Flow‐injection chemiluminescence determination of haemoglobin in the blood

In this study, a sensitive and simple flow‐injection chemiluminescence (CL) method was developed for the quantitative analysis of haemoglobin. The method is based on the ability of haemoglobin to enhance the CL signal generated by a H₂O₂–K₄Fe(CN)₆–fluorescein alkaline system enhanced by CdTe quantum dots. Under the optimized conditions, haemoglobin can be detected in concentration range 7.35 × 10^–9–2.5 × 10^–6 mol/L, with a detection limit (3σ) of 1.8 × 10^–9 mol/L and a relative standard deviation (RSD; for 5 × 10^–7 mol/L haemoglobin) of 2.06% (n = 11). The present CL method was successfully applied for the determination of haemoglobin in three kinds of blood samples taken from an infant, an adult man, an adult woman and two reference samples. Compared with previous reports, the CL method described in this work is simple and rapid, with high sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly luminescent CdTe/CdS/ZnO core/shell/shell quantum dots fabricated using an aqueous strategy

To create core/shell/shell quantum dots (QDs) with high stability against a harmful chemical environment, CdTe/CdS QDs were coated with a ZnO shell in an aqueous solution. An interfaced CdS layer sandwiched between a CdTe core and ZnO shell provided relaxation of the strain at the core/shell interface since lattice parameters of CdS are intermediate between those of CdTe and ZnO. The photoluminescence (PL) peak wavelength of the core/shell/shell QDs was shifted from 569 to 615 nm by adjusting the size of CdTe cores and thickness of CdS and ZnO shells, along with the highest PL quantum yield of the core/shell/shell QDs reaching 80%, which implies promising applications in the field of biomedical labeling. Due to the decrease of surface defects, it was observed that PL lifetimes significantly increased at room temperature as follows: 29.6 34.2, and 47.5 ns for CdTe (537 nm), CdTe/CdS (555 nm) and CdTe/CdS/ZnO (581 nm) QDs, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly luminescent hybrid SiO2‐coated CdTe quantum dots: synthesis and properties

Novel hybrid SiO₂‐coated CdTe quantum dots (QDs) were created using CdTe QDs coated with a hybrid SiO₂ shell containing Cd²⁺ ions and a sulfur source via a sol–gel process in aqueous solution. Aqueous CdTe QDs with tunable emitting color created through a reaction between cadmium chloride and sodium hydrogen telluride was used as cores for the preparation of hybrid SiO₂‐coated CdTe QDs. In our experiments we found that the surface state of the cores and preparation conditions that affect the formation of the hybrid SiO₂ shell also greatly affect photoluminescence of the hybrid SiO₂‐coated CdTe QDs. The generation of CdS‐like clusters in the vicinity of the CdTe QDs, caused the quantum size effect of the QDs to be greatly reduced, which changes photoluminescence properties of the hybrid QDs fundamentally. Namely, the novel hybrid SiO₂ shell played an important role in generating a series of specific optical properties. In addition, the novel hybrid SiO₂ shell can be created if no CdTe QD is added. In order to gain an insight into the inter structure of the hybrid shell, we characterized the hybrid SiO₂‐coated CdTe QDs using X‐ray diffraction analysis and discuss the formation mechanism of such a hybrid structure. This work is significant because the novel hybrid SiO₂‐coated CdTe QDs with its excellent properties can be used in many applications, such as biolabeling and optoelectronic devices. Copyright © 2013 John Wiley & Sons, Ltd.     

Imaging of jasmonic acid binding sites in tissue

Hormones regulate the mechanism of plant growth and development, senescence, and plants’ adaptation to the environment; studies of the molecular mechanisms of plant hormone action are necessary for the understanding of these complex phenomena. However, there is no measurable signal for the hormone signal transduction process. We synthesized and applied a quantum dot-based fluorescent probe for the labeling of jasmonic acid (JA) binding sites in plants. This labeling probe was obtained by coupling mercaptoethylamine-modified CdTe quantum dots with JA using N-hydroxysuccinimide (NHS) as a coupling agent. The probe, CdTe–JA, was characterized by transmission electron microscopy, dynamic light scattering, and fluorescent spectrum and applied in labeling JA binding sites in tissue sections of mung bean seedlings and Arabidopsis thaliana root tips. Laser scanning confocal microscopy (LSCM) revealed that the probe selectively labeled JA receptor. The competition assays demonstrated that the CdTe–JA probe retained the original bioactivity of JA. An LSCM three-dimensional reconstruction experiment demonstrated excellent photostability of the probe.     

