Synthesis of highly fluorescent glutathione-capped ZnxHg1−xSe quantum dot and its application for sensing copper ion

Highly selective visual sensing of copper based on fluorescence enhanced glutathione-Au nanoclusters

A blue emission glutathione stabilized Au nanoclusters prepared by an Au/Histidine complex with ligand-exchanges method was used for sensing of copper ions. We found that the glutathione stabilized Au NCs which has fluorescence emission hundred times higher than the Au/Histidine complex and has a highly selective fluorescence quenching response to copper ion. Other common metal ions, such as mercury, lead, iron and zinc, which could obviously quench or enhance the fluorescence of Au/Histidine complex, do not interfere the sensing of copper using glutathione stabilized Au nanocluster. The possible quenching mechanism and the dynamic quenching process for copper detection were also discussed. The results indicated that copper in the range from 0.5 to 300.0μM could be linearly detected and the detection could be finished quickly in 5min. A visual detection method for copper ion that may be used to fast warn copper pollution in waters by naked eyes observation was also be developed using the glutathione stabilized Au NCs probe.

High Sensitivity Detection of Copper Ions in Oysters Based on the Fluorescence Property of Cadmium Selenide Quantum Dots

Cadmium selenide (CdSe) quantum dots (QDs) were synthesized by water phase synthesis method using 3-mercaptopropionic acid (3-MPA) as a stabilizer, and they were applied to the detection of copper ions (Cu2+). The results showed that CdSe QDs have excellent selectivity and sensitivity toward Cu2+. The fluorescence intensity of CdSe QDs decreased with the increase of Cu2+ concentration. The linear range was from 30 nM to 3 μM, and the detection limit was 30 nM. Furthermore, CdSe QDs were used for detecting the concentration of Cu2+ in oysters. The content of Cu2+ was 40.91 mg/kg, which was close to the one measured via flame atomic absorption spectrometry (FAAS), and the relative error was 1.81%. Therefore, CdSe QDs have a wide application prospect in the rapid detection of copper ions in food.

A “turn-off” fluorescent sensor for the selective and sensitive detection of copper(ii) ions using lysozyme stabilized gold nanoclusters

In this contribution, we have developed a simple, environmentally friendly fluorescent turn-off sensor for the detection of copper (Cu²⁺) ions in aqueous solution by using lysozyme stabilized gold nanoclusters (Lys-AuNCs) as a fluorescent probe.

Colloidal semiconductor nanocrystals: the aqueous approach

This article summarizes the main achievements and challenges in the field of the aqueous synthesis of semiconductor quantum dots in colloidal solutions. Developments in the last two decades demonstrate the great potential of this approach to synthesize nanocrystalline materials with superior properties such as strong photoluminescence, long time stability and compatibility with biological media, and the variability in assembling and self-assembling into larger structures or on surfaces. Being relatively straightforward, the aqueous approach provides some advantages such as versatility, scalability, environmental friendliness and cost effectiveness, leading in summary to very attractive application perspectives.

A novel phosphorescence sensor for Co2+ ion based on Mn-doped ZnS quantum dots

N-acetyl-L-cysteine-capped Mn-doped ZnS quantum dots (QDs) were prepared by hydrothermal methods. It could emit phosphorescence at 583 nm with the excitation wavelength at 315 nm. The phosphorescence intensity of QDs could be quenched dramatically by increasing the concentration of Co(2+) ion. The novel phosphorescence sensor based on N-acetyl-L-cysteine-capped QDs was developed for detecting Co(2+) ion with a linear dynamic range of 1.25 × 10(-6) -3.25 × 10(-5) m. The limit of detection and RSD were 6.0 × 10(-8) m and 2.3%, respectively. Interference experiments showed excellent selectivity over numerous cations such as alkali, alkaline earth and transitional metal ions. The possible quenching mechanism was also examined by phosphorescence decays. The proposed phosphorescence method was further applied to the trace determination of Co(2+) ion in tap and pond water samples with recoveries of 97.75-103.32%.

