析相微萃取-石墨炉原子吸收法测定地质样品中痕量金

以MIBK为络合剂和提取剂,乙醇为助溶剂,建立了析相微萃取-石墨炉原子吸收法测定地质样品中痕量金的分析方法。详细探讨了金的不同析相微萃取体系的特性及析相规律,优化了金-MIBK体系的最佳析相微萃取条件及石墨炉升温程序。所建立的方法线性范围为0.006~1.0μg/L,检出限为0.0013μg/L,相对标准偏差为1.5%(n=11),用于国家地质标准参考物质(GBW07289)的测定,分析结果与推荐值吻合。     

An ultrasensitive quantum dots fluorescent polarization immunoassay based on the antibody modified Au nanoparticles amplifying for the detection of adenosine triphosphate

In this work, an ultrasensitive fluorescent polarization immunoassay (FPIA) method based on the quantum dot/aptamer/antibody/gold nanoparticles ensemble has been developed for the detection of adenosine triphosphate (ATP). DNA hybridization is formed when ATP is present in the PBS solution containing the DNA-conjugated quantum dots (QDs) and antibody-AuNPs. The substantial sensitivity improvement of the antibody-AuNPs-enhanced method is mainly attributed to the slower rotation of fluorescent unit when QDs-labeled oligonucleotides hybridize with antibody modified the gold nanoparticle. As a result, the fluorescent polarization (FP) values of the system increase significantly. Under the optimal conditions, a linear response with ATP concentration is ranged from 8 × 10⁻¹² M to 2.40 × 10⁻⁴ M. The detection limit reached as low as 1.8 pM. The developed work provides a sensitive and selective immunoassay protocol for ATP detection, which could be applied in more bioanalytical systems.     

Preparation and Characterization of Polymer‐Protected Pt@Pt/Au Core‐Shell Nanoparticles

Poly(N‐vinyl‐2‐pyrolidone) protected Pt‐core bimetallic Pt/Au‐shell (Pt@Pt/Au) nanoparticles were prepared by multi‐step reduction of HAuCl₄ and H₂PtCl₆ alternately by hydrogen adsorbed on platinum atom. Transmission electronic microscopy (TEM) and x‐ray diffraction (XRD) were used to characterize Pt@Pt/Au nanoparticles. The structure of the shell of the nanoparticles seems to be the Au‐Pt solid solution.     

纳米金标记抗体增强SPR检测大肠杆菌O157∶H7

将金纳米粒子(AuNPs)标记的大肠杆菌O157∶H7(E.coli O157∶H7)的多克隆抗体(PAb)作为二抗,采用氨基偶联法将PAb固定在传感器表面作为一抗,通过三明治方法用双通道表面等离子体子共振(SPR)传感器对E.coli O157∶H7进行检测,并与SPR直接法检测进行了比较.结果表明,直接法的检出限为103cfu/mL,线性范围为103～109cfu/mL;AuNPs增强三明治法的检出限为10 cfu/mL,线性范围为10～1010cfu/mL,灵敏度比直接法提高了100倍,且具有更宽的检测范围.本方法不仅检测时间短,而且具有良好的选择性和重现性.     

纳米材料修饰电极上吸附态葡萄糖氧化酶的酶活性和电活性的比较

采用石英晶体微天平(QCM)技术, 监测了裸金(Au)电极、电沉积纳米金的金电极(Au_ed/Au)、多壁碳纳米管(MWCNTs)修饰的金电极(MWCNTs/Au)以及MWCNTs 修饰后再电沉积纳米金的金电极(Au_ed/MWCNTs/Au)上葡萄糖氧化酶(GOx)的吸附过程, 测算了吸附固定的GOx质量. 通过阳极恒电位检测吸附酶与葡萄糖发生酶反应所产生的过氧化氢, 考察了这些酶电极的安培响应, 并测算了各吸附态GOx的质量比生物活性(MSBAi).也通过循环伏安法研究酶的直接电化学, 测算了各吸附态GOx的电活性百分数(EAP_i). 实验结果表明, 酶吸附量和酶电极的安培响应满足MWCNTs/Au > Au_ed/MWCNTs/Au > Au_ed/Au > Au 的顺序; MSBA_i满足Au > Au_ed/MWCNTs/Au > Au_ed/Au > MWCNTs/Au的顺序; 而EAP_i则满足MWCNTs/Au > Au_ed/MWCNTs/Au > Au_ed /Au > Au的顺序. 根据酶和纳米材料的亲疏水作用以及酶的吸附量对实验结果进行了合理解释, 也定量验证了电极上吸附酶分子的总生物活性与酶电极的安培响应呈正相关关系, 所得数据和结论有助于纳米材料固定酶及其安培酶电极的研究.     

