A phenol phosphorescent microsensor of mesoporous molecularly imprinted polymers

Based on the optical quenching phenomenon, a smart mesoporous phosphorescent microsensor was built. It is a phenol microsensor, which inherits a high selectivity of molecularly imprinted polymers (MIPs) and room-temperature phosphorescence (RTP) properties of Mn-doped ZnS quantum dots (QDs). On the surface of silane-modified Mn-doped ZnS QDs, the phenol microsensor was synthesized by a sol–gel process. Because of the presence of a porogenic agent, a mesoporous structure played an important role in increasing the detection sensitivity. The MPTS-modified Mn-doped ZnS QDs were used as solid supports and auxiliary monomers. Under optimal conditions, the experiment for the detection of phenol had a linear range of 5.0 to 50 μmol L⁻¹ with a correlation coefficient of 0.9983 and a high imprinting factor (IF) of 3.28. In addition, the as-prepared Mn-doped ZnS QD@ms-MIPs were successfully applied for phenol determination and selectivity in water samples. Therefore, this study provides a highly selective and sensitive mesoporous phosphorescent microsensor for the detection of phenol.

Based on the optical quenching phenomenon, a smart mesoporous phosphorescent microsensor was built.     

A label-free RTP sensor based on aptamer/quantum dot nanocomposites for cytochrome c detection

Given the outstanding room-temperature phosphorescence (RTP) of Mn–ZnS quantum dots (QDs) and the specific recognition performance of the aptamer, we built phosphorescent composites from aptamers conjugated with polyethyleneimine quantum dots (PEI-QDs) and applied them to cytochrome c (Cyt c) detection. Specifically, QDs/CBA composites were generated from the electrostatic interaction between the positively-charged PEI-QDs and the negatively-charged Cyt c binding aptamer (CBA). With the presence of Cyt c, the Cyt c can specifically bind with the QDs/CBA composites, and quench the RTP of QDs through photoinduced electron-transfer (PIET). Thereby, an optical biosensor for Cyt c detection was built, which had a detection range of 0.166–9.96 μM and a detection limit of 0.084 μM. This aptamer-mediated phosphorescent sensor with high specificity and operational simplicity can effectively avoid the interference of scattering light from complex substrates. Our findings offer a new clue for building biosensors based on QDs and aptamers.

In this study, the nanocomposites from polyethyleneimine-capped Mn-doped ZnS QDs (PEI-QDs) and Cyt c binding aptamer (CBA) were prepared and used as Cyt c RTP sensors..     

“Turn on” room-temperature phosphorescent biosensors for detection of hyaluronic acid based on manganese-doped ZnS quantum dots

Biosensors based on excellent optical properties of quantum dots (QDs) nanohybrids are efficient for biological detection. In this work, a room-temperature phosphorescent (RTP) PDAD–Mn–ZnS QDs biosensor was constructed with poly(diallyldimethylammonium chloride) (PDAD) as the modifier of MPA-capped Mn–ZnS QDs, and used to detect hyaluronic acid (HA). The newly-added HA induced severe electrostatic interaction with PDAD–Mn–ZnS QDs, leading to the aggregation between PDAD–Mn–ZnS QDs and HA and thereby enhancing RTP. The enhancement of RTP was proportional to the HA concentrations within certain ranges. On this basis, a high-performance HA sensor was built and this sensor had a detection limit of 0.03 μg mL⁻¹ and a detection range of 0.08–2.8 μg mL⁻¹. This proposed RTP sensor can avoid interferences from the background fluorescence or scattering light of the matrix that are encountered in spectrofluorometry. Thus, this biosensor is potentially suitable for detection of HA in real samples without complicated pretreatment.

Fabricating PDAD–Mn–ZnS QDs nanohybrids as a facile room-temperature phosphorescent biosensor for detection of hyaluronic acid.     

