CdS Shell Research Articles

Comparative investigation of magneto-fluorescent core@shell nanostructures prepared using hard and soft ferrite as core

The paper focuses on the potential of magneto-fluorescent nanostructures intended to join simultaneously several functions of dissimilar core and shell material into a single entity. Two different types of magneto-fluorescent nanostructures with a broad array of physicochemical properties are premeditated and collated here. Strontium hexaferrite (Hard ferrite) core with CdS shell and Nickel Zinc ferrite (Soft ferrite) core with CdS shell are the two sets of magneto fluorescent nanostructures that were designed. Magnetic and optical analysis of both sets provides divergent outcomes. The shape of the derivative hysteresis curve gives a direct indication of the dissimilar nature (superparamagnetic & Permanent magnetic) of magnetic cores respectively. Optical results depict that both sets of magneto-fluorescent nanostructures are highly stable showing emission only in the position of the CdS shell only.

Colossal Core/Shell CdSe/CdS Quantum Dot Emitters.

Single-photon sources are essential for advancing quantum technologies with scalable integration being a crucial requirement. To date, deterministic positioning of single-photon sources in large-scale photonic structures remains a challenge. In this context, colloidal quantum dots (QDs), particularly core/shell configurations, are attractive due to their solution processability. However, traditional QDs are typically small, about 3 to 6 nm, which restricts their deterministic placement and utility in large-scale photonic devices, particularly within optical cavities. The largest existing core/shell QDs are a family of giant CdSe/CdS QDs, with total diameters ranging from about 20 to 50 nm. Pushing beyond this size limit, we introduce a synthesis strategy for colossal CdSe/CdS QDs, with sizes ranging from 30 to 100 nm, using a stepwise high-temperature continuous injection method. Electron microscopy reveals a consistent hexagonal diamond morphology composed of 12 semipolar {101̅1} facets and one polar (0001) facet. We also identify conditions where shell growth is disrupted, leading to defects, islands, and mechanical instability, which suggest synthetic requirements for growing crystalline particles beyond 100 nm. The stepwise growth of thick CdS shells on CdSe cores enables the synthesis of emissive QDs with long photoluminescence lifetimes of a few microseconds and suppressed blinking at room temperature. Notably, QDs with 80 and 100 CdS monolayers exhibit high single-photon emission purity with second-order photon correlation g(2)(0) values below 0.2.

Synthesis and performance optimization of CsPbBr3/CdS core/shell lead halide perovskite nanocrystals by an ion exchange method.

All-inorganic lead halide perovskite nanocrystals (NCs) have excellent optoelectronic properties and promising applications. Improving the stability of inorganic halide NCs and optimizing their photoluminescence quantum yields (PLQY) has become an urgent task. Constructing core-shell structures is an effective method to improve the environmental stability and PLQY, however, realizing core-shell structured perovskite NCs with good dispersion and multiple perovskites encapsulated within the shell material remains challenging. In this work, CdS shells were grown on the surface of CsPbBr3 NCs by ion-exchange method utilizing perovskite NCs with their ionic properties, and the effectiveness of the surface shell protection is reflected in its enhancement of long-term storage stability, storage stability in water, and thermal stability of NCs. In addition, the PLQY and exciton binding energies of CsPbBr3/CdS NCs are increased. Finally, the NCs were packaged into green emitting LED devices and performed high stability. The results will facilitate the further commercialization of all-inorganic lead halide perovskite materials for optoelectronic devices.

Exploring photocurrent effects as a function of CdS shell in ultrasmall quantum dots