三角形Au@TiO2介孔催化剂可见光降解亚甲蓝

利用溶胶凝胶法制备出一种三角形Au@TiO₂核壳材料。经过水热晶化,该材料膨胀至300 nm,壳层TiO₂晶化为介孔锐钛矿相,但核心三角形Au颗粒的形貌保持不变。采用粉末X射线衍射(PXRD)、ζ电位、高分辨透射电子显微镜(HRTEM)、热重分析(TGA)、光致发光(PL)光谱、光电流(i-t)以及光催化降解技术,对样品的结构和性能进行了系统、详细的检测与分析。经过晶化处理的Au@TiO₂在可见光波段的光降解亚甲蓝性能比未晶化时有了显著的提升, 1 mg·mL^-1 Au@c-TiO₂可以在可见光照射1 h后实现对60 mg·L^-1亚甲蓝全降解。电子顺磁共振(EPR)测试表明·O₂^-和·OH两种自由基对光降解起到了很大作用。通过综合分析实验结果和时域有限差分(FDTD)分析,探究了催化反应的机理。     

A Au nanoparticle and polydopamine co-modified biosensor: A strategy for in situ and label-free surface plasmon resonance immunoassays

This article reports a surface plasmon resonance (SPR) strategy capable of label-free yet amplified in situ immunoassays for sensitive and specific detection of human IgG (hIgG), a serum marker that is important for the diagnosis of certain diseases. Primarily, a wavelength-modulated Kretschman configuration SPR analyzer was constructed, and Au film SPR biosensor chips were fabricated. Specifically, based on Au nanoparticles (AuNPs) adsorbed on the surface of the Au film, the AuNP/Au film was coated with polydopamine (PDA) to fix streptavidin (SA), and then the biotinylated antibodies were connected to the surface of the biosensor chip. The SPR analyzer was utilized for in situ real-time monitoring of hIgG. Due to the immunological recognition between the receptor and target, the surface plasmon waves produced by the attenuated total reflection were affected by the changes in the surface of the biosensor chip. The resonance wavelength (λ_R) of the output spectra gradually redshifted, and the redshift degrees were directly related to the target concentration. The biosensor can realize the in situ detection of hIgG, displaying satisfactory sensitivity, excellent specificity and stability. Briefly, by monitoring the shift in λ_R after specific binding, a new SPR immunoassay can be customized for label-free, in situ and amplified hIgG detection. The operating principle of this research could be extended as a common protocol for many other targets of interest.     

Abnormal adsorption behavior of dimethyl disulfide on gold surfaces

Adsorption of dimethyl disulfide (DMDS) on gold colloidal nanoparticle surfaces has been examined to check its binding mechanism. Differently from previous results, DMDS molecules adsorbed on the gold surface at high concentration showed the S–S stretching band at 500 cm⁻¹ in surface-enhanced Raman scattering (SERS) spectra, which indicates the presence of intact adsorption of DMDS molecules. However, it was found that the S–S bond of disulfides was easily cleaved on the gold surface at low concentration. These behaviors were not observed for diethyl disulfide (DEDS) or diphenyl disulfide (DPDS). Our results indicate that DMDS molecules with the shortest alkyl chains on the gold surface can be inserted into self-assembled monolayers (SAMs) without the S–S bond cleavage during self-assembly due to insufficient lateral van der Waals interaction and the low adsorption activity of disulfides, whereas DEDS with longer alkyl chains or DPDS with the weak disulfide bond dissociation energy would not. These unusual DMDS adsorption behaviors were examined by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). We also compared the bonding dissociation energy of the S–S bonds of various disulfides by means of a density functional theory (DFT) calculation.