Molecularly imprinted polymer coated Mn-doped ZnS quantum dots embedded in a metal–organic framework as a probe for selective room temperature phosphorescence detection of chlorpyrifos

As one of the most widely used organophosphorus pesticides, chlorpyrifos (CPF) is toxic to humans. However, the rapid, effective and sensitive detection of CPF is still a challenge. In this paper, a novel molecularly imprinted phosphorescent sensor with a core–shell structure (Mn:ZnS QDs@ZIF-8@MIP) using Mn:ZnS quantum dots (QDs) as phosphorescent emitters was prepared for the highly sensitive and selective detection of CPF, and a simple and rapid room-temperature phosphorescence (RTP) detection method for CPF was proposed. For the prepared Mn:ZnS QDs@ZIF-8@MIP, Mn:ZnS QDs had good phosphorescence emission characteristics, ZIF-8 as support materials was used to improve the dispersibility of Mn:ZnS QDs, and molecularly imprinted polymer (MIP) on the surface of ZIF-8 was used to improve the selectivity of Mn:ZnS QDs for CPF. Under the optimal response conditions, the RTP intensity of Mn:ZnS QDs@ZIF-8@MIP showed a rapid response to CPF (less than 5 min), the RTP intensity ratio of P₀/P had a good linear relationship with the concentration of CPF in the range of 0–80 μM, and the detection limit of this method was 0.89 μM with the correlation coefficient of 0.99. Moreover, this simple and rapid method has been successfully used to detect CPF in real water samples with satisfactory results, and the recoveries ranged from 92% to 105% with a relative standard deviation of less than 1%. This method combines the advantages of phosphorescence emission and molecular imprinting, and greatly reduces the potential interferences of competitive substances, background fluorescence and scattered light, which opens up a broad prospect for the highly sensitive and selective detection of pollutants in water based on molecularly imprinted phosphorescent sensors.

As one of the most widely used organophosphorus pesticides, chlorpyrifos (CPF) is toxic to humans, and Mn:ZnS QDs@ZIF-8@MIP are prepared for the highly sensitive and selective detection of CPF.     

Preparation of DNA functional phosphorescent quantum dots and application in melamine detection in milk

Bio-functionalization of quantum dots (QDs) is of important value in practical applications. With single-stranded DNA (ssDNA) rich in thymine T and thioguanine G taken as the template, a new-type nanocomposite material (ssDNA-PQDs) synthesized from low-toxicity T-ssDNA functionalized Mn–ZnS and room-temperature phosphorescent (RTP) QDs (PQDs) was prepared in this paper by optimizing synthesis conditions, and these ssDNA-PQDs could emit orange RTP signals at 590 nm. As these ssDNA-PQDs are rich in T sequences and T sequences can bond with melamine through the hydrogen-bond interaction, ssDNA-PQDs experience aggregation, thus causing phosphorescent exciton energy transfer (PEET) between ssDNA-PQDs of different particle sizes and their RTP quenching. Based on this principle, an RTP detection method for melamine was established. The linear range and detection limit of the detection method are 0.005–6 mM and 0.0016 mM respectively. As this method is based on the RTP nature of ssDNA-PQDs, it can avoid disturbance from background fluorescence and scattered light of the biological fluid, and it is very suitable for melamine detection in the biological fluid milk.

Preparation of phosphorescent quantum dots taking single-stranded DNA as a template and their application to melamine detection in milk.     

Mixture of quantum dots and ZnS nanoparticles as emissive layer for improved quantum dots light emitting diodes

Recently, quantum dots based light-emitting diodes (QLEDs) have received huge attention due to the properties of quantum dots (QDs), such as high photoluminescence quantum yield (PLQY) and narrow emission. To improve the performance of QLEDs, reducing non-radiative energy transfer is critical. So far, most conventional methods required additional chemical treatment like giant shell and/or ligands exchange. However that triggers unsought shifted emission or reduced PLQY of QDs. In this work, we have firstly suggested a novel approach to improve the efficiency of QLEDs by introducing inorganic nanoparticles (NPs) spacer between QDs, without additional chemical treatment. As ZnS NPs formed a mixture layer with QDs, the energy transfer was reduced and the distance between the QDs increased, leading to improved PLQY of mixture layer. As a result, current efficiency (CE) of the QLED device was improved by twice compared with one using only QDs layer. This is an early report on utilizing ZnS NPs as an efficient spacer, which can be utilized to other compositions of QDs.