Nanoparticles for Improving Cancer Diagnosis

Despite the progress in developing new therapeutic modalities, cancer remains one of the leading diseases causing human mortality. This is mainly attributed to the inability to diagnose tumors in their early stage. By the time the tumor is confirmed, the cancer may have already metastasized, thereby making therapies challenging or even impossible. It is therefore crucial to develop new or to improve existing diagnostic tools to enable diagnosis of cancer in its early or even pre-syndrome stage. The emergence of nanotechnology has provided such a possibility. Unique physical and physiochemical properties allow nanoparticles to be utilized as tags with excellent sensitivity. When coupled with the appropriate targeting molecules, nanoparticle-based probes can interact with a biological system and sense biological changes on the molecular level with unprecedented accuracy. In the past several years, much progress has been made in applying nanotechnology to clinical imaging and diagnostics, and interdisciplinary efforts have made an impact on clinical cancer management. This article aims to review the progress in this exciting area with emphases on the preparation and engineering techniques that have been developed to assemble "smart" nanoprobes.

Dual-emitting nanocomposites derived from rare-earth compound nanotubes for ratiometric fluorescence sensing applications

A new class of ratiometric fluorescence sensors composed of rare-earth (RE) compound nanotubes is described. Polyethylenimine-coated yttrium hydroxide fluoride nanotubes (YHF NTs) that were synthesized hydrothermally exhibit highly efficient fluorescence when doped with RE ions. The polyethylenimine on the NTs facilitates the incorporation of phosphors such as quantum dots or organic dyes onto the NT surface to produce dual-emitting nanocomposites which are excellent ratiometric fluorescence sensors. The phosphor layer and underlying tubes in the nanocomposites act as the indicator and reference probes, respectively. This ratiometric fluorescence method which can be applied to the detection of heavy metals in solutions, temperature sensing, and pH sensing boasts high sensitivity and selectivity as well as better accuracy than traditional intensity-based fluorescence methods.

Composition-tunable alloyed semiconductor nanocrystals

The ability to engineer the band gap energy of semiconductor nanocrystals has led to the development of nanomaterials with many new exciting properties and applications. Band gap engineering has thus proven to be an effective tool in the design of new nanocrystal-based semiconductor devices. As reported in numerous publications over the last three decades, tuning the size of nanocrystalline semiconductors is one way of adjusting the band gap energy. On the other hand, research on band gap engineering via control of nanocrystal composition, which is achieved by adjusting the constituent stoichiometries of alloyed semiconductors, is still in its infancy. In this Account, we summarize recent research on colloidal alloyed semiconductor nanocrystals that exhibit novel composition-tunable properties. Alloying of two semiconductors at the nanometer scale produces materials that display properties distinct not only from the properties of their bulk counterparts but also from those of their parent semiconductors. As a result, alloyed nanocrystals possess additional properties that are composition-dependent aside from the properties that emerge due to quantum confinement effects. For example, although the size-dependent emission wavelength of the widely studied CdSe nanocrystals can be continuously tuned to cover almost the entire visible spectrum, the near-infrared (NIR) region is far outside its spectral range. By contrast, certain alloy compositions of nanocrystalline CdSe(x)Te(1-x), an alloy of CdSe and CdTe, can efficiently emit light in the NIR spectral window. These NIR-emitting nanocrystals are potentially useful in several biomedical applications. In addition, highly stable nanocrystals formed by alloying CdSe with ZnSe (i.e., Zn(x)Cd(1-x)Se) emit blue light with excellent efficiency, a property seldom achieved by the parent binary systems. As a result, these materials can be used in short-wavelength optoelectronic devices. In the future, we foresee new discoveries related to these interesting nanoalloys. In particular, colloidal semiconductor nanoalloys that exhibit composition-dependent magnetic properties have yet to be reported. Further studies of the alloying mechanism are also needed to develop improved synthetic strategies for the preparation of these alloyed nanomaterials.