- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Atomically-thin population of colloidal CdSe nanoplatelets: growth of rolled-up nanosheets and strong circular dichroism induced by ligand exchange
摘要： Colloidal two-dimensional cadmium chalcogenides nanoplatelets have recently emerged as a class of semiconductor nanoparticles with the narrowest emission and absorption excitonic bands that are of interest for optical applications. Here, we have developed a synthesis protocol for 2.5 monolayers (ML) thick CdSe nanosheets as a single population. We found that a two-step synthesis in the presence of water promoted the growth of atomically-thin nanosheets with high structural and morphological perfection. Using seeded-growth technique, we extended the lateral size of nanosheets up to 400 nm, which led to the formation of multiwall rolled-up nanostructures. Ligand exchange of native oleic acid, attached to Cd-rich (001) planes, with achiral thioglycolic acid and chiral N-acetylcysteine retains a scroll-like morphology of nanosheets, in contrast to thicker 3.5 ML population. A reorientation from the [110] to [100] folding direction was found during the change from an achiral to a chiral ligand. In the case of ligand exchange with chiral N-acetyl-L- or D-cysteine, we demonstrated that 2.5 ML CdSe nanosheets with 400 nm lateral size have circular dichroism with dissymmetry g-factor up to 3?10-3. Strong circular dichroism found for colloidal CdSe nanosheets makes them a promising candidate for polarization-enabled applications, while the growth protocol of the thinnest CdSe nanosheets enriches the known synthesis methods of a set of CdSe nanoplatelet populations.
关键词： nanoplatelets,colloidal,circular dichroism,CdSe,ligand exchange
更新于2025-09-12 10:27:22
-
Low‐Threshold Amplified Spontaneous Emission and Lasing from Thick‐Shell CdSe/CdS Core/Shell Nanoplatelets Enabled by High‐Temperature Growth
摘要： Colloidal semiconductor nanoplatelets (NPLs) have recently emerged as highly promising optical gain medium because of their superior optical properties. Here, the shell-thickness-dependent optical gain properties of CdSe/CdS core/shell NPLs synthesized by high-temperature growth are systematically investigated for the first time. The core/shell NPLs show the increased quantum yields and enhanced photostability as well as clear reduced emission blinking, thanks to the preferable passivation of nonradiative surface defects by the growth of the high-quality CdS shells under high reaction temperature. Meanwhile, the amplified spontaneous emission (ASE) performance of CdSe/CdS NPLs indicates a nonmonotonic dependence on the shell thickness. The ASE threshold is achieved as low as ≈4.4 μJ cm?2 for thick-shell NPLs with six monolayer CdS shells, and exhibiting ultrafast transient dynamics process (≈11 ps). Besides, an extremely long lifetime (>800 ps) and large bandwidth (>140 nm) of optical gain are observed by employing ultrafast transient absorption spectroscopy. Finally, a thick-shell NPLs vertical cavity surface-emitting laser is developed, which demonstrates spatially directional single-mode operation with an ultralow lasing threshold of ≈1.1 μJ cm?2. These excellent results are attributed to the remarkable optical gain performance of core/shell NPLs and represent an important step toward practical NPL laser devices.
