Biofunctional photoelectrochemical/electrochemical immunosensor based on BiVO4/BiOI-MWCNTs and Au@PdPt for alpha-fetoprotein detection.

A biofunctional immunosensor combining photoelectrochemical (PEC) and electrochemical (EC) was proposed for the quantitative detection of the liver cancer marker alpha-fetoprotein (AFP) in human blood. BiVO4/BiOI-MWCNTs photoactive materials were first prepared on conductive glass FTO, and the photoelectrode was functionalized by chitosan and glutaraldehyde. Then, the AFP capture antibody (Ab1) was successfully modified on the photoelectrode, and the label-free rapid detection of AFP antigen was achieved by PEC. In addition, Au@PdPt nanospheres were also used as a marker for binding to AFP detection antibody (Ab2). Due to the excellent catalytic properties of Au@PdPt in EC reaction, a signal increase in the EC response can be achieved when Ab2 binds to the AFP antigen, which ensures high sensitivity for the detection of AFP. The detection limits of PEC and EC are 0.050 pg/mL and 0.014 pg/mL, respectively. The sensor also possesses good specificity, stability and reproducibility, shows excellent performance in the detection of clinical samples and has good clinical applicability.

Synthesis of InAl-alloyed Ga2O3 nanowires for self-powered ultraviolet detectors by a CVD method.

Ga2O3 is a kind of wide-band gap semiconductor, which has great potential in deep ultraviolet detection because of its high efficiency and fast response. Doping can improve the photoelectric properties of Ga2O3 materials. In this paper, In and Al elements alloyed Ga2O3 nanowires (InAl-Ga2O3 NWs) were successfully grown on p-GaN using a cost-effective chemical vapor deposition method and a vertical structure. The GaN/InAl-Ga2O3 NWs p-n self-powered wide-gap UV photodetector (PD) was constructed based on sputtered gold film as the bottom and top electrodes, and spin coated with polymethyl methacrylate as the insulating layer in the vertical direction. The GaN/InAl-Ga2O3 UV PD exhibits excellent performances, including an extremely low dark current of 0.015 nA, a maximum photocurrent of about 16 nA at zero-bias voltage under 265 nm illumination, and a light-to-dark current ratio greater than 103. The responsivity is 0.94 mA W-1, the specific detectivity is 9.63 × 109 jones, and the good fast response/attenuation time is 31.2/69.6 ms. The self-powered characteristics are derived from the internal electric field formed between p-type GaN and n-type InAl-Ga2O3 NWs, which is conducive to the rapid separation and transfer of photogenerated carriers. This work provides an innovative mechanism of high-performance metal oxide nanowires for the application of p-n junction photodetectors, which can operate without any external bias.

Low-cost wavefront shaping via the third-order correlation of light fields.

In this Letter, inspired by the ghost imaging technique, we propose a wavefront shaping technique based on the third-order correlation of light fields (TCLF). Theoretically, we prove that if the light field fluctuation can be modeled by a complex Gaussian random process with a non-zero mean, the conjugate complex amplitude of the object and a focusing phase factor can be obtained by TCLF when using a single-point detector, which can support wavefront shaping. Experiments demonstrate that TCLF can achieve high-resolution wavefront shaping for scattered fields and scattering-assisted holography without additional operations such as optimization and phase shifting.

Electrochemical immunosensor based on Fe3O4/MWCNTs-COOH/AuNPs nanocomposites for trace liver cancer marker alpha-fetoprotein detection.

An electrochemical biosensor based on iron tetroxide (Fe3O4)/carboxylated carbon nanotubes (MWCNTs-COOH)/gold nanoparticles (AuNPs) was designed for the detection of alpha-fetoprotein (AFP), which is often used as an important indicator for the early clinical diagnosis of liver cancer markers. The Fe3O4/MWCNTs-COOH nanocomposite was synthesized by a solvothermal method and it combined with gold nanoparticles (AuNPs) deposited at the constant potential on a glassy carbon electrode to form Fe3O4/MWCNTs-COOH/AuNPs, which intensifies the electrical signal while the large active sites enable more stable immobilization of the AFP monoclonal antibodies on the electrode. The electrochemical performance of Fe3O4/MWCNTs-COOH/AuNPs was investigated in detail and the electrochemical response signal after the immune reaction with the AFP antigen-antibody was recorded. The peak current Ip of the response signal is linearly proportional to the lgcAFP in the range of 1 pg mL-1-10 µg mL-1, with a detection limit of 1.09034 pg mL-1 and good performance in clinical sample testing. The proposed sensor has shown great application and development potential in clinical medicine field.

