A visual electrochemiluminescence biosensor based on CuInZnS quantum dots for superoxide dismutase detection.

Superoxide dismutase (SOD), also known as liver protein, is a substance widely distributed in various biological cells. It has the function of catalyzing the disproportionation reaction of superoxide free radicals. SOD can form an antioxidant chain together with peroxidase, catalase, and other substances in the body of organisms, and thus, is one of the indispensable important substances in the body of organisms. In this work, we provided a simple and fast visual electrochemiluminescence (ECL) sensor for SOD detection. CuInZnS quantum dots (QDs) worked as the ECL luminophore with hydrogen peroxide as co-reactant. In the sensing process, SOD and CuInZnS QDs on a glassy carbon electrode (GCE) competed with each other for hydrogen peroxide to produce superoxide during electrochemical luminescence, thus quenching the ECL signal of CuInZnS QDs. The proposed sensor can quantify SOD with a limit of detection (LOD) of 0.03 µg/mL. In addition, the change in the CuInZnS QDs ECL signal was easily observed with a smartphone camera. The results indicated that this sensor could effectively work in the detection of SOD in human blood. Graphical abstract.

A novel detection method of human serum albumin based on CuInZnS quantum dots-Co2+ sensing system.

We developed a novel "turn off-on" sensor for human serum albumin (HSA) detection based on CuInZnS quantum dots (CIZS QDs). The photoluminescence (PL) of QDs can be "turned off" by Co(II) first. Because of the strong binding ability of HSA with Co2+, Co2+ can be removed from CIZS QDs with the addition of HSA. As a result, the PL of CIZS QDs probe can be "turned on" with an increased concentration of HSA over a wide range. The analyte HSA concentration had a proportional linear relationship with the recovered PL intensity of CIZS QDs. The detection limit for HSA was 4.5 × 10-8 mol L-1. The results indicated that the CIZS QDs- Co2+-BSA sensing system possessed higher sensitivity and better practicability for HSA detection.

Ligand-assisted structure tailoring of highly luminescent Cu-In-Zn-S/ZnS//ZnS quantum dots for bright and stable light-emitting diodes.

Harnessing environment-friendly and low-cost multinary Cu-In-Zn-S quantum dots (QDs) as emitters for light-emitting diodes (LEDs) has attracted great attention for display and lighting application. However, suboptimal QD structure is a huge obstacle, which results in serious non-radiative recombination and efficiency roll-off. Herein, we synthesized structure-tailored Cu-In-Zn-S/ZnS//ZnS QDs by improving the reactivity of shell growth by 2-ethylhexanoic acid (EHA) ligands. The EHA-assisted shell growth can boost an extended alloyed layer at the core-shell interface and a smoothed confinement barrier, which effectively passivate the interface defects and suppress Förster resonance energy transfer (FRET) process. These synthesized QDs display a bright photoluminescence emission (quantum yield of 83%) and a larger size of 8.4 nm. Moreover, the resulting LEDs based on the EHA-assisted QDs exhibit a maximum luminance of 8074 cd/m2, and a current efficiency of 7.3 cd/A with a low efficiency roll-off. Our results highlight a remarkable ligand strategy to tailor the QD structure for high performance QD-based LEDs.

Pb2+ Responsive Cu-In-Zn-S Quantum Dots With Low Cytotoxicity.

Water-soluble Cu-In-Zn-S quantum dots (CIZS QDs) with orange fluorescence have been synthesized with a glutathione (GSH) as stabilizer via facile a one-step hydrothermal method. The optimal reaction conditions of CIZS QDs including temperature, time, pH, and the molar ratios of precursors were studied. TEM results indicate that the aqueous-dispersible CIZS QDs are quasi-spherical, and the average diameters are 3.76 nm with excellent fluorescent stability. Furthermore, the cytotoxicity of CIZS QDs was investigated by the microcalorimetry combining with TEM and the IC 50 was 10.2 µM . CIZS QDs showed a promising perspective in applications such as a fluorescent probe for bioimaging and biolabeling due to the low cytotoxicity and good biocompatibility. Moreover, the CIZS QDs can distinguish Pb2+ ion from other ions, offering great potentials in lead ion determination in drinking water. According to the results of UV, XRD, FL, PL, and ITC methods, the mechanism of CIZS QDs-Pb2+ assay is due to hydrogen bonding or van der Waals forces in the formation of Pb2+ and CIZS QDs.

