satisfactory results were obtained. Therefore, the proposed method provides a new promising platform for clinical immunoassays of other biomolecules.

An integrated sensing system for detection of cholesterol based on TiO2–graphene–Pt–Pd hybridnanocomposites

In this article, we used the TiO2–graphene–Pt–Pd hybrid nanocomposites (TGPHs) as an enhanced element of the integrated sensing platform for increasing the surface area as well as improving the electronic transmission rate. Subsequently, Au nanoparticles (AuNPS) and cholesterol oxidase (ChOx) were successively self-assembled to TGPHs with high load amount and superior biological activity. The morphology of TGPHs and stepwise fabrication processes were characterized with cyclic voltammetry (CV), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the efficiently catalytic ability of TGPHs and AuNPS, the fabricated biosensor exhibited wide linear ranges of responses to cholesterol in the concentration ranges of 5.0×10−8−5.9×10−4M, the limit of detection was 0.017μM (S/N=3). The response time was less than 7s and the Michaelis–Menten constant (Kmapp))was found as 0.21mM. The fabricated biosensor was further tested using real food samples egg, meat, margarine and fish oil, showing that the biosensor has the potential to be used as a facile cholesterol detection tool in food and supplement quality control.

Multifunctional Fe3O4 core/Ni–Al layered double hydroxides shell nanospheres as labels for ultrasensitive electrochemical immunoassay of subgroup J of avian leukosis virus

A novel electrochemical immunosensor for ultrasensitive detection of subgroup J of avian leukosis virus (ALVs-J) was designed by using graphene sheets (GS)-layered double hydroxides (LDHs) composites modified electrode with multifunctional Fe3O4 core/Ni–Al LDHs shell (LDHs@Fe3O4) nanospheres as labels. At first, the GS-LDHs were used for the immunosensor platform for improving the electronic transmission rate as well as increasing the surface area to capture a large amount of primary antibodies (Ab1). After that, ferrocene (Fc), secondary antibodies (Ab2) and horseradish peroxidase (HRP) multifunctional LDHs@Fe3O4 nanospheres were used as labels with high load amount and good biological activity. Subsequently, in presence of H2O2, amplified signals were obtained by an electrochemical sandwich immunoassay protocol. To embody the signal amplification property of the protocol, the analytical properties of various immunosensor platform and labels were compared in detail. Under optimal conditions, the reduction peak currents of the electrochemical immunosensor were proportional to the ALVs-J concentration over the range from 102.32 to 105.50 TCID50/mL with a low detection limit (180 TCID50/mL, S/N=3). The resulting immunosensor also displayed a good selectivity, reproducibility and stability.

Ultrasensitive electrochemical immunosensor based on Au nanoparticles dotted carbon nanotube–graphene composite and functionalized mesoporous materials

A facile and sensitive electrochemical immunosensor for detection of human chorionic gonadotrophin (hCG) was designed by using functionalized mesoporous nanoparticles as bionanolabels. To construct high-performance electrochemical immunosensor, Au nanoparticles (AuNPs) dotted carbon nanotubes (MWCNTs)–graphene composite was immobilized on the working electrode, which can increase the surface area to capture a large amount of primary antibodies (Ab1) as well as improve the electronic transmission rate. The as-prepared bionanolabels. composed of mesoporous silica nanoparticles (MCM-41) coated with AuNPs through thionine linking, showed good adsorption of horseradish peroxidase-labeled secondary anti-hCG antibody. Interlayer thionine was not only a bridging agent between MCM-41 and AuNPs but also an excellent electron mediator. The approach provided a good linear response range from 0.005 to 500mIUmL−1 with a low detection limit of 0.0026mIUmL−1. The immunosensor showed good precision, acceptable stability and reproducibility. Satisfactory results were obtained for determination of hCG in human serum samples. The proposed method provides a new promising platform of clinical immunoassay for other biomolecules.

