- Room-Temperature Formation Pathway for CdTeSe Alloy Magic-Size Clusters
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Little is known about the pathway of room-temperature formation of ternary CdTeSe magic-size clusters (MSCs) obtained by mixing binary CdTe and CdSe induction period samples containing binary precursor compounds (PCs) of MSCs, monomers (Ms), and fragments (Fs). Also, unestablished are dispersion effects that occur when as-mixed samples (without incubation) are placed in toluene (Tol) and octylamine (OTA) mixtures. The resulting ternary MSCs, exhibiting a sharp optical absorption peak at 399 nm, are labelled CdTeSe MSC-399, and their PCs are referred to as CdTeSe PC-399. When the amount of OTA is relatively small, single-ensemble MSC-399 evolved without either binary CdTe or CdSe MSCs. When the OTA amount is relatively large, CdTe MSC-371 appeared initially and then disappeared, while single-ensemble MSC-399 developed more deliberately. The larger the OTA amount, the more slowly these changes proceeded. The substitution reaction of CdTe PC + CdSe M/F?CdTeSe PC-399 + CdTe M/F is proposed to be rate-determining for the MSC-399 formation in a Tol and OTA mixture. This study provides further understanding of the transformation pathway between MSCs.
- Chen, Meng,Chen, Xiaoqin,Fan, Hongsong,Gao, Dong,Huang, Wen,Luan, Chaoran,Rowell, Nelson,Willis, Maureen,Yu, Kui,Zeng, Jianrong,Zhang, Hai,Zhang, Meng
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Read Online
- Controllable synthesis and growth mechanism of dual size distributed PbSe quantum dots
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To understand the fundamental science of nanocrystal growth, the controllable synthesis and growth mechanism of dual size distributed PbSe quantum dots (QDs) are studied. The characterizations of high-resolution transmission electron microscopy (HR-TEM) and photoluminescence (PL) unambiguously demonstrate the dual size distribution of PbSe QDs. Thermodynamic stability of small QDs is confirmed by a controllable synthesis of temperature variation and kinetic perturbation with successive injection of precursors, suggesting a possible mechanism that a chemical-potential well may lead to the size separation. The control of growth temperature plays an important role in the realization of dual size distributed PbSe QDs. Further study of temporal evolution demonstrates the size refocusing of QDs at a higher temperature. Both kinetic perturbation and thermodynamic perturbation could facilitate QDs to overcome the potential barrier. Understanding this mechanism is of significance for the controllable synthesis and applications of PbSe QDs. This journal is
- Li, Ruifeng,Ye, Zhenyu,Kong, Weiguang,Wu, Huizhen,Lin, Xing,Fang, Wei
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Read Online
- Microwave-assisted synthesis method for rapid synthesis of tin selenide electrode material for supercapacitors
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As an important binary IV-VI semiconductor compound, tin selenide (SnSe) has been investigated intensively for a wide range of applications in energy storage and photovoltaic devices, due to its unique electronic and optoelectronic properties. In this work, we successfully synthesized SnSe powders by a simple, rapid and high-yield method called microwave-assisted synthesis for the first time and also measured their electrochemical performances. By rationally controlling the microwave heating time, we found that the 15-min reacted sample exhibited the most outstanding specific capacitance and rate capability (214.3 F/g at 1 A/g and 182.8 F/g at 20 A/g), and excellent cycling stability. The microwave-assisted synthesis method is efficient and rapid for preparing SnSe electrode materials.
- Ni, Dan,Chen, Yuanxun,Yang, Xiaowei,Liu, Congcong,Cai, Kefeng
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Read Online
- Active Regulation of Supramolecular Chirality through Integration of CdSe/CdS Nanorods for Strong and Tunable Circular Polarized Luminescence
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Building the cooperativity in artificial self-assembling systems will synergistically reshape their properties and expand their application spectrum. Here, we show how the cooperativity between achiral CdSe/CdS nanorods (NRs) and chiral perylene diimide (
- Liu, Rongjuan,Feng, Zhenyu,Cheng, Caikun,Li, Hui,Liu, Jiaming,Wei, Jingjing,Yang, Zhijie
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supporting information
p. 2333 - 2342
(2022/02/10)
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- Scalable Synthesis of InAs Quantum Dots Mediated through Indium Redox Chemistry
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Next-generation optoelectronic applications centered in the near-infrared (NIR) and short-wave infrared (SWIR) wavelength regimes require high-quality materials. Among these materials, colloidal InAs quantum dots (QDs) stand out as an infrared-active candidate material for biological imaging, lighting, and sensing applications. Despite significant development of their optical properties, the synthesis of InAs QDs still routinely relies on hazardous, commercially unavailable precursors. Herein, we describe a straightforward single hot injection procedure revolving around In(I)Cl as the key precursor. Acting as a simultaneous reducing agent and In source, In(I)Cl smoothly reacts with a tris(amino)arsenic precursor to yield colloidal InAs quantitatively and at gram scale. Tuning the reaction temperature produces InAs cores with a first excitonic absorption feature in the range of 700-1400 nm. A dynamic disproportionation equilibrium between In(I), In metal, and In(III) opens up additional flexibility in precursor selection. CdSe shell growth on the produced cores enhances their optical properties, furnishing particles with center emission wavelengths between 1000 and 1500 nm and narrow photoluminescence full-width at half-maximum (FWHM) of about 120 meV throughout. The simplicity, scalability, and tunability of the disclosed precursor platform are anticipated to inspire further research on In-based colloidal QDs.