In this study, we report the photocurrent effects in CdSe/CdS ultrasmall quantum dots (USQDs). The photocurrent effects can be observed when photons with energy higher than the band gap energy illuminate the USQDs, generating of charge carries. Here we use two types of USQDs to analyze these effects: CdSe and CdSe/CdS core/shell. The Raman spectrum was used to confirm the presence or absence of the shell. The CdSe USQDs exhibited a photocurrent effect consistent with the pattern typically observed in semiconductor materials. The sample exhibited a rise time of 1.26 s when the light was turned on and a decay time of 0.70 s when the light was turned off, reaching a maximum current value of 12.90 pA. However, an overshoot phenomenon was observed in the CdSe/CdS USQDs when the light was turned off. This effect is related to the accumulation of charge carriers that appear when the USQDs are subjected to an electric field and the presence of light. Thus, this accumulation caused by the potential barrier formed by the shell is released when the light is turned off. The sample exhibited a rise time of 2.28 s when the light was turned on and a decay time of 2.59 s when the light was turned off, reaching a maximum current value of 70.51 pA. Therefore, we have demonstrated that it is possible to explore the photocurrent effects in CdSe/CdS USQDs.

Correlating semiconductor nanoparticle architecture and applicability for the controlled encoding of luminescent polymer microparticles

Luminophore stained micro- and nanobeads made from organic polymers like polystyrene (PS) are broadly used in the life and material sciences as luminescent reporters, for bead-based assays, sensor arrays, printable barcodes, security inks, and the calibration of fluorescence microscopes and flow cytometers. Initially mostly prepared with organic dyes, meanwhile luminescent core/shell nanoparticles (NPs) like spherical semiconductor quantum dots (QDs) are increasingly employed for bead encoding. This is related to their narrower emission spectra, tuneability of emission color, broad wavelength excitability, and better photostability. However, correlations between particle architecture, morphology, and photoluminescence (PL) of the luminescent nanocrystals used for encoding and the optical properties of the NP-stained beads have been rarely explored. This encouraged us to perform a screening study on the incorporation of different types of luminescent core/shell semiconductor nanocrystals into polymer microparticles (PMPs) by a radical-induced polymerization reaction. Nanocrystals explored include CdSe/CdS QDs of varying CdS shell thickness, a CdSe/ZnS core/shell QD, CdSe/CdS quantum rods (QRs), and CdSe/CdS nanoplatelets (NPLs). Thereby, we focused on the applicability of these NPs for the polymerization synthesis approach used and quantified the preservation of the initial NP luminescence. The spectroscopic characterization of the resulting PMPs revealed the successful staining of the PMPs with luminescent CdSe/CdS QDs and CdSe/CdS NPLs. In contrast, usage of CdSe/CdS QRs and CdSe QDs with a ZnS shell did not yield luminescent PMPs. The results of this study provide new insights into structure–property relationships between NP stained PMPs and the initial luminescent NPs applied for staining and underline the importance of such studies for the performance optimization of NP-stained beads.

Well-type thick-shell quantum dots combined with double hole transport layers device structure assisted realization of high-performance quantum dot light-emitting diodes

Quantum dot (QD) light-emitting diodes (QLEDs) are promising for next-generation lighting and displays. Considering the optimization design of both the QD and device structure is expected to improve the QLED's performance significantly but has rarely been reported. Here, we use the thick-shell QDs combined with a dual-hole transport layer device structure to construct a high-efficiency QLED. The optimized thick-shell QDs with CdS/CdSe/CdS/ZnS seed/spherical quantum well/shell/shell geometry exhibit a high photoluminescence quantum yield of 96% at a shell thickness of 5.9 nm. The intermediate emissive CdSe layer with coherent strain ensures defect-free growth of the thick CdS and ZnS outer shells. Based on the orthogonal solvents assisted Poly-TPD&PVK dual-hole transport layer device architecture, the champion QLED achieved a maximum external quantum efficiency of 22.5% and a maximum luminance of 259955 cd m-2, which are 1.6 and 3.7 times that of thin-shell QDs based devices with single hole transport layer, respectively. Our study provides a feasible idea for further improving the performance of QLED devices.

Localization-of-light-induced stimulated Mie scattering: Laser pulse duration adjustment in a broad range

Backward stimulated Mie scattering (BSMS) holds significant potential across various fields due to its superior properties. In this study, we demonstrate that metal-semiconductor hybrids of CdS shell and Au core markedly enhanced the BSMS compared with pure CdS nanoparticles. Theoretical analysis suggests that the enhancement should be attributed to multi-photon excitation and increased Anderson localization of light. The localized light interacts with the incident light, creating conditions conducive to BSMS, thereby improving efficiency and reducing the threshold. The enhanced localization of light is a result of the increased nonlinear refractive index induced by electron-sink effect. Importantly, we propose a novel strategy, on the basis of BSMS, to adjust the pulse duration of laser output in a broad range without any frequency shift.