Mixture of quantum dots and ZnS nanoparticles as emissive layer for improved QLEDs by decreasing energy transfer between the QDs.     

Highly sensitive and selective detection of naproxen via molecularly imprinted carbon dots as a fluorescent sensor

The overuse and inappropriate discharge of naproxen, a common anti-inflammatory medication and an emerging contaminant in water, is detrimental to human health and bodies of water. Here, we design a fluorescent sensor based on molecularly imprinted carbon dots (CDs) for highly selective detection of trace amounts of naproxen. The CDs were encapsulated into the pores of silica through a sol–gel based method and provide fluorescent signal. After removal of the template molecules, a molecularly imprinted polymer layer was formed and the fluorescence of the CDs sensor was selectively quenched by naproxen. A detection limit of as low as 0.03 μM and a linear range of 0.05–4 μM for detecting naproxen in aqueous solution were obtained. High recoveries of naproxen levels in waste water and urine samples for practical application were also achieved. In addition, the accurate detection performance of sensor was maintained during the UV degradation of naproxen.

A highly selective fluorescent sensor for naproxen utilizes carbon dots as the fluorophore and molecularly imprinted polymer to provide the recognition sites. The fluorescence of carbon dots can be selectively quenched by naproxen.     

Hydrothermal synthesis of water-soluble Mn- and Cu-doped CdSe quantum dots with multi-shell structures and their photoluminescence properties

Optical properties of semiconductor quantum dots (QDs) can be tuned by doping with transition metal ions. In this study, water-soluble CdSe/ZnS:Mn/ZnS QDs with the core/shell/shell structure were synthesized through a hydrothermal method, in which the surface of the CdSe core was coated with a ZnS:Mn shell and ZnS capping shell. Herein, the CdSe core QDs were prepared first and then doped with Mn²⁺; therefore, the QD size and doping level could be controlled independently and interference from the self-purifying effect could be avoided. When CdSe cores with diameters less than 1.9 nm were used, Mn-related photoluminescence (PL) was observed as the main PL band, whereas the band-edge PL was mainly observed when larger CdSe cores were used. Furthermore, using ZnS:Cu as the doping shell layer, CdSe/ZnS:Cu/ZnS and ZnSe/ZnS:Cu/ZnS nanoparticles were successfully synthesized, and Cu-related PL was clearly observed. These results indicate that the core/shell/shell QD structure with doping in the shell layer is a versatile method for synthesizing doped QDs.

The core/shell/shell QD structure with doping in the shell layer is a versatile method for synthesizing doped QDs.     

PEGylation of protein-imprinted nanocomposites sandwiching CdTe quantum dots with enhanced fluorescence sensing selectivity

Fluorescent sensors combining the selective recognition of protein molecularly imprinted polymers (MIPs) and the fluorescent sensing of quantum dots (QDs) have been studied considerably, but their fluorescence sensing selectivity for the target proteins remains to be increased. Herein, we propose a strategy for increasing the sensing selectivity by post-imprinting PEGylation of surface protein-imprinted nanocomposites with embedded QDs. With bovine hemoglobin (BHb) as a model protein template, protein MIP nanolayers were anchored over the CdTe QD decorated SiO₂ nanoparticles by the sol–gel process using aminopropyltriethoxy silane and tetraethoxysilicane. PEG chains were then grafted onto the surface of the imprinted nanostructures via the nucleophilic reaction of the surface amine groups with N-hydroxysuccinimide ester-terminal methoxy-PEG, followed by template removal. The resultant PEGylated sensors showed significantly improved aqueous dispersion stability compared with the non-PEGylated controls. More importantly, such PEGylation greatly increased the fluorescence response selectivity, with the Stern–Volmer equation based imprinting factor increasing from 2.7 to 5.4. The PEGylated sensors were applied to determine BHb in bovine serum samples with satisfactory recoveries at three spiking levels ranging from 94.3 to 103.7%, indicating their potential application in real samples.

PEGylated CdTe quantum dots containing protein-imprinted nanocomposites showing enhanced fluorescence sensing selectivity.     