A sensitive fluorescent nanosensor for chloramphenicol based on molecularly imprinted polymer‐capped CdTe quantum dots

A novel fluorescent nanosensor using molecularly imprinted silica nanospheres embedded CdTe quantum dots (CdTe@SiO₂@MIP) was developed for detection and quantification of chloramphenicol (CAP). The imprinted sensor was prepared by synthesis of molecularly imprinting polymer (MIP) on the hydrophilic CdTe quantum dots via reverse microemulsion method using small amounts of solvents. The resulting CdTe@SiO₂@MIP nanoparticles were characterized by fluorescence, UV–vis absorption and FT‐IR spectroscopy and transmission electron microscopy. They preserved 48% of fluorescence quantum yield of the parent quantum dots. CAP remarkably quenched the fluorescence of prepared CdTe@SiO₂@MIP, probably via electron transfer mechanism. Under the optimal conditions, the relative fluorescence intensity of CdTe@SiO₂@MIP decreased with increasing CAP by a Stern–Volmer type equation in the concentration range of 40–500 µg L^–1. The corresponding detection limit was 5.0 µg L^–1. The intra‐day and inter‐day values for the precision of the proposed method were all <4%. The developed sensor had a good selectivity and was applied to determine CAP in spiked human and bovine serum and milk samples with satisfactory results. Copyright © 2015 John Wiley & Sons, Ltd.     

CdTe/ZnS quantum dots as fluorescent probes for ammonium determination

Novel CdTe/ZnS quantum dot (QD) probes based on the quenching effect were proposed for the simple, rapid, and specific determination of ammonium in aqueous solutions. The QDs were modified using 3‐mercaptopropionic acid, and the fluorescence responses of the CdTe/ZnS QD probes to ammonium were detected through regularity quenching. The quenching levels of the CdTe/ZnS QDs and ammonium concentration showed a good linear relationship between 4.0 × 10^?6 and 5.0 × 10^?4 mol/L; the detection limit was 3.0 × 10^?7 mol/L. Ammonium contents in synthetic explosion soil samples were measured to determine the practical applications of the QD probes and a probable quenching mechanism was described. Copyright © 2015 John Wiley & Sons, Ltd.     

Construction of photodynamic‐effect immunofluorescence probes by a complex of quantum dots,immunoglobulin G and chlorin e6 and their application in HepG2 cell killing

In this study, tri‐functional immunofluorescent probes (Ce6–IgG–QDs) based on covalent combinations of quantum dots (QDs), immunoglobulin G (IgG) and chlorin e6 (Ce6) were developed and their photodynamic ability to induce the death of cancer cells was demonstrated. Strategically, one type of second‐generation photosensitizer, Ce6, was first coupled with anti‐IgG antibody using the EDC/NHS cross‐linking method to construct the photosensitive immunoconjugate Ce6–IgG. Then, a complex of Ce6–IgG–QDs immunofluorescent probes was obtained in succession by covalently coupling Ce6–IgG to water soluble CdTe QDs. The as‐manufactured Ce6–IgG–QDs maintained the bio‐activities of both the antigen–antibody‐based tumour targeting effects of IgG and the photodynamic‐related anticancer activities of Ce6. By way of polyclonal antibody interaction with rabbit anti‐human epidermal growth factor receptor (anti‐EGFR antibody, N‐terminus), Ce6–IgG–QDs were labelled indirectly onto the surface of human hepatocarcinoma (HepG2) cells in cell recognition and killing experiments. The results indicated that the Ce6–IgG–QDs probes have excellent tumour cell selectivity and higher photosensitivity in photodynamic therapy (PDT) compared with Ce6 alone, due to their antibody‐based specific recognition and location of HepG2 cells and the photodynamic effects of Ce6 killed cells based on efficient fluorescence resonance energy transfer between QDs and Ce6. Copyright © 2015 John Wiley & Sons, Ltd.     