Infrared Imaging Using Thermally Stable HgTe/CdS Nanocrystals.

Transferring nanocrystals (NCs) from the laboratory environment toward practical applications has raised new challenges. HgTe appears as the most spectrally tunable infrared colloidal platform. Its low-temperature synthesis reduces the growth energy cost yet also favors sintering. Once coupled to a read-out circuit, the Joule effect aggregates the particles, leading to a poorly defined optical edge and large dark current. Here, we demonstrate that CdS shells bring the expected thermal stability (no redshift upon annealing, reduced tendency to form amalgams, and preservation of photoconduction after an atomic layer deposition process). The electronic structure of these confined particles is unveiled using k.p self-consistent simulations showing a significant exciton binding energy of ∼200 meV. After shelling, the material displays a p-type behavior that favors the generation of photoconductive gain. The latter is then used to increase the external quantum efficiency of an infrared imager, which now reaches 40% while presenting long-term stability.

Analytical investigation of CdSe/CdS/ZnSe‐based single‐core double‐shell nanotextured vertical nanopillar array antenna for broadband photodetection applications

SummaryThe photon‐trapping nanostructures greatly contributes in minimizing the light reflectance losses occurring due to air–semiconductor refractive mismatch in photodetector devices. Here we have proposed a vertically oriented CdSe/CdS/ZnSe tri material‐based multiple core–shell nanopillar array structure to act as a light‐trapping efficient antenna for broadband photodetection applications. The nanopillar structure consist of diamond shaped nanotexturization over its three layer pillar interfaces. The proposed nanotexturization over the triple‐layered nanopillar structure would feature multiple scattering mechanisms for the trapped photons enhancing their optical path length along with the defect‐free confinement of the exciton pairs. The lattice compatibility of the CdS and ZnS shell layers forms a bridge between the lattice‐mismatched CdSe core and ZnSe shell leading towards the attainment of a reduced strain as well as high photochemical stability and photo quantum efficiency. As compared to the single‐layered CdSe/ZnSe nanotextured core–shell nanopillar structure the double‐layered nanotextured CdSe/CdS/ZnSe exhibits a high photoresponsivity of 0.425 A/W and external quantum efficiency of 0.98 is attained. The obtained results exhibit that the double‐shell layered‐based nanotextured nanopillar array structure would be a well‐competent alternative as compared to the planar counterpart for next‐generation photodetector applications.

Electrochemical control of photoluminescence in pure wurtzite CdSe/CdS core/shell nanocrystals

Spectroelectrochemical methods are employed to systematically investigate the impacts of external charge filling in three pure wurtzite CdSe/CdS core/shell nanocrystals (NCs) with different shell thicknesses. We observed that electrons can penetrate the thick CdS shell and inject into the conduction band with an abnormal brightening, while holes are blocked. The formed negative trions result in a different spectral shift according to the size of the NCs, with a redshift of 3.7 nm for 12.5 nm NCs and almost no movement for 23.4 nm NCs. Meanwhile, due to the formation of biexcitons, a variational spectral blueshift with the NCs' size can be determined in time-resolved photoluminescence spectroscopy. This indicates that the binding energy of both biexcitons and negatively charged excitons can be regulated by controlling the shell thickness. Extra charges can also be used to activate/passivate trap states, thereby confirming that the 12.5 nm sample has better surface/interface quality.

Suppressed Magnitude of Spectral Diffusion in Cube-Shaped CdSe/CdS Core/Shell Nanocrystals with Exceedingly Stable Photoluminescence.