关键词： CdSe/CdS,amplified spontaneous emission,nanoplatelets,vertical cavity surface-emitting laser,optical gain
更新于2025-09-12 10:27:22
-
Record High External Quantum Efficiency of 19.2% Achieved in Light‐Emitting Diodes of Colloidal Quantum Wells Enabled by Hot‐Injection Shell Growth
摘要： Colloidal quantum wells (CQWs) are regarded as a highly promising class of optoelectronic materials, thanks to their unique excitonic characteristics of high extinction coefficients and ultranarrow emission bandwidths. Although the exploration of CQWs in light-emitting diodes (LEDs) is impressive, the performance of CQW-LEDs lags far behind other types of soft-material LEDs (e.g., organic LEDs, colloidal-quantum-dot LEDs, and perovskite LEDs). Herein, high-efficiency CQW-LEDs reaching close to the theoretical limit are reported. A key factor for this high performance is the exploitation of hot-injection shell (HIS) growth of CQWs, which enables a near-unity photoluminescence quantum yield (PLQY), reduces nonradiative channels, ensures smooth films, and enhances the stability. Remarkably, the PLQY remains 95% in solution and 87% in film despite rigorous cleaning. Through systematically understanding their shape-, composition-, and device-engineering, the CQW-LEDs using CdSe/Cd0.25Zn0.75S core/HIS CQWs exhibit a maximum external quantum efficiency of 19.2%. Additionally, a high luminance of 23 490 cd m?2, extremely saturated red color with the Commission Internationale de L’Eclairage (CIE) coordinates of (0.715, 0.283), and stable emission are obtained. The findings indicate that HIS-grown CQWs enable high-performance solution-processed LEDs, which may pave the path for future CQW-based display and lighting technologies.
关键词： core/shell structures,colloidal quantum wells,nanoplatelets,hot injection,light-emitting diodes
更新于2025-09-12 10:27:22
-
Precursor-Mediated Synthesis of Shape-controlled Colloidal CsPbBr <sub/>3</sub> Perovskite Nanocrystals and their Nanofiber-Directed Self-assembly
摘要： Shape control is often necessary to tune the optical and electronic properties of nanocrystals (NCs) and is mostly achieved through manipulation of surface ligands and processing conditions. Here we present a versatile synthesis of colloidal CsPbBr3 perovskite NCs of various shapes (nanorods, nanocubes and nanoplatelets) from an inexpensive steroidal Cs precursor: cesium cholate (CsCh). Cesium cholate has several advantages over the most commonly used Cs-precursor (cesium oleate or Cs2CO3 or CsOAc) such as low-cost, non-hygroscopicity and better reproducibility in the perovskite synthesis. Due to the solubility of this Cs-precursor in polar solvents such as methanol, a miniscule polar environment is created during the nucleation and growth of the nanocrystals leading to the serendipitous formation of nanorods at 180 ℃, whereas using a biphasic mixture of 1-octadecene and methanol, the morphology changes to nanocubes. By lowering the reaction temperature (90 ℃), nanoplatelets with 8-9 monolayers thicknesses are formed. These colloidal NCs of variety of shapes are strongly luminescent with a green emission having narrow emission linewidths (16-17 nm) and high quantum yields (96% for nanocubes, 94% for nanoplatelets). Furthermore, hybrid materials of nanocubes and organogel of a dimeric bile acid-derived ester gelator are obtained through co-assembly in which nanocubes arrange along nanofibers with stable, sharp and bright green emission. This enables spatial ordering of nanocubes ranging from micron to centimeter scale in thin films, which is crucial for advanced optoelectronic applications. To date, there is no report in literature on the anisotropic organization of perovskite CsPbBr3 nanocubes triggered by supramolecular co-assembly involving organogel nanofibers.
关键词： nanocubes,organogel,Shape control,hybrid materials,nanorods,cesium cholate,nanoplatelets,supramolecular co-assembly,colloidal CsPbBr3 perovskite NCs
更新于2025-09-12 10:27:22
-
Ultrapure Green Light-Emitting Diodes Based on CdSe/CdS Core/Crown Nanoplatelets
摘要： Colloidal nanoplatelets is a kind of two-dimensional nano-materials with an atomically flat surface, leading to an ultra-narrow emission linewidth of 8~12 nm. In this paper, we fabricated a green light-emitting diodes (LEDs) based on CdSe/CdS core/crown NPLs. This device exhibited an electroluminescence (EL) at 521 nm with a full-width at half maximum (FWHM) of 15 nm and a maximum luminance of 4684 cd/m2. Such narrow EL FWHM indicates that the core/crown NPLs can achieve an ultrapure green LED with a 124.7% of NTSC (National Televison System Committee), realizing a high color saturation and wide color gamut display.