Simultaneous measurement of trace dimethyl methyl phosphate and temperature using all fiber Michaelson interferometer cascaded FBG.

All fiber Michaelson interferometer cascaded fiber Bragg grating (FBG) sensor for simultaneous measurement of trace dimethyl methyl phosphate and temperature is proposed. One end of the four-core fiber (FCF) is spliced with a multimode fiber (MMF), the other end is flattened and evaporated with silver film to enhance reflection, and the Michelson interference structure is formed. The grating is engraved in the single-mode fiber (SMF) core and spliced with MMF, then the Michelson interference cascaded FBG, FBG-MMF-FCF sensor is obtained. The sensing film, MnCo2O4 is coated on the surface of FCF, and the structure, elemental composition and morphology of MnCo2O4 were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The sensitivity and the detection limit of DMMP are 86.44 dB/ppm and 0.1767 ppb, respectively. The response/recovery time is about 14/10 s. the temperature sensitivity can be compensated and calculated as 0.069 nm/°C. The sensor has good selectivity and stability, and has a good application prospect in high sensitivity detection of trace DMMP vapor.

Hollow terbium metal-organic-framework spheres: preparation and their performance in Fe3+ detection.

Hollow metal-organic framework (MOF) micro/nanostructures have been attracting a great amount of research interest in recent years. However, the synthesis of hollow metal-organic frameworks (MOFs) is a great challenge. In this paper, by using 1,3,5-benzenetricarboxylic acid (H3BTC) as the organic ligand and 2,5-thiophenedicarboxylic acid (H2TDC) as the competitive ligand and protective agent, hollow terbium MOFs (Tb-MOFs) spheres were synthesized by a one-pot solvothermal method. By comparing the morphology of Tb-MOFs in the presence and absence of H2TDC, it is found that H2TDC plays a key role in the formation of the hollow spherical structure. Single crystal analyses and element analysis confirm that H2TDC is not involved in the coordination with Tb3+. Interestingly, Tb-MOFs can be used as the luminescent probes for Fe3+ recognition in aqueous and N,N-dimethylformamide (DMF) solutions. In aqueous solution, the quenching constant (K SV) is 5.8 × 10-4 M-1, and the limit of detection (LOD) is 2.05 µM. In DMF, the K SV and LOD are 9.5 × 10-4 M-1 and 0.80 µM, respectively. The sensing mechanism is that the excitation energy absorption of Fe3+ ions reduces the energy transfer efficiency from the ligand to Tb3+ ions.

Synthesis of vertically-aligned large-area MoS2nanofilm and its application in MoS2/Si heterostructure photodetector.

Van der Waals heterostructures based on the combination of 2D transition metal dichalcogenides and conventional semiconductors offer new opportunities for the next generation of optoelectronics. In this work, the sulfurization of Mo film is used to synthesize vertically-aligned MoS2nanofilm (V-MoS2) with wafer-size and layer controllability. The V-MoS2/n-Si heterojunction was fabricated by using a 20 nm thickness V-MoS2, and the self-powered broadband photodetectors covering from deep ultraviolet to near infrared is achieved. The device shows superior responsivity (5.06 mA W-1), good photodetectivity (5.36 × 1011Jones) and high on/off ratioIon/Ioff(8.31 × 103at 254 nm). Furthermore, the V-MoS2/n-Si heterojunction device presents a fast response speed with the rise time and fall time being 54.53 ms and 97.83 ms, respectively. The high photoelectric performances could be attributed to the high-quality heterojunction between the V-MoS2and n-Si. These findings suggest that the V-MoS2/n-Si heterojunction has great potential applications in the deep ultraviolet-near infrared detection field, and might be used as a part of the construction of integrated optoelectronic systems.

Cadmium-ion detection: a comparative study for a SnO2, MoS2, SnO2/MoS2, SnO2-MoS2 sensing membrane combination with a fiber-optic Mach-Zehnder interferometer.