Enhanced light emission of quantum dot films by scattering of poly(zinc methacrylate) coating CdZnSeS/ZnS quantum dots and high refractive index BaTiO3 nanoparticles

Quantum dots (QDs) have received considerable attention in information displays owing to their high quantum yield, high colour purity and low-cost fabrication. However, light emission for ultra-thin QD films with low mass percentage of QDs still need to be improved because the blue light can directly transmit the films, leading to insufficient energy to excite the QDs. In this study, we report QD films based on a poly(zinc methacrylate) coating with alloyed green-emitting CdZnSeS/ZnS quantum dots (QDs@PZnMA) together with high refractive-index BaTiO₃ nanoparticles to enhance the scattering coefficient of the QD films. Results demonstrate a 7.5-fold increase in the absorption coefficient, 11.3-fold increase in the scattering coefficient, 8.5-fold increase in the optical density (OD) and 8.6-fold increase in the green-light emission of QD films, compared with films that have the same mass percentage of pristine QDs. This approach provides a promising strategy for developing QD optical films with high scattering and enhanced light emission for flexible displays.

We report QD films based on a poly(zinc methacrylate) coating with alloyed green-emitting CdZnSeS/ZnS quantum dots (QDs@PZnMA) together with high refractive-index BaTiO₃ nanoparticles to enhance the scattering coefficient of the QD films.     

Nitrogen donor ligand for capping ZnS quantum dots: a quantum chemical and toxicological insight

Nanoparticles having strong optical and electronic properties are the most widely used materials in sensor development. Since the target analyte interacts directly with the surface of the material, the choice of ligand for functionalizing the surface of the material is the key for its further applications. The functionalized surface of the material makes it suitable for required applications as it controls the size of the particle during its growth from the solution phase. Biomolecule capped nanomaterials are favourable for various applications in bio-sensing. In the present work, an attempt has been made to explore the biologically active molecule imidazole as capping agent for ZnS semiconductor nanoparticles or quantum dots (QDs). This work explores the possibility of replacing conventional thiol-zinc bonding and hence paves new pathways for biomolecules having the possibility of being efficient capping agents. Computational chemistry has been used to study the mechanism of bonding between one of the nitrogen atoms of imidazole and the zinc ion of the ZnS QDs. The quantum chemical insight not only explores the most spontaneous interaction of zinc ion and imidazole molecule so as to act as an efficient capping agent but also explains the probable bonding site for nitrogen–zinc chemistry. The tailormade Mn doped ZnS QDs are one of the most promising materials for probe and sensor development. The ZnS core having non-toxicity and the emission in longer wavelength due to manganese makes this material highly useful biologically. The aqueous route of synthesis has been employed to obtain a highly homogeneous and pure material which was further characterized by UV (Ultra Violet spectroscopy), Spectrofluorometer, Transmission Electron Microscope and X-ray Diffraction. The toxicity at the cellular and genetic levels was also investigated to prove the potential of the imidazole capped Mn doped ZnS QD as a biocompatible material.

Nanoparticles having strong optical and electronic properties are the most widely used materials in sensor development.     

Cu–Cd–Zn–S/ZnS core/shell quantum dot/polyvinyl alcohol flexible films for white light-emitting diodes

We present a facile route for the synthesis of water-soluble Cu–Cd–Zn–S/ZnS core/shell quantum dots (QDs) by simple pH regulation. The PL spectra of Cu–Cd–Zn–S/ZnS core/shell quantum dots can cover the whole visible light region in the case of only two ratios of Cu/Cd/Zn. The emission wavelength of Cu–Cd–Zn–S/ZnS QDs can be conveniently tuned from 474 to 515 and 548 to 629 nm by adjusting the pH value when the ratios of Cu/Cd/Zn are fixed at 1 : 5 : 80 and 1 : 5 : 10, respectively. It is worth noting that under the condition of a constant Cu/Cd/Zn ratio, the UV-vis absorption spectra do not change with the fluorescence spectra, indicating that the band gap of QDs remains unchanged during the change of pH value. The photoluminescence (PL) quantum yield of the as-prepared QDs with yellow emission is up to 76%. The QDs also show excellent chemical stability after the deposition of the ZnS shell. Luminescent and flexible films are fabricated by combining Cu–Cd–Zn–S QDs with polyvinyl alcohol (PVA). The QD/PVA flexible hybrid films are successfully applied on top of a conventional blue InGaN chip for remote-type warm-white LEDs. As-fabricated warm-white LEDs exhibit a higher color rendering index (CRI) of about 89.2 and a correlated color temperature (CCT) of 4308 K.