Colloidal semiconductor nanocrystals are promising candidates for quantum light sources, yet their application has been impeded by photoluminescence instability due to blinking and spectral diffusion. This study introduces a new category of cube-shaped CdSe/CdS core/shell nanocrystals with exceptionally stable photoluminescence characteristics. Under continuous excitation, the emissive quantum state remained consistent without alterations of the charge state for 4000 s, and the average photon energy variation stayed within the bounds of spectral resolution throughout this extended duration. Systematic examination of single-nanocrystal photoluminescence, upon variation of the core and shell dimensions, revealed that a thicker CdS shell and increased core edge length significantly curtail spectral diffusion, considering that the nanocrystals possess well-controlled CdSe-CdS and facet-ligand interfaces. This study advances the optimization of colloidal semiconductor nanocrystals as high-performance quantum light sources.

Atomic Au3Cu Palisade Interlayer in Core@Shell Nanostructures for Efficient Kirkendall Effect Mediation.

Plasmonic Cu@semiconductor heteronanocrystals (HNCs) have many favorable properties, but the synthesis of solid structures is often hindered by the nanoscale Kirkendall effect. Herein, we present the use of an atomically thin Au3Cu palisade interlayer to reduce lattice mismatch and mediate the Kirkendall effect, enabling the successive topological synthesis of Cu@Au3Cu@Ag, Cu@Au3Cu@Ag2S, and further transformed solid Cu@Au3Cu@CdS core-shell HNCs via cation exchange. The atomically thin and intact Au3Cu palisade interlayer effectively modulates the diffusion kinetics of Cu atoms as demonstrated by experimental and theoretical investigations and simultaneously alleviates the lattice mismatch between Cu and Ag as well as Cu and CdS. The Cu@Au3Cu@CdS HNCs feature exceptional crystallinity and atomically organized heterointerfaces between the plasmonic metal and the semiconductor. This results in the efficient plasmon-induced injection of hot electrons from Cu@Au3Cu into the CdS shell, enabling the Cu@Au3Cu@CdS HNCs to achieve high activity and selectivity for the photocatalytic reduction of CO2 to CO.

Enhancement of Optical Gain in Colloidal CdSe/CdS/ZnS Quantum Dots through Nanosecond Optical Pumping.

Optical gain and lasing in colloidal nanocrystals are often hindered by sub-nanosecond rapid Auger non-radiative recombination, especially under continuous wave optical or electrical excitation. This study demonstrates amplified spontaneous emission (ASE) from CdSe/CdS/ZnS quantum dot (QD) solids through prolonged pulsed optical pumping over 10 ns. The incorporation of CdS and ZnS double shells on CdSe QDs effectively decelerates the Auger process in multiexcitonic states by extending the electron wave function and enhancing dielectric screening. Furthermore, we engineer smooth, densely packed QD solid films that efficiently guide the optical mode, achieving substantial net gain values under nanosecond pumping. The proposed approach helps observe ASE with gain thresholds of 0.84 and 1.5 mJ/cm2 under optical pumping pulse widths of 6 and 15 ns, respectively. This advancement can promote continuous pumping in colloidal QD gain systems, opening new avenues for optoelectronic applications.

An ′On‐off‐on′ Fluorescence Sensor Based on CdSe Quantum Dots for the Selective Detection of Cd2+

AbstractIn this work, an “on‐off‐on” nanoprobe for specific detection of Cd2+ was constructed using N‐acetyl‐l‐cysteine (NAC)‐modified CdSe quantum dots (QDs). The prepared CdSe QDs exhibit characteristic green fluorescence. The adsorbed S2− on the surface of CdSe QDs leads to dangling bonds and causes the fluorescence quenching of QDs, where the fluorescence of the system turns “off“. When Cd2+ exists, it can react with the adsorbed S2− to form CdS shell, resulting in the fluorescence enhancement of CdSe QDs, where the fluorescence of the system turns “on”. Due to the similar lattice structure between CdSe and CdS, CdSe/CdS can be produced by shell deposition, while self‐nucleation of metal sulfide is observed in the presence of other metal ions. Thus, the developed nanoprobe shows high selectivity for Cd2+. Under the optimum sensing conditions, the fluorescence sensing signal of CdSe QDs depends linearly on the Cd2+ in the range of 0.2–9 μM. The limit of detection (LOD) and limit of quantification (LOQ) of this nanoprobe is 27 nM and 90 nM, respectively. Furthermore, the proposed nanoprobe can monitor Cd2+ in drinking water with a recovery rate between 95.82 % and 102.00 %, indicating its good practicability and applicability for real sample analysis.

