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Quenched Sandwich-type Photoelectrochemical Aptasensor forProtein Detection based on Exciton Energy Transfer
摘要： This work proposes a quenched photoelectrochemical sensing method for highly selective and sensitive detection of protein via Energy Transfer (ET) effect between the AuNPs and CdS:Mn quantum dots. This detection was performed on a sandwich-type aptamer sensing interface. Chitosan modified CdS:Mn/TiO2/ITO electrode was used to immobilize capture DNA (S1) via -CONH- bond. In the presence of target protein, AuNPs labeled DNA (AuNPs-S2) was further bonded to the protein to fabricate sandwich sensing platform, which forced the AuNPs away from the electrode surface. In this state, the photocurrent was greatly depressed, mainly due to two factors: (a) the ET effect produced by interparticle distance between CdS:Mn and AuNPs; (b) the steric hindrance of AuNPs-S2 partly obstructs the diffusion of the electron donor. The photocurrent decreased with the increasing concentration of the target protein. Using thrombin as a target, this sensitized method showed a detectable range of 0.1 pM to 8 nM and a detection limit of 30 fM. It possessed high selectivity and good stability for detection of thrombin. This method is extremely flexible and can be extended to varieties of protein targets.
关键词： CdS:Mn,Photoelectrochemical aptasensor,Thrombin,Energy transfer,AuNPs
更新于2025-11-14 15:15:56
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Synthesis of color-tunable CdTe/CdS:Mn core-shell nanocrystal emitters
摘要： This study presents CdTe/CdS:Mn core–shell nanocrystals (NCs) prepared in aqueous media, using thioglycolic acid as capping agent. Firstly, CdTe NCs were synthesized, and then, Mn-doped CdS shell were deposited on the top of the CdTe core under Ar atmosphere. The NCs were structurally and optically characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), X-ray photoelectron (XPS), photoluminescence (PL), and Fourier transform infrared (FTIR) spectroscopy. The results obtained from XRD, XPS, PL, and EDX showed that the Mn ions were successfully introduced into the nanocrystalline shells. Moreover, the effect of Mn concentrations on the optical properties of the synthesized core-shell NCs was investigated. The effective band gap of the sample is in an indirect relationship with the Mn : Cd molar ratio, confirmed by PL analysis, and PL emissions can be measured at various wavelengths. The PL spectra showed 990 and 170 percent enhancement in the emission intensity of CdTe/CdS:Mn core/shell NCs (Mn: Cd 2.5%) compared to CdTe NCs and CdTe/CdS core/shell NCs, respectively. Consequently, the introduction of Mn dopants into the core-shell structures not only diminishes the density of quenching centers, but also reduces the effective band gap energies.
关键词： Core/Shell,Doping,Nanocrystals,CdTe/CdS:Mn,Luminescence
更新于2025-09-23 15:23:52
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Influence of the Cation on the Surface Electronic Band Structure and Magnetic Properties of Mn:ZnS and Mn:CdS Quantum Dot Thin Films
摘要： The effects of doping Mn into ZnS and CdS quantum dots are reported. Scanning tunneling spectroscopy spectra show a reduction in the electronic band gap in both CdS and ZnS upon incorporation of the Mn dopant. Mn:ZnS exhibits a rigid band shift toward higher bias which is reminiscent of a hole doping effect. This rigid band shift in Mn:ZnS is argued, with the help of X-ray photoelectron spectroscopy, to be due to a hole-doping mechanism caused by the favorable formation of Zn vacancies and a reduction in S vacancies compared to undoped ZnS films. In CdS no rigid band shift is observed even though the presence of Cd vacancies can be confirmed by photoemission and magnetic measurements. A strong sp-d hybridization is observed in the Mn:CdS film upon introducing the Mn dopant. d0 ferromagnetism is observed in both undoped ZnS and CdS quantum dot thin films at room temperature. Upon doping of Mn into ZnS the magnetization is reduced suggesting an antiparallel alignment of Mn-Mn or Mn-Zn vacancies nearest neighbors. Density Functional Theory supports the experimental results indicating the nearest neighbor Mn atoms prefer antiparallel alignment of their magnetic moments with preferred ground state of Mn in 3+ oxidation state.
关键词： CdS,Mn doping,quantum dots,magnetic properties,scanning tunneling spectroscopy,electronic band structure,X-ray photoelectron spectroscopy,density functional theory,ZnS
更新于2025-09-11 14:15:04