A novel fiber-optic Mach-Zehnder interferometer based on SnO2, MoS2, SnO2/MoS2, and SnO2-MoS2 sensing film for cadmium-ion (Cd2+) detection is proposed and fabricated. The photonic-crystal fiber (PCF) is sandwiched between the no-core-fiber-1 (NCF1) and no-core-fiber-2 (NCF2), forming the Mach-Zehnder interferometer with the NCF1-PCF-NCF2 structure, which is regarded as the sensing unit. The SnO2, MoS2, SnO2/MoS2, and SnO2-MoS2 sensing films are, respectively, coated on the surface of two NCFs' claddings. The comparative experiment results of the sensors with four membranes (SnO2, MoS2, SnO2/MoS2, SnO2-MoS2) show that the sensors have good sensing performance for Cd2+ in the concentration range of 0-100 µM. When these sensing films adsorbed Cd2+, the monitoring wavelength shows blueshift of 0.6931 nm, 1.0252 nm, 1.9505 nm, respectively, and redshift of 3.0258 nm, and the sensitivities are 6.931 pm/µM, 10.252 pm/µM, 19.505 pm/µM, and 30.258 pm/µM, respectively. The sensor with SnO2-MoS2 bilayer film exhibits the optimal response to Cd2+ with excellent selectivity and stability. The proposed sensor has the advantages of simple structure, easy fabrication, small size, etc., having potential application in the monitoring of Cd2+ in aqueous solution.

Hydrogen sulfide gas sensor based on copper/graphene oxide coated multi-node thin-core fiber interferometer.

A hydrogen sulfide gas sensor based on a copper/graphene oxide (Cu/GO) coated multi-point thin-core fiber Mach-Zehnder interferometer is proposed and experimentally demonstrated. The single-mode fiber (SMF) is sandwiched between the thin-core-fiber-1 (TCF-1) and thin-core-fiber-2 (TCF-2), and the SMF-TCF-1-SMF-TCF-2-SMF Mach-Zehnder interferometer is obtained. In order to detect the concentration of hydrogen sulfide, Cu/GO composite sensitive film was coated on the outside surface of two thin-core fibers. When the composite film absorbs the gases, it leads to a change of the effective refractive index of the cladding and causes the regular shift of dip wavelength. The result indicates that the thickness of the sensitive film is 1.6 µm. With the increase of concentration of hydrogen sulfide, the transmission spectra appear blueshift in the range of 0-60 ppm H2S. The linearity of 0.9884 and sensitivity of 4.83 pm/ppm are achieved. In addition, the dynamic response time and recovery time of the hydrogen sulfide sensor are about 32 s and 52 s, respectively. This sensor has the advantages of the small size, simple structure, and easy manufacture, and it is suitable for the detection of trace hydrogen sulfide.

DNA breakage induced by piceatannol and copper(II): Mechanism and anticancer properties.

Piceatannol (3,3',4,5'-tetrahydroxy-trans-stilbene; Pice), found in a variety of plant sources including grapes, red wine, peanuts and rhubarb, is known as a metabolite and analog of Resveratrol (3,5,4'-trihydroxy-trans-stilbene; Res) and has higher bioactivity than Res. To explore the mechanism of DNA damage induced by Pice in the presence of copper (Cu)(II), gel electrophoresis, UV-visible spectroscopy, fluorescence spectroscopy and Fourier transform infrared spectroscopy were used. The results of gel electrophoresis demonstrated that the hydroxyl radical played a critical role in DNA cleavage. Spectroscopy confirmed that the mechanism of DNA cleavage induced by Pice-Cu(II) involves the Haber Weiss and Fenton reactions. Pice chelates with Cu(II) as a bidentate ligand, and the Pice-Cu(II) complex undergoes intramolecular electron transfer to form the semiquinone radical anion and Cu(I), which may be reoxidated by O(2) to form Cu(II) with hydroxyl radical generation. In brief, the formation of the hydroxyl radical and the Cu(II)/Cu(I) redox cycle play a key role in inducing DNA damage. In this process, Pice demonstrated pro-oxidant properties. Oxidative product(s) of Pice, semiquinone, was formed and Cu(I) was reoxidized to Cu(II). The redox cycling of copper generated reactive oxygen species, which induced DNA cleavage, the hallmark of cell apoptosis. The mechanism of DNA breakage induced by Pice-Cu(II) may be a significant pathway through which cancer cells are killed.