We present a facile route for the synthesis of water-soluble Cu–Cd–Zn–S/ZnS core/shell quantum dots (QDs) by simple pH regulation.     

Photoluminescence color stability of green-emitting InP/ZnS core/shell quantum dots embedded in silica prepared via hydrophobic routes

In this work, green-emitting InP/ZnS quantum dots (QDs) modified with 1-dodecanethiol were embedded into silica by two methods to improve their photostability while maintaining a high photoluminescence quantum yield (PLQY) and a color coordinate. A monolithic QD-silica composite prepared by a non-aqueous route with tetraethyl orthosilicate and lactic acid featured low transparency, a loss of the color purity of green, and a PLQY of 1.6%, which was considerably lower than that of the original QDs (67%). The decrease of the PLQY was attributed to QD aggregation in the sol–gel process and degradation of the QDs by the acid. The alternative method involved stirring a toluene dispersion of the QDs with tetramethyl orthosilicate (TMOS) for 20 h or 7 days. The PLQY of the TMOS-modified InP/ZnS QDs (20 h) was 62%, which was only slightly lower than that of the original QDs. The PLQY decreased to 52% when the duration of aging was prolonged to 7 days. This decrease was attributed to desorption of surface modifiers from the QD surface and oxidative degradation by oxygen dissolved in toluene. Herein, the color coordinate was maintained stably. Photostability was evaluated by continuous irradiation of the samples by a blue light emitting diode. The decrease of photoluminescence (PL) intensity was suppressed by the silica encapsulation. In particular, the PL intensity of the TMOS-modified InP/ZnS QD sample (7 d) maintained 99% of its initial intensity. Silica encapsulation of InP/ZnS QDs prevented contact of the QDs with oxygen in the air, resulting in improved photostability.

We prepared and characterized green-emitting silica composites containing InP/ZnS QDs with excellent quantum yield, emission color purity, and photostability.     

High-performance inverted organic light-emitting diodes with extremely low efficiency roll-off using solution-processed ZnS quantum dots as the electron injection layer

The electron-injecting layer (EIL) is one of the key factors in inverted organic light-emitting diodes (OLEDs) to realize high electroluminescence efficiency. Here, we proposed a novel cathode-modified EIL based on ZnS quantum dots (QDs) in inverted OLEDs, and demonstrated that the device performance was dramatically improved compared to traditional ZnO EIL. The EIL of ZnS QDs may greatly promote the electron injection ability and consequently increase the charge carrier recombination efficiency for the device. We also investigated the effects of different pH values (ZnS-A, pH = 10; ZnS-B, pH = 12) on the properties of ZnS QDs. The best inverted phosphorescent OLED device employing mCP:Ir(ppy)₃ as the emission layer showed a low turn-on voltage of 2.9 V and maximum current efficiency of 61.5 cd A⁻¹. Also, the ZnS-A based device exhibits very-low efficiency roll-off of 0.9% and 4.3% at 1000 cd m⁻² and 5000 cd m⁻², respectively. Our results indicate that use of ZnS QDs is a promising strategy to increase the performance in inverted OLEDs.

The electron-injecting layer (EIL) is one of the key factors in inverted organic light-emitting diodes (OLEDs) to realize high electroluminescence efficiency.     

Solvothermal synthesis of Mn-doped CsPbCl3 perovskite nanocrystals with tunable morphology and their size-dependent optical properties

