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Origin of Luminescence‐Based Detection of Metal Ions by Mn–Doped ZnS Quantum Dots
摘要： The health hazards associated with heavy metal ions in water demand the development of efficient and portable sensors, for rapid onsite detection of these ions. Several research groups have developed colorimetric/visual sensors based on plasmonic nanomaterials and quantum dots (QDs). Attempts for specific detection of metal ions have been partially achieved through the interaction between the metal ion and the passivating ligands around the QD. However, the underlying mechanism is not clearly understood. Here, we have used water-soluble Mn-doped ZnS QD to effectively detect Hg2 +, Pb2 +, and Cd2 + through the quenching of QD emission and understand the mechanism of sensing. Stern-Volmer plots indicate that the quenching is static in nature for Pb2 +, and Cd2 +, while for Hg2 +, it is a combination of static and dynamic quenching. Overall, the metal ions bind to the QD through the passivating ligand. After excitation, the electron from the conduction band of the QD can get injected to the metal ion – which decreases the photoluminescence of the QD. The electron injection depends on the reduction potential of the metal ion, the orbital overlap and the overall stabilization energy of the metal ions bound to the QD. Hence, this method of sensing is not selective to a specific metal ion. A solid state sensor of QD-rGO composite detects Pb2 + down to 0.4 ppb. The findings will be important for future improvement of colorimetric/visual sensors based on QD emission.
关键词： quantum dots,colorimetric sensing,Mn-doped ZnS,sensors
更新于2025-09-12 10:27:22
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Highly Responsive Ultraviolet Sensor Based on ZnS Quantum Dot Solid with Enhanced Photocurrent
摘要： Detection of visible blind UV radiation is not only interesting but also of technologically important. Herein, we demonstrate the efficient detection of UV radiation by using cluster like ZnS quantum dot solid nanostructures prepared by simple reflux condensation technique. The short-chain ligand 3-mercaptopropionic acid (MPA) involved in the synthesis lead to the cluster like formation of ZnS quantum dots into solids upon prolonged synthesis conditions. The ZnS QD solid formation resulted in the strong delocalization of electronic wave function between the neighboring quantum dots. It increases the photocurrent value, which can be further confirmed by the decrease in the average lifetime values from 64 to 4.6 ns upon ZnS cluster like QD solid formation from ZnS QDs. The ZnS quantum dot solid based UV sensor shows good photocurrent response and a maximum responsivity of 0.31 (A/W) at a wavelength of 390 nm, is not only competitive when compared with previous reports but also better than ZnS and metal oxide-based photodetectors. The device exhibits a high current value under low-intensity UV light source and an on/off ratio of IUV/Idark = 413 at zero biasing voltage with a fast response. Further, photocurrent device has been constructed using ZnS quantum dot solid nanostructures with graphene hybrids as an active layer to improve the enhancement of photoresponsivity.
关键词： graphene hybrids,ZnS quantum dot solid,photoresponsivity,UV sensor,photocurrent
更新于2025-09-12 10:27:22
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Metal-enhanced fluorescence of interlaminar composite film with self-assembled quantum Dots/Au@SiO2 microarchitecture
摘要： Quantum dots fluorescence-enhanced films, which mainly consisted of CdSe@ZnS quantum dots and noble metal nanoparticles or nanorods, were formed by layer-by-layer self-assembly techniques. This particular architecture consisting of metal nanoparticles-poly (diallyl dimethylammonium chloride) (PDDA)-QDs was characterized by those fabrication processes mainly including surface-modifying the oleic acid-capped CdSe@ZnS QDs ( high quantum yield of ~89% ) with mercaptopropionic acid (MPA) to be charged negatively (-COO-) for following solution-processed assembly, adjusting the size and coating the gold nanoparticles/nanorods with silica to form suitable dielectric insulation layer and further optimize the fluorescence-enhanced performance, as well as using the cationic polyelectrolyte to control the charges between layers and form opposite charges between two adjacent layers. After optimizing the structure of the quantum dot fluorescence-enhanced films and corresponding surface plasmon enhancement effect, the enhancement factor of 10.8 in Au NPs@SiO2-PDDA-QDs complex film and that of 24.7 in Au NRs@SiO2-PDDA-QDs complex film as compared with the pure quantum dot fluorescence film were achieved, respectively. This indicated that the Au NRs@SiO2-PDDA-QDs complex film was one of the most promising potentials for further display backlight and biometric identifier application.