- Ginterseder, Matthias,Franke, Daniel,Perkinson, Collin F.,Wang, Lili,Hansen, Eric C.,Bawendi, Moungi G.
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supporting information
p. 4088 - 4092
(2020/03/04)
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- General and Efficient C-C Bond Forming Photoredox Catalysis with Semiconductor Quantum Dots
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Photoredox catalysis has become an essential tool in organic synthesis because it enables new routes to important molecules. However, the best available molecular catalysts suffer from high catalyst loadings and rely on precious metals. Here we show that colloidal nanocrystal quantum dots (QDs) can serve as efficient and robust, precious-metal free, photoassisted redox catalysts. A single-sized CdSe quantum dot (3.0 ± 0.2 nm) can replace several different dye catalysts needed for five different photoredox reactions (β-alkylation, β-aminoalkylation, dehalogenation, amine arylation, and decarboxylative radical formation). Even without optimization of the QDs or the reaction conditions, efficiencies rivaling those of the best available metal dyes were obtained.
- Caputo, Jill A.,Frenette, Leah C.,Zhao, Norman,Sowers, Kelly L.,Krauss, Todd D.,Weix, Daniel J.
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supporting information
p. 4250 - 4253
(2017/04/03)
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- Dissolution behaviour and activation of selenium in phosphonium based ionic liquids
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The dissolution behaviour of grey selenium in phosphonium based ionic liquids (ILs) has been investigated for the first time by 31P and 77Se nuclear magnetic resonance (NMR) experiments. The investigations evidence the formation of trialkylphosphane selenides which can serve as a selenium reservoir in the subsequent formation of metal selenides.
- Zhang, Tao,Schwedtmann, Kai,Weigand, Jan J.,Doert, Thomas,Ruck, Michael
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p. 7588 - 7591
(2017/07/12)
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- Mechanistic insights into the role of alkylamine in the synthesis of CdSe nanocrystals
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This paper reports a detailed mechanistic study of the effect of alkylamine on the synthesis of CdSe nanocrystals. Alkylamines are one of the most important additives for the synthesis of colloidal semiconductor nanocrystals. However, their effect on the monomer production as well as nanocrystal nucleation and growth are not well understood, as indicted by inconsistent and contradictory conclusions in the literature. We found that alkylamines slow down the reaction between cadmium oleate and trialkyl phosphine selenide by binding to cadmium and preventing the activation of trialkyl phosphine selenide. A linear correlation was observed between the observed reaction rate constant and the 31P NMR chemical shift or 1JP-Se of phosphine selenide. In the presence of alkylamine, an alkylaminophosphonium intermediate was observed. Mechanistic study suggests that the cleavage of Pi -Se bond is through nucleophilic attack by carboxylate instead of alkylamine. Interestingly, although alkylamines decrease the rate of monomer production, it increases the rate of CdSe nanocrystal growth. Although seemingly contradictory, this is due to a drastic decrease in the nanocrystal nucleation events in the presence of alkylamines. As a result, each nucleus is fed with more monomers and grows faster in the presence of alkylamine than in its absence.
- Garcia-Rodriguez, Raul,Liu, Haitao
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p. 1968 - 1975
(2014/03/21)
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- The formation mechanism of CdSe QDs through the thermolysis of Cd(oleate)2 and TOPSe in the presence of alkylamine
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The thermal decomposition of Cd(oleate)2, a metal organocarboxylate complex, in the presence of alkylamine was studied in order to understand the formation mechanism of CdSe nanocrystals (quantum dots, QDs) in the hot-injection method. The major intermediates and side products were characterized by nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that the nucleophilic attack of the metal-coordinated amine toward the most electron-deficient carbonyl carbon of the oleate ligands initiated decomposition to generate a CdO cluster (or oligomer). Based on our experimental results, we proposed a two-step formation mechanism of CdSe QDs involving the formation of CdO intermediates with alkylamines playing a critical role as nucleophiles in the thermolysis process, followed by a metathesis reaction with trioctylphosphine selenide (TOPSe) as a chalcogenide source. This journal is the Partner Organisations 2014.