A simple FRET system using two‐color CdTe quantum dots assisted by cetyltrimethylammonium bromide and its application to Hg(II) detection

In this study, we developed a novel simple fluorescence resonance‐energy transfer (FRET) system between two‐color CdTe quantum dots (QDs) assisted by cetyltrimethylammonium bromide (CTAB). Mercaptopropionic (MPA)‐capped CdTe QDs serving as both donors and acceptors were successfully synthesized by changing the refluxing time in aqueous solution. CTAB micelles formed in water and minimized the distance between the donors and acceptors significantly by electrostatic interactions, improving FRET efficiency. Several factors that affected the fluorescence spectra of the FRET system were investigated. The prepared FRET system was feasible as an effective fluorescent probe to detect Hg(II) in aqueous solution. At pH 7.0, a linear relationship between the quenched fluorescence intensity of orange‐emitting acceptors (QDs_(A)) and Hg(II) concentration was acquired in the range 5–250 nmol/L with a detection limit of 1.95 nmol/L. The developed method showed excellent analytical performance for Hg(II) with high sensitivity and acceptable selectivity, reproducibility and stability. This finding indicated that the method has a promising potential application for environmental monitoring. This study demonstrated the great promise of QDs for expedient, low‐cost and high‐sensitivity detection of Hg(II).     

Sensitive detection of sodium cromoglycate with glutathione‐capped CdTe quantum dots as a novel fluorescence probe

A sensitive and simple analytical strategy for the detection of sodium cromoglycate (SCG) has been established based on a readily detectable fluorescence quenching effect of SCG for glutathione‐capped (GSH‐capped) CdTe quantum dots (QDs). The fluorescence of GSH‐capped CdTe QDs could be efficiently quenched by SCG through electron transfer from GSH‐capped CdTe QDs to SCG. Under optimum conditions, the response was linearly proportional to the concentration of SCG between 0.6419 and 100 µg/mL, with a correlation coefficient (R) of 0.9964; the detection limit (3δ/K) was 0.1926 µg/mL. The optimum conditions and the influence of coexisting foreign substances on the reaction were also investigated. The very effective and simple method reported here has been successfully applied to the determination of SCG in synthetic and real samples. It is believed that the established approach could have good prospects for application in the fields of clinical diseases diagnosis and treatment. Copyright © 2015 John Wiley & Sons, Ltd.     

Fluorescence quenching investigation on the interaction of glutathione‐CdTe/CdS quantum dots with sanguinarine and its analytical application

Water‐soluble glutathione (GSH)‐capped core/shell CdTe/CdS quantum dots (QDs) were synthesized. In pH 5.4 sodium phosphate buffer medium, the interaction between GSH‐CdTe/CdS QDs and sanguinarine (SA) was investigated by spectroscopic methods, including fluorescence spectroscopy and ultraviolet‐visible absorption spectroscopy. Addition of SA to GSH‐CdTe/CdS QDs results in fluorescence quenching of GSH‐CdTe/CdS QDs. Quenching intensity was in proportion to the concentration of SA in a certain range. Investigation of the quenching mechanism, proved that the fluorescence quenching of GSH‐CdTe/CdS QDs by SA is a result of electron transfer. Based on the quenching of the fluorescence of GSH‐CdTe/CdS QDs by SA, a novel, simple, rapid and specific method for SA determination was proposed. The detection limit for SA was 3.4 ng/mL and the quantitative determination range was 0.2–40.0 µg/mL with a correlation coefficient of 0.9988. The method has been applied to the determination of SA in synthetic samples and fresh urine samples of healthy human with satisfactory results. Copyright © 2013 John Wiley & Sons, Ltd.