关键词： CdSe@ZnS quantum dots,Au@SiO2 microarchitecture,electrostatic self-assembly,metal surface plasmon enhancement,Quantum dots fluorescence-enhanced films
更新于2025-09-12 10:27:22
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Glutathione Capped Core/shell CdSeS/ZnS Quantum Dots as a Medical Imaging tool for Cancer Cells
摘要： Nanomaterials have secured an enduring position as a promising contender for various biological applications. Quantum dot (QD) is one such example of nano sized semiconductor material having unique optical characteristics that makes it an ideal candidate to be used as imaging tool for today’s medical industry. In the present study, the L-Glutathione (L-GSH) capped L-GSH-CdSeS/ZnS core/shell QDs were applied to visualize MCF-7 human breast cancer cells. Time and dose dependent studies were done, to study the cell penetration and visualization of QDs within the cancer cells. MTT assay was done to derive the percent cell viability of cancer cells at different QDs dose concentrations. Cell cytotoxicity of the capped CdSeS/ZnS QDs were also studied on non-cancerous healthy cells. Human cancerous cells were treated with the selected doses of QDs for different time durations followed by counter staining of the cells with fluorescent DAPI nuclear stain to observe the reflected QD mediated effects. The small sized QDs were localized predominantly in the cytoplasm of MCF-7 cells and displayed no significant cytotoxicity on healthy cells. Our findings suggest that our new synthesized L-GSH-CdSeS/ZnS core/shell QDs could be highly biocompatible and can have a high probability of applications in bio-labeling and imaging for cancer diagnostics.
关键词： Diagnostics,CdSeS/ZnS Quantum dot,Toxicity,Biocompatible,Cancer,Cell death,MCF-7
更新于2025-09-12 10:27:22
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Electrochemiluminescence solid-state imprinted sensor based on graphene/CdTe@ZnS quantum dots as luminescent probes for low-cost ultrasensing of diethylstilbestrol
摘要： A novel molecularly imprinted electrochemiluminescence (MIP-ECL) sensor was fabricated for diethylstilbestrol (DES), which exploited the strategy of specific identification by molecularly imprinted polymers (MIPs) instead of expensive biomolecules. Core-shell quantum-dots (QDs) of CdTe@ZnS were utilized to enhance ECL emission. The sensor was assembled as a solid-state electrode by immobilizing CdTe@ZnS/reduced-graphene oxide (r-GO) composite on a glassy carbon electrode (GCE) surface, and then being covered with MIPs film with specific cavities. The fabricated sensor (denoted as MIP/CdTe@ZnS/r-GO/GCE) was based on the obstruction of ECL signals by DES molecules enriched on MIP film. The ECL intensity of the QDs-K2S2O8 system was reduced when the DES molecules were selectively rebound onto the MIP film by molecularly imprinted solid phase extraction (MISPE). Accordingly, the logarithm of the quenched ECL intensity versus the logarithm of the DES concentration was in a good linear relationship over a wide range from 1.8×10?3 to 25.0 nmol/L with the limit of detection (LOD) of 0.25 pmol/L (S/N = 3). The sensor also exhibits excellent selectivity with fast response and good accuracy. Lake water and milk samples were assayed by this sensor, and the recoveries ranging from 92.2% to 108.3% were obtained.
关键词： Solid-state electrode,Molecularly imprinted film,Diethylstilbestrol,CdTe@ZnS quantum-dots,Electrochemiluminescence sensor,Solid phase extraction
更新于2025-09-12 10:27:22
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F?rster Resonance Energy Transfer between Colloidal CuInS2/ZnS Quantum Dots and Dark Quenchers
摘要： F?rster resonance energy transfer (FRET) using colloidal semiconductor quantum dots (QDs) and dyes is of importance in a wide range of biological and biophysical studies. Here, we report a study on FRET between CuInS2/ZnS QDs and dark quencher dye molecules (IRDye QC-1). Oleate-capped QDs with photoluminescence quantum yields (PLQYs) of 55±4% are transferred into water by using two types of multifunctional polymer ligands combining imidazole groups and specific moieties with amine or methoxy groups as the terminal sites. The resulting water-dispersible QDs show PLQYs as high as 44±4% and exhibit long-term colloidal stability (at least 10 months at 4 °C in the dark) with a hydrodynamic diameter of less than 20 nm. A side-by-side comparison experiment was performed using the amine or methoxy-functionalized QDs for coupling to dark quencher dye molecules. The amine-functionalized QDs bind to the dye molecules via covalent bonds while methoxy-functionalized ones bind only weakly and non-specifically. The progressive quenching of the QD emission and shortening of its photoluminescence decay time upon increasing the number of conjugated dye molecules demonstrate that the QD acts as the energy donor and the dark quencher dye as the energy acceptor in a donor-acceptor FRET pair. The FRET dynamics of the QD-dye conjugates are simulated using two different models based on the possible origin of the multiexponential PL decay of the QDs (i.e., variations in nonradiative or radiative decay rates). The model based on the radiative decay rates provides a better fit of our experimental data and estimates a donor–acceptor distance (6.5 nm) that matches well the hydrodynamic radius of the amine-functionalized QDs.