关键词： Colloidal nanoplatelets,light-emitting diodes,color purity,wide color gamut display
更新于2025-09-11 14:15:04
-
Nanoplatelet modulation in 2D/3D perovskite targeting efficient light-emitting diodes
摘要： Light-emitting diodes (LEDs) based on two-dimensional (2D) perovskite nanoplatelets exhibit high electroluminescence (EL) efficiency because of the quantum confinement effect, which increases electron–hole recombination to promote radiative emission. It is well-known that a 2D nanoplatelet structure (?n? = 1) is detrimental for luminescence efficiency due to possible thermal quenching of excitons at room temperature. Here, a simple strategy is developed to suppress growth of NMA2PbBr4 (?n? = 1) nanoplatelets by carefully tuning the precursor ratio of cesium bromide (CsBr), formamidinium bromide (FABr) and 1-naphthylmethylammonium bromide (NMABr). The sub-domain size of the perovskite crystal decreases as the long-chain ligand NMABr ratio increases, leading to enhanced photoluminescence quantum yields (PLQY) due to size confinement effect when the NMABr ratio is below 60%. Unfortunately, the NMA2PbBr4 component in 2D/3D perovskites also grows with increasing NMABr ratio, which results in poor EL efficiency. FABr incorporation can provide additional control over suppression of NMA2PbBr4 growth in 2D/3D perovskites. A compact and uniform perovskite film with reduced NMA2PbBr4 content achieves PLQY of ～61%. Benefiting from these features, a green perovskite LED yields current efficiency of 46.8 cd A?1 with an external quantum efficiency of 14.9%. This study paves a new way to modulate the crystal structure in perovskites via a simple and effective method for high-performance LEDs.
关键词： light-emitting diodes,perovskite,quantum confinement,electroluminescence,nanoplatelets
更新于2025-09-11 14:15:04
-
AIP Conference Proceedings [Author(s) 6TH INTERNATIONAL CONFERENCE ON PRODUCTION, ENERGY AND RELIABILITY 2018: World Engineering Science & Technology Congress (ESTCON) - Kuala Lumpur, Malaysia (13–14 August 2018)] - Development of nanocomposites on the basis of graphene nanoplatelets
摘要： The prospects for using a phenol-formaldehyde resin (PFR) as a reactive surfactant in the preparation of highly concentrated dispersions of carbon nanostructured materials (up to 1 %) are considered in the present paper. Modifying graphene nanoplatelets (GNPs) with this surfactant promotes the effect of targeted self-assembly of carbon nanoparticles in solution (with decreasing pH), which makes it possible to obtain nanocomposites with improved properties. It is important that the use of highly concentrated dispersions of PFR-modified GNPs in the production of nanocomposite materials does not require a preliminary removal of the surfactant. Based on the resulting dispersion, the mesoporous carbon/GNPs composite with a developed surface (3000 ? 4000 m2 g?1) was successfully synthesized. It can be used as an electrode material for supercapacitors and an adsorbent of organic and inorganic species for wastewater treatment purposes.
关键词： graphene nanoplatelets,reactive surfactant,self-assembly,nanocomposites,mesoporous carbon,phenol-formaldehyde resin
更新于2025-09-10 09:29:36
-
Roll-to-Roll (R2R) Production of Ultrasensitive, Flexible, and Transparent Pressure Sensors Based on Vertically Aligned Lead Zirconate Titanate and Graphene Nanoplatelets
摘要： Despite extensive advances in the use of piezoelectric materials in flexible electronics, they have numerous shortcomings, including low efficiency, limited flexibility, and lack of transparency. Additionally, the production of these materials is often limited to small batch processes which are difficult to scale up for mass production. A novel method to produce ultrasensitive, high performance, flexible, and transparent piezoelectric materials where both lead zirconate titanate nanoparticles, and graphene nanoplatelets are aligned together in polydimethylsiloxane under an AC electric field in the thickness (“Z”) direction, is reported here for the first time. The electric field alignment improves the piezoelectric response along with transparency and also reduces the amount of filler required to achieve outstanding piezoelectric properties. The resulting ultrasensitive piezoelectric film is able to sense the pressure of a bird feather (1.4 mg) dropped from a certain distance, whereas at the touch of a fingertip, it can generate up to 8.2 V signal. Moreover, the mass production compatibility of the system is also demonstrated by producing a 3 m long and 15 cm wide large-area sample via a novel 44′ long roll-to-roll manufacturing line which is designed and developed by the group.