Spectroscopy study on the interaction of quercetin with collagen.

In order to understand the interaction between quercetin and collagen clearly, the UV-vis, FTIR-HATR, and fluorescence spectroscopy were used, and the data obtained by these experiments suggested that quercetin could bind to collagen. Results of FTIR-HATR and UV-vis absorption spectra suggested that the interaction of quercetin and collagen did not alter the conformation of collagen. The fluorescence spectra revealed that collagen could cause the quenching of quercetin fluorescence through a dynamic quenching procedure. The calculated quenching constant K(SV) and bimolecular quenching rate constant k(q) suggested that diffusion played a major role in quenching. In addition, the interaction of quercetin and collagen was evaluated by calculating (determining) the number of binding sites (n) and apparent binding constant K(A).

[Measurement and analysis of nanometer particles of silica and carbon black by diffuse reflection FTIR spectra].

By using FTIR-FTS3000 spectrometer and infrared diffuse reflection accessory, the spectra of the nanometer particles of silica, carbon black and their blends with different weight ratio were collected and characterized. It was found from the measured results that blue-shift and broadening phenomenon occurred in the nanometer particle materials in comparison with the mass ones. These phenomena could be explained by the little size effect and quantum size effect. No perfect spectrum could be collected because of the strong absorbance of the nanometer particle materials. For the blends of silica and carbon black there was a maximum absorption corresponding to the critical concentration, where the weight ratio of silica to carbon black was 100 : 20, and below this ratio the relationship between the function F(R) and the concentration obeyed Lambert-Beer's law. Above this ratio, the absorbance will not increase with increasing the proportion of the carbon black in the system.

[Time resolved UV-Vis absorption spectra in synthetic process of quercetin complex with Al3+].

With a deuterium light source was used to provide the continuous light, the time resolved UV-Vis absorption spectra in the synthetic process of quercetin complex with Al3+ were measured by using an intensified ICCD spectroscopic detector. The measuing system was controlled synchronously by using a digital delay generator DG535. A total of 50 spectra with the exposure time of 1 micros for each spectrum and the time interval of 20 ms between two successional spectra were acquired. Results showed clearly that the typical bands centered at 254 and 374 nm of quercetin disappeared at 40 ms after the reaction started; at the same time, an absorption band centered at 384 nm of a transitional product appeared, and the typical absorption band centered at 300 nm of Al3+ still existed; with the reaction progressing, the bands of the transitional product and Al3+ disappeared, and the new bands centered at 267 and 436 nm of the complex of quercetin with Al3+ appeared and became stronger gradually; at 980 ms, the typical absorption band of Al3+ disappeared completely and the two typical absorption bands of the complex increased to the strongest. The synthetic reaction of quercetin complex with Al3+ finished within one second. The process of Al3+ being scavenged is shown in the spectra obviously. The prensent results provide experimental evidence for the Al3+ scavenging ability of quercetin.

[The measurement and analysis of visible-absorption spectrum and fluorescence spectrum of lycopene].

Using ICCD spectral detection system, the absorbency of lycopene-carbon bisulfide solution with different concentration was measured, and the result shows that in a specified range the absorption rule of lycopene solution agrees with Lambert-Beer Law. Absorption spectral wavelength shifts were measured respectively when lycopene was dissolved in acetone, normal hexane, petroleum ether, benzene, ethyl acetate, and carbon bisulfide, and comparing to acetone, different red-shift appeared when lycopene was dissolved in benzene, ethyl acetate, and carbon bisulfide when water was added in lycopene-acetone solution, t he absorbency of lycopene dropped, the fine structure of absorption spectrum became indistinct, and a new absorption peak appeared in UV. The reason for these phenomena is that the solvent molecule had different effect on lycopene molecule when lycopene was dissolved in different solvent. Using fluorecence spectrophotometer, fluorescence spectra of lycopene in different concentrations were collected, and the results show that the fluorescence spectra of lycopene were mainly in 500-680 nm. When concentration was lower than 50 microg x mL(-1), the fluorescence intensity linearly increased with increasing concentration, and when concentration was higher than 60 microg x mL(-1), the fluorescence intensity dropped because of the interaction between lycopene molecules.