Doping metal ions in inorganic halide perovskite (CsPbX₃, X = Cl, Br, I) nanocrystals (NCs) endows the NCs with unique optical characteristics, and has thus attracted immense attention. However, controllable synthesis of high-quality doped perovskite NCs with tunable morphology still remains challenging. Here, we report a facile, effective and unified strategy for the controllable synthesis of Mn-doped CsPbCl₃ quantum dots (QDs) and nanoplatelets (NPLs) via a single-step solvothermal method. The incorporation of Mn²⁺ into CsPbCl₃ NCs introduces new broad photoluminescence (PL) emission from Mn²⁺ while maintaining the structure of host CsPbCl₃ NCs nearly intact. The PL intensity, emission peak position and size of the NCs can be accurately adjusted by altering the experimental parameters such as Mn-to-Pb feed ratio and reaction time. Especially, by changing the amount of ligands, Mn-doped CsPbCl₃ QDs, NPLs or their mixtures can be obtained. Both of the Mn-doped QDs and NPLs exhibit a size-dependent quantum confinement effect, which is confirmed by the relationship between the size of NCs and the exciton emission peaks. The solvothermal reaction condition plays an important role for the precise control of the structure, morphology and PL properties of the Mn-doped NCs. The as-prepared Mn-doped CsPbCl₃ NPLs with thickness down to ∼2 nm exhibit a PL quantum yield (PLQY) of more than 22%. This work introduces a new strategy for the controllable synthesis of Mn-doped perovskite NCs, which provides ideas for the in-depth study of the dope-and-grow process and can be extended to approaches of doping other metal ions.

A facile solvothermal reaction strategy was developed to obtain Mn-doped CsPbCl₃ nanocrystals with tunable morphology and optical properties.     

Facile one-step synthesis of quaternary AgInZnS quantum dots and their applications for causing bioeffects and detecting Cu2+

Water-soluble AgInZnS quantum dots (AIZS QDs) were synthesized with glutathione (GSH) as a stabilizer by a facile one-step method based on a hydrothermal reaction between the nitrate salts of the corresponding metals and sodium sulfide as a sulfide precursor at 110 °C. The optimal reaction conditions (temperature, time, pH, and the molar ratios of the precursors) were studied. According to the data from TEM, XPS, and XRD, AIZS QDs were characterized with excellent optical properties. The results showed that the aqueous-dispersible AIZS QDs were quasi-spherical and their average diameter was 3.51 nm. Furthermore, the cytotoxicity of AIZS QDs was investigated by microcalorimetry and microscopy techniques (confocal microscopy and TEM). The data revealed that AIZS QDs exhibited low toxicity, biocompatibility, and good water stability, due to which they could be used as a fluorescent probe for bioimaging and labeling. In addition, AIZS QDs could be used as a sensor to detect Cu²⁺ because the fluorescence of AIZS QDs was quenched by Cu²⁺.

Water-soluble AgInZnS quantum dots were synthesized with glutathione as a stabilizer by a facile one-step method based on a hydrothermal reaction at 110 °C. It exhibited excellent optical properties, which can be used as sensor to detect Cu²⁺.     

Synthesis of water-soluble and bio-taggable CdSe@ZnS quantum dots

Many synthesized semiconductor QDs materials are formed using trioctylphosphine oxide (TOPO) but it requires high temperature, is very expensive and is also hydrophobic. Our study deals with selective syntheses of CdSe and core–shell CdSe/ZnS quantum dots (QDs) in aqueous solution by a simple heating and refluxing method. It is more hydrophilic, needs less temperature, is economically viable and is eco-friendly. Bio-ligands, such as thioacetamide, itaconic acid and glutathione, were used as stabilizers for the biosynthesis of QDs. A simplified aqueous route was used to improve the quality of the colloidal nanocrystals. As a result, highly monodisperse, photoluminescent and biocompatible nanoparticles were obtained. The synthesized QDs were characterized by XRD, FTIR, confocal microscopy, ultraviolet (UV) absorption and photoluminescence (PL). The size of synthesized QDs was observed as 5.74 nm and the core–shell shape was confirmed by using XRD and confocal microscopy respectively. The QD nanoparticles showed antibacterial activity against pathogenic bacteria. The QDs could be applied for biological labelling, fluorescence bio-sensing and bio-imaging etc.

Mystristic capped CdSe QDs with schematic diagram and formation mechanism of bio-taggable CdSe@ZnS QDs.     