关键词： piezoelectric pressure sensor,flexible and transparent sensors,electric field–induced alignment,roll-to-roll manufacturing,PZT and graphene nanoplatelets
更新于2025-09-10 09:29:36
-
Green and Efficient Production of Boron Nitride Nanosheets via Oxygen Doping-Facilitated Liquid Exfoliation
摘要： As the structural analogue of graphene, boron nitride nanosheets (BNNSs) are anticipated to have a wide range of potential applications. BNNSs exhibit good mechanical properties, outstanding thermal conductivity, oxidation and chemical stability and are excellent electrical insulators. While BNNSs have gained recognition as one of the most versatile 2D materials in recent years, their application in research and industry is still hampered by the lack of methods to produce BNNSs in large quantity and a cost-effective way. In this study, we report highly efficient h-BN exfoliation via the oxygen doping-facilitated liquid exfoliation. Oxygen atoms are introduced into the hexagonal boron nitride (h-BN) structure via a facile thermal treatment. The relationship of thermal treatment, structural changes and h-BN exfoliation are studied to elucidate the key factor for advancing the BNNS production. The optimum concentration of hydroxyl groups and weakening of interlayer interactions have synergistically facilitated the delamination of h-BN in water under mild exfoliation conditions, resulting in up to 1255% yield increment and without noticeable new defects in the BNNS structure as compared with the untreated control. An efficient and environmentally friendly exfoliation process of h-BN is a crucial starting point towards the cost-effective and mass production of BNNSs which is needed for the currently identified and myriad future applications of BNNSs.
关键词： oxygen-doping,nanoplatelets,boron nitride nanosheets,2D nanomaterials
更新于2025-09-09 09:28:46
-
1T-Phase Tungsten Chalcogenides (WS <sub/>2</sub> , WSe <sub/>2</sub> , WTe <sub/>2</sub> ) Decorated with TiO <sub/>2</sub> Nanoplatelets with Enhanced Electron Transfer Activity for Biosensing Applications
摘要： Layered transition metal dichalcogenides (TMDs) have received a great deal of attention due to fact that they have varied band gap, depending on their metal/chalcogen composition and on the crystal structure. Furthermore, these materials demonstrate great potential application in a myriad of electrochemical technologies. Heterogeneous electron transfer (HET) abilities of TMD materials toward redox-active molecules occupy a key role in their suitability for electrochemical devices. Herein, we introduce a promising biosensing strategy based on improved heterogeneous electron transfer rate of WS2, WSe2, and WTe2 nanosheets exfoliated using tert-butyllithium (t-BuLi) and n-butyllithium (n-BuLi) intercalators decorated with vertically aligned TiO2 nanoplatelets. By comparison of all the nanohybrids, decoration of TiO2 on t-BuLi WS2 (TiO2@t-BuLi WS2) results in the fastest HET rate of 5.39 × 10?3 cm s?1 toward ferri/ferrocyanide redox couple. In addition, the implications of decorating tungsten dichalcogenides (WX2) with TiO2 nanoplatelets in enzymatic biosensor applications for H2O2 detection are explored. TiO2@t-BuLi WS2 outperforms all other nanohybrid counterparts and is demonstrated to be an outstanding sensing platform in enzyme-based biosensor with wide linear range, low detection limit, and high selectivity. Such conceptually new electrocatalytic detection systems shall find the way to the next generation biosensors.
关键词： heterogeneous electron transfer,H2O2 detection,nanosheets,TiO2 nanoplatelets,transition metal dichalcogenides
更新于2025-09-04 15:30:14