First-Principles Study on Transport Properties of Saturated Single Crystalline GaN Nanotubes

Electronic structures and transport properties of the saturated single crystalline GaN nanotubes with 0.92 nm inner diameter and different wall thickness have been investigated by using first-principles and non-equilibrium green's function (NEGF). The result shows, the energy gap of the saturated single crystalline nanotubes changed from 0.2933 to 2.8442 eV. The saturated single crystalline GaN nanotubes have the direct band gap and the band gap decreases with the increase of wall thickness of nanotubes. The electronic density of state and the electronic transmission spectra of two-probe system have pulse-type sharp peak, the change of electronic density of state is in accord with electronic transmission rate. I-V characteristics of two-probe systems reflect that the saturated single-wall GaN nanotube and the saturated single-layer GaN nanotube are semiconducting properties, and the saturated double-layer GaN nanotube appears metallic behavior.

Green synthesis of silver and gold nanoparticles using Rosa damascena and its primary application in electrochemistry

Biosynthesis and characterizations of nanoparticles have become an important branch of nanotechnology. In this paper, green synthesis of gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) using the flower extract of Rosa damascena as a reducing and stabilizing agent, has been discussed. This approach is simple, cost-effective and stable for a long time, reproducible at room temperature and in an eco-friendly manner to obtain a self-assembly of AuNPs and AgNPs. The resulting nanoparticles are characterized using UV–vis, TEM, XRD and FT-IR spectroscopic techniques. A modified glassy carbon electrode using AuNPs (AuNPs/GCE) was investigated by means of cyclic voltammetry in a solution of 0.1 M KCl and 5.0×10 −3 M [Fe(CN) 6] 3−/4−. The results show that electronic transmission rate between the modified electrode and [Fe(CN) 6] 3−/4− increased.

Glucose oxidase and ferrocene labels immobilized at Au/TiO 2 nanocomposites with high load amount and activity for sensitive immunoelectrochemical measurement of ProGRP biomarker

Progastrin releasing-peptide (ProGRP) is a sensitive, specific, and reliable tumor marker with small cell lung cancer (SCLC), which may indicate an early tendency of cancer metastasis, causing high mortality rate. Thus, aiming for a more convenient assay system of SCLC, a novel immunoelectrochemical measurement for sensitive detection of ProGRP was developed in this work via Au nanoparticle/graphene modified immunosensor with ferrocene and glucose oxidase-multifunctionalized Au/TiO 2 nanocomposites as a trace label. At first, Au nanoparticles (nano-Au) were attached on the TiO 2 nanoparticles surface by using 3-aminopropyltriethoxy silane (APTES) as linkage reagent to obtain Au/TiO 2 nanocomposites (nano-Au/TiO 2). Next, glucose oxidase (GOD) and ferrocene labeled secondary antibodies (Fc-Ab 2) were used to bind Au/TiO 2 nanocomposites with high load amount and good biological activity, and because the increased surface area and biocompatibility of nano-Au/TiO 2, the electrode can provide amplified signals. On the other hand, the nano-Au functionalized graphene sheets (GS) were used for the biosensor platform for increasing the surface area as well as improving the electronic transmission rate to capture a large amount of primary antibodies (Ab 1). Then in presence of glucose, amplified signals can be obtained by an electrochemical sandwich immunoassay protocol. Based on the proposed immunosensor, the current is linear with the concentration of ProGRP being within a concentration range from 10.0 to 500 pg/mL with a limit of detection down to 3.0 pg/mL (S/N = 3).

Barbated Skullcup herb extract-mediated biosynthesis of gold nanoparticles and its primary application in electrochemistry

The design, synthesis, characterization and application of biologically synthesized nanomaterials have become an important branch of nanotechnology. In this paper, we report the extracellular synthesis of gold nanoparticles using Barbated Skullcup (BS) herb (a dried whole plant of Scutellaria barbata D. Don) as the reducing agent. After exposing the gold ions to BS herb extract, rapid reduction of gold ions is observed leading to the formation of gold nanoparticles in solution. UV–vis spectrum of the aqueous medium containing gold nanoparticles showed a peak at around 540 nm. Transmission electron microscopy (TEM) micrograph analysis of the gold nanoparticles indicated that they were well-dispersed and ranged in size 5–30 nm. When the gold nanoparticles were modified on the glassy carbon electrode (GCE), it could enhance electronic transmission rate between the electrode and the p-nitrophenol.