Efficient Photoelectrochemical Hydrogen Generation Based on Core Size Effect of Heterostructured Quantum Dots.

Colloidal quantum dots (QDs) are shown to be effective as light-harvesting sensitizers of metal oxide semiconductor (MOS) photoelectrodes for photoelectrochemical (PEC) hydrogen (H2) generation. The CdSe/CdS core/shell architecture is widely studied due to their tunable absorption range and band alignment via engineering the size of each composition, leading to efficient carrier separation/transfer with proper core/shell band types. However, until now the effect of core size on the PEC performance along with tailoring the core/shell band alignment is not well understood. Here, by regulating four types of CdSe/CdS core/shell QDs with different core sizes (diameter of 2.8, 3.1, 3.5, and 4.8 nm) while the thickness of CdS shell remains the same (thickness of 2.0 ± 0.1 nm), the Type II, Quasi-Type II, and Type I core/shell architecture are successfully formed. Among these, the optimized CdSe/CdS/TiO2 photoelectrode with core size of 3.5 nm can achieve the saturated photocurrent density (Jph) of 17.4 mA cm-2 under standard one sun irradiation. When such cores are further optimized by capping alloyed shells, the Jph can reach values of 22 mA cm2 which is among the best-performed electrodes based on colloidal QDs.

Band-Edge Energy Levels of Dynamic Excitons in Cube-Shaped CdSe/CdS Core/Shell Nanocrystals.

An electron-hole pair in a cube-shaped CdSe/CdS core/shell nanocrystal exists in the form of dynamic excitons across the strongly and weakly confined regimes under ambient temperatures. Photochemical doping is applied to distinguish the band-edge electron and hole levels, confirming an effective mass model with universal constants. Reduction of the optical bandgap upon epitaxy of the CdS shells is caused by lowering the band-edge electron level and barely affecting the band-edge hole level. Similar shifts of the electron levels, yet retaining the hole levels, can switch the order in energy of the three lowest-energy transitions. Thermal distribution of 1-4 electrons among the two thermally accessible electron levels follows number-counting statistics, instead of Fermi-Dirac distribution.

Preparation of N-A Cysteine-capped CdTe/CdS/ZnS core/shell/shell QDs as a Selective Probe for Detecting Damaged DNA

In this study, NAC-capped CdTe/CdS/ZnS core/double shell QDs were synthesized in an aqueous medium to investigate their utility in distinguishing normal DNA from mutated DNA extracted from biological samples. Following the interaction between the synthesized QDs with DNA extracted from leukemia cases (represents damaged DNA) and that of healthy donors (represents undamaged DNA), differential fluorescent emission maxima and intensities were observed. It was found that damaged DNA from leukemic cells DNA-QDs conjugates at 585 nm while intact DNA (from healthy subjects) DNA–QDs conjugates at 574 nm. The obtained results from the optical analyses indicate that the prepared QDs could be utilized as probe for detecting disrupted DNA that is associated with a number of diseases including malignancies. Additionally, the manufactured NAC-CdTe core with CdS shell and ZnS shell QDs were further characterized by high-resolution transmission using field emission scanning electron microscopy (FESEM), energy dispersive X-ray fluorescence (EDX), X-ray diffraction (XRD), infrared spectrum (IR), UV-vis absorbance, photoluminescence (PL) and absorbency intensity using the fully automatic ELISA. The XRD results revealed the formation of NAC-CdTe/CdS/ZnS QDs with a grain size of 5.7 nm. While EDX assay emphasizes the compound content of Cd, S, Zn and Te elements. Whereas SEM test’s findings propose the spherical size of NAC- CdTe/CdS/ZnS QDs within the range of 10–40 nm. The demonstrated mono-dispersed lattice structure of NAC-CdTe core with CdS shell and ZnS shell QDs has superior PL emission properties at [Formula: see text] of [Formula: see text]600 nm and UV-Vis absorption bands at 350 nm. Overall, this study suggests that the synthesized QDs could be employed in developing optical biosensors for a variety of biomedical applications to improve early detection of diseases marked by damaged DNA profile including cancers.