关键词： dark quencher dye molecules,energy acceptor,multifunctional polymer ligands,CuInS2/ZnS,F?rster resonance energy transfer,colloidal semiconductor quantum dots,energy donor,photoluminescence quantum yields
更新于2025-09-12 10:27:22
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Synthesis of Colloidal Blue-Emitting InP/ZnS Core/Shell Quantum Dots with the Assistance of Copper Cations
摘要： Colloidal InP quantum dots (QDs) have been considered as one of the most promising candidates for the applications in display and bio-label due to intrinsic toxicity-free and high photoluminescence. On account of the uncontrollable nucleation and growth for the synthesis of InP, it remains a challenge to obtain high-quality blue-emitting InP QDs with uniform size distribution. Herein, we employ a novel synthetic approach for producing blue-emitting InP/ZnS core/shell QDs with the assistance of copper cations. The studies reveal that the copper ions could combine with phosphorus precursor to form hexagonal Cu3-xP nanocrystals, which competed with the nucleation process of InP QDs, resulting in the smaller sized InP QDs with blue photoluminescence emission. After the passivation of InP QDs with ZnS shell, the synthesized InP/ZnS core/shell QDs present bright blue emission (~425 nm) with photoluminescence quantum yield (PLQY) of ~25%, which is the shortest wavelength emission for InP QDs till now. This research provides a new way to synthesize ultra-small semiconductor nanocrystals.
关键词： InP/ZnS core/shell,blue-emitting,Colloidal InP quantum dots,photoluminescence quantum yield,copper cations
更新于2025-09-12 10:27:22
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Investigation of AgInS2/ZnS Quantum Dots by Magnetic Circular Dichroism Spectroscopy
摘要： Over recent years, quantum dots (QDs) based on ternary metal dichalcogenides have attracted a lot of attention due to their unique properties and a range of potential applications. Here, we review the latest studies on the optical properties of AgInS2/ZnS QDs with emphasis on their theoretical modeling, and present our investigations of electronic transitions invisible in unstructured absorption spectra of AgInS2/ZnS QDs. The analysis of the absorption, photoluminescence excitation (PLE), and magnetic circular dichroism (MCD) spectra of hydrophobic and hydrophilic AgInS2/ZnS QDs of different sizes enables us to determine positions of electron transitions in these QDs. We demonstrate that the use of the second derivative of PLE spectra provides more unequivocal data on the position of the energy transitions compared with the second derivative of absorption spectra. Analysis of the MCD spectra reveals that the magnetic field induces energy level mixing in AgInS2/ZnS QDs in contrast to the traditional Cd-based QDs, where MCD is associated only with removing degeneracy of the excited energy level.
关键词： AgInS2/ZnS,electronic transitions,magnetic circular dichroism,AIS,ternary quantum dots
更新于2025-09-12 10:27:22
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Strain Effects on the Band Gap and Diameter of CdSe Core and CdSe/ZnS Core/Shell Quantum Dots at Any Temperature
摘要： We present the results of an experimental study about strain effects on the core band gap and diameter of spherical bare CdSe core and CdSe/ZnS core/shell quantum dots (QDs) synthesized by using a colloidal technique at varying temperatures. Structural characterizations were made by using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) techniques. Optical characterizations were made by using UV-Vis absorption and fluorescence emission spectroscopies. The XRD analysis suggests that the synthesized bare CdSe core and CdSe/ZnS core/shell QDs have zinc blende crystal structure. HRTEM results indicate that the CdSe core and CdSe/ZnS QDs have average particle sizes about 3.50 nm and 4.84 nm, respectively. Furthermore, compressive strain causes an increase (decrease) in the core band gap (diameter) of spherical CdSe/ZnS core/shell QDs at any temperature. An elastic strain-modified effective mass approximation (EMA) predicts that there is a parabolic decrease (increase) in the core band gap (diameter) of QDs with temperature. The diameter of spherical bare CdSe core and CdSe/ZnS core/shell QDs calculated by using the strain-modified EMA, with core band gap extracted from absorption spectra, are in excellent agreement with the HRTEM data.
关键词： diameter,quantum dots,band gap,CdSe,strain effects,CdSe/ZnS,temperature
更新于2025-09-12 10:27:22
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Photoinduced Modulation of the Emission from СdSe/ZnS Quantum Dots by Photochromic Transformations of Diarylethenes
摘要： A spectral study of the interaction between the molecules of photochromic compounds of the diarylethene class and CdSe/ZnS quantum dots (QDs), in dependence of the structure and nature of functional substituents of photochromes, has been performed. It is shown that both chemical and physical interactions are accompanied by photoinduced modulation of QD emission as a result of photochromic transformations of diarylethenes caused by the inductive transfer of excitation energy from QDs to the diarylethene cyclic isomer.
关键词： diarylethenes,CdSe/ZnS quantum dots,nanomaterials,photoinduced modulation,photochromic transformations,ceramics
更新于2025-09-12 10:27:22