Determination of ascorbic acid and ascorbate oxidase based on quaternary CuInZnS QDs/thiochrome ratiometric fluorescence sensing system.

In this work, a rapid and sensitive ratiometric fluorescence sensing method for the detection of ascorbic acid (AA) and ascorbate oxidase (AA-Ox) was developed. MPA capped quaternary CuInZnS QDs with fluorescence emission wavelength of 580 nm was synthesized by hydrothermal synthesis. Thiamine (VB1) can be oxidized by KMnO4 to yield thiochrome (oxVB1) with a fluorescence emission peak at 459 nm. So positively charged thiamine and negatively charged MPA modified CuInZnS QDs can form a ratiometric fluorescence system via electrostatic interaction. The presence of AA will consume KMnO4, which can inhibit the oxidization of thiamine, accompanied with a decrease of the fluorescence intensity at 459 nm, while the fluorescence of CuInZnS QDs at 580 nm remains the same when AA is present, so the fluorescence intensity ratio (I459/I580) decreased. When AA was oxidized by AA-Ox, KMnO4 could not be reduced by AA, which caused the fluorescence intensity of thiochrome at 459 nm restored, and the fluorescence intensity ratio (I459/I580) increased again. Therefore, AA and AA-Ox can be monitored by detecting the fluorescence intensities ratio at 459 and 580 nm. Moreover, the developed detection system for AA and AA-Ox displayed a good linear relationship from 0.05 to 0.25 µmol L-1 and 0.1-5 mU·mL-1, and the detection limit are 0.011 µmol L-1 and 0.078 mU·mL-1, respectively. The proposed method was applied to the determination of AA-Ox in human serum samples with satisfactory results.

A novel amplified electrochemiluminescence biosensor based on Au NPs@PDA@CuInZnS QDs nanocomposites for ultrasensitive detection of p53 gene.

In this work, a novel surface plasmon resonance (SPR) enhanced electrochemiluminescence (ECL) biosensing model was first designed based on Au NPs@polydopamine (PDA)@CuInZnS QDs nanocomposite. Au NPs were coated with the PDA layer via the electrostatic force. CuInZnS QDs were bound on the surface of Au NPs@PDA nanocomposite. CuInZnS QDs worked as ECL luminophore in the sensing application. PDA shell not only controlled the separation length between Au NPs and QDs to induce SPR enhanced ECL response, but also limited the potential charge transfer and ECL quenching effect. As a result, the nanocomposite ECL intensity was twice that of QDs with K2S2O8. The tumor suppressor p53 gene was detected in the amplified ECL sensing system. The sensing method has a linear response in the range of 0.1 nmol/L to 15 nmol/L with a detection limit of 0.03 nmol/L. The DNA biosensor based on the nanocomposite showed excellent sensitivity, selectivity, reproducibility and stability and was applied in spiked human serum samples with satisfactory results.

Synthesis of Cu-Deficient and Zn-Graded Cu-In-Zn-S Quantum Dots and Hybrid Inorganic-Organic Nanophosphor Composite for White Light Emission.

Cu-deficient graded-zinc Cu-In-Zn-S (CIZS) quantum dots (QDs) were synthesized by a two-step solvothermal method. These CIZS QDs exhibited size and composition tunable photoluminescence characteristics with emission color tunable from greenish-yellow to orange to red with a relatively high quantum yield between 45 and 60%. Novel white-light-emitting (WLE) hybrid composite is fabricated by integrating the blue-emissive 1,4-bis-2-(5-phenyl oxazolyl)-benzene (POPOP) organic fluorophore and quaternary CIZS inorganic QDs. Integrating CIZS QDs with POPOP fluorophore resulted in series of tunable emission colors with CIE coordinates lying in a straight line between the coordinates of the end member. WLE was shown for hybrid mixture comprising 0.5 nM of POPOP and 3 mg/mL of CIZS QDs with color coordinates (0.3312, 0.3324). Thin films of this hybrid mixture in PMMA matrix coated on UV-LED or on glass substrates with UV backlit light also showed broadband WLE with ideal CIE color coordinates of (0.34, 0.33), high color-rendering index value of 92, and correlated color temperature value of 5143 K. The hybrid composite exhibit Forster resonance energy transfer cascading from POPOP to CIZS which results in emission covering the entire visible spectral range. POPOP and CIZS QDs hybrid composite is a versatile material for WLED applications.