Construction of Core-shell Sb2 s3 @Cds Nanorod with Enhanced Heterointerface Interaction for Chromium-Containing Wastewater Treatment.

How to collaboratively reduce Cr(VI) and break Cr(III) complexes is a technical challenge to solve chromium-containing wastewater (CCW) pollution. Solar photovoltaic (SPV) technology based on semiconductor materials is a potential strategy to solve this issue. Sb2 S3 is a typical semiconductor material with total visible-light harvesting capacity, but its large-sized structure highly aggravates disordered photoexciton migration, accelerating the recombination kinetics and resulting low-efficient photon utilization. Herein, the uniform mesoporous CdS shell is in situ formed on the surface of Sb2 S3 nanorods (NRs) to construct the core-shell Sb2 S3 @CdS heterojunction with high BET surface area and excellent near-infrared light harvesting capacity via a surface cationic displacement strategy, and density functional theory thermodynamically explains the breaking of SbS bonds and formation of CdS bonds according to the bond energy calculation. The SbSCd bonding interaction and van der Waals force significantly enhance the stability and synergy of Sb2 S3 /CdS heterointerface throughout the entire surface of Sb2 S3 NRs, promoting the Sb2 S3 -to-CdS electron transfer due to the formation of built-in electric field. Therefore, the optimized Sb2 S3 @CdS catalyst achieves highly enhanced simulated sunlight-driven Cr(VI) reduction (0.154 min-1 ) and decomplexation of complexed Cr(III) in weakly acidic condition, resulting effective CCW treatment under co-action of photoexcited electrons and active radicals. This study provides a high-performance heterostructured catalyst for effective CCW treatment by SPV technology.

Hollow Spherical Pd/CdS/NiS with Carrier Spatial Separation for Photocatalytic Hydrogen Generation.

Inspired by the unique properties of the three-dimensional hollow nanostructures in the field of photocatalysis, as well as the combination of co-catalyst, porous hollow spherical Pd/CdS/NiS photocatalysts are prepared by stepwise synthesis. The results show that the Schottky junction between Pd and CdS accelerates the transport of photogenerated electrons, while a p-n junction between NiS and CdS traps the photogenerated holes. As co-catalysts, the Pd nanoparticles and the NiS are loaded inside and outside the hollow CdS shell layer, respectively, which combines with the particular characteristic of the hollow structure, resulting in a spatial carrier separation effect. Under the synergy of the dual co-catalyst loading and hollow structure, the Pd/CdS/NiS has favorable stability. Its H2 production under visible light is significantly increased to 3804.6 μmol/g/h, representing 33.4 times more than that of pure CdS. The apparent quantum efficiency is 0.24% at 420 nm. A feasible bridge for the development of efficient photocatalysts is offered by this work.

Dual charge-accepting engineering modified AgIn5S8/CdS quantum dots for efficient photocatalytic hydrogen evolution overall H2S splitting

Low charge carrier separation and transfer efficiency continues to be the major obstacle to harvest solar energy to split hydrogen sulfide (H2S) as hydrogen source for H2 production with value-added utilization for waste by-products. Herein, we designed a Type-II core/shell AgIn5S8/CdS (AIS/CdS) quantum dots (QDs) photocatalyst capped with short-chain inorganic sulfide ion (S2−) ligand with dual charge-accepting engineering to promote charge carrier extraction and faster photogenerated electron transfer. Transient absorption spectroscopy analysis demonstrates that the excited electrons are fast injected into CdS shell from AIS core within 1.7 ps, instead of transferring to sub-bandgap states. Consequently, the highest photocatalytic hydrogen evolution rate of AIS/CdS QDs with S2- ligand is 12.74 mmol g−1 h−1 that is more than four times of pristine AIS core. This work offers insightful guidance on the rational design of charge-accepting engineering QDs-based photocatalysts, thereby stimulating solar to hydrogen generation and resource utilization of pollutants.