Full-color-emitting (CuInS2)ZnS-alloyed core/shell quantum dots with trimethoxysilyl end-capped ligands soluble in an ionic liquid

Zinc-copper-indium sulfide (ZCIS)-alloyed quantum dots are emerging as a new family of low toxic I–III–VI semiconductors due to their broad and color-tunable emissions as well as large Stokes shifts. Here, we fabricated a series of ZCIS QDs with tunable PL wavelengths and band-gap energies via a facile strategy by varying the ratio of A1–3 stock (Cu⁺/In³⁺) to the B stock (Zn²⁺) content. The ZnS shell was formed to improve the PL emission efficiency of the core nanoparticles and the PL emission wavelength of the resulting ZCIS/ZnS NCs gradually blue-shifted with an increase in the number of shell layers, resulting in a wide range of emissions from 800 nm to 518 nm that can be tuned by the core compositions or shell layer numbers for ZCIS/ZnS. Finally, the long-chain ligands dodecanethiol/octadecylamine on the quantum dots'' surface were efficiently replaced by (3-mercaptopropyl)trimethoxysilane, thus enabling their solubility in an ionic liquid, which was confirmed via GC-MS. It also benefited for the co-dissolution of the polymers and chemical binding with other materials through the reactive silanol group, which provide stable and well-distributed ZCIS/ZnS QDs composites or surface coating by the QDs.

ZCIS QDs were fabricated by varying ratio stock A to stock B. PL intensity enhanced and blue shift as shell layers increase. Emissions covering 800 nm to 518 nm tuned by compositions or shell layers. Ligand exchanged by MPtMS enable solubility in IL.     

Water soluble cadmium selenide quantum dots for ultrasensitive detection of organic,inorganic and elemental mercury in biological fluids and live cells

Mercury exists in organic, inorganic, and elemental forms; all of them are highly toxic. A sensor which could detect all forms of mercury below the permissible level in environmental and biological samples would be advantageous. A facile method to synthesize N-acetyl cysteine capped cadmium selenide quantum dots (CdSe QDs) with an emission at 554 nm was reported. CdSe QDs showed high sensitivity and selectivity toward Hg in aqueous media as well as biological fluids like simulated cerebrospinal fluid, saliva, and urine, and also in natural fluids like juices of tomato, sugarcane, and lime. The sensing mechanism is attributed to the interactions between Hg and CdSe QDs inducing fluorescence quenching. The limit of detection is 1.62, 0.75, and 1.27 ppb for organic, inorganic and elemental mercury, respectively, which is below WHO guidelines. The suitability of the sensor for estimating Hg in biological fluids was demonstrated by recovery experiments. Besides sensing, a two color cell imaging method was developed employing CdSe QDs and acridine orange. Using this method, the uptake of Hg in living cells was demonstrated.

CdSe QDs fluorescence is highly selective and sensitive to mercury.     

Near-complete photoluminescence retention and improved stability of InP quantum dots after silica embedding for their application to on-chip-packaged light-emitting diodes

Silica is the most commonly used oxide encapsulant for passivating fluorescent quantum dots (QDs) against degradable conditions. Such a silica encapsulation has been conventionally implemented via a Stöber or reverse microemulsion process, mostly targeting CdSe-based QDs to date. However, both routes encounter a critical issue of considerable loss in photoluminescence (PL) quantum yield (QY) compared to pristine QDs after silica growth. In this work, we explore the embedment of multishelled InP/ZnSeS/ZnS QDs, whose stability is quite inferior to CdSe counterparts, in a silica matrix by means of a tetramethyl orthosilicate-based, waterless, catalyst-free synthesis. It is revealed that the original QY (80%) of QDs is nearly completely retained in the course of the present silica embedding reaction. The resulting QD–silica composites are then placed in degradable conditions such UV irradiation, high temperature/high humidity, and operation of an on-chip-packaged light-emitting diode (LED) to attest to the efficacy of silica passivation on QD stability. Particularly, the promising results with regard to device efficiency and stability of the on-chip-packaged QD-LED firmly suggest the effectiveness of the present silica embedding strategy in not only maximally retaining QY of QDs but effectively passivating QDs, paving the way for the realization of a highly efficient, robust QD-LED platform.

Silica embedding strategy enabling a nearly full PL retention of the original QY of InP QDs is proposed for the realization of a highly efficient, robust QD-LED platform.