- Kim, Taekeun,Jung, Yun Ku,Lee, Jin-Kyu
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p. 5593 - 5600
(2014/07/08)
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- Mysteries of TOPSe revealed: Insights into quantum dot nucleation
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We have investigated the reaction mechanism responsible for QD nucleation using optical absorption and nuclear magnetic resonance spectroscopies. For typical II-VI and IV-VI quantum dot (QD) syntheses, pure tertiary phosphine selenide sources (e.g., trioctylphosphine selenide (TOPSe)) were surprisingly found to be unreactive with metal carboxylates and incapable of yielding QDs. Rather, small quantities of secondary phosphines, which are impurities in tertiary phosphines, are entirely responsible for the nucleation of QDs; their low concentrations account for poor synthetic conversion yields. QD yields increase to nearly quantitative levels when replacing TOPSe with a stoiciometric amount of a secondary phosphine chalcogenide such as diphenylphosphine selenide. Based on our observations, we have proposed potential monomer identities, reaction pathways, and transition states and believe this mechanism to be universal to all II-VI and IV-VI QDs synthesized using phosphine based methods.
- Evans, Christopher M.,Evans, Meagan E.,Krauss, Todd D.
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supporting information; experimental part
p. 10973 - 10975
(2010/09/17)
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- Precursor conversion kinetics and the nucleation of cadmium selenide nanocrystals
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The kinetics of cadmium selenide (CdSe) nanocrystal formation was studied using UV-visible absorption spectroscopy integrated with an automated, high-throughput synthesis platform. Reaction of anhydrous cadmium octadecylphosphonate (Cd-ODPA) with alkylphosphine selenides (1, tri-n-octylphosphine selenide; 2, di-n-butylphenylphosphine selenide; 3, n-butyldiphenylphosphine selenide) in recrystallized tri-n-octylphosphine oxide was monitored by following the absorbance of CdSe at λ = 350 nm, where the extinction coefficient is independent of size, and the disappearance of the selenium precursor using {1H}31P NMR spectroscopy. Our results indicate that precursor conversion limits the rate of nanocrystal nucleation and growth. The initial precursor conversion rate (Qo) depends linearly on [1] (Qo(1) = 3.0-36 μM/s) and decreases as the number of aryl groups bound to phosphorus increases (1 > 2 > 3). Changes to Qo influence the final number of nanocrystals and thus control particle size. Using similar methods, we show that changing [ODPA] has a negligible influence on precursor reactivity while increasing the growth rate of nuclei, thereby decreasing the final number of nanocrystals. These results are interpreted in light of a mechanism where the precursors react in an irreversible step that supplies the reaction medium with a solute form of the semiconductor.
- Owen, Jonathan S.,Chan, Emory M.,Liu, Haitao,Alivisatos, A. Paul
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experimental part
p. 18206 - 18213
(2011/03/21)
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- Mechanistic study of precursor evolution in colloidal group II-VI semiconductor nanocrystal synthesis
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The molecular mechanism of precursor evolution in the synthesis of colloidal group II-VI semiconductor nanocrystals was studied using 1H, 13C, and 31P NMR spectroscopy and mass spectrometry. Tri-n-butylphosphine chalcogenides (TBPE; E = S, Se, Te) react with an oleic acid complex of cadmium or zinc (M-OA; M = Zn, Cd) in a noncoordinating solvent (octadecene (ODE), n-nonane-d20, or n-decane-d22), affording ME nanocrystals, tri-n-butylphosphine oxide (TBPO), and oleic acid anhydride ((OA)2O). Likewise, the reaction between trialkylphosphine selenide and cadmium n-octadecylphosphonic acid complex (Cd-ODPA) in tri-n-octylphosphine oxide (TOPO) produces CdSe nanocrystals, trialkylphosphine oxide, and anhydrides of n-octadecylphosphonic acid. The disappearance of tri-n-octylphosphine selenide in the presence of Cd-OA and Cd-ODPA can be fit to a single-exponential decay (kobs = (1.30 ± 0.08) × 10-3 s-1, Cd-ODPA, 260 °C, and kobs = (1.51 ± 0.04) × 10-3 s-1, Cd-OA, 117 °C). The reaction approaches completion at 70-80% conversion of TOPSe under anhydrous conditions and 100% conversion in the presence of added water. Activation parameters for the reaction between TBPSe and Cd-OA in n-nonane-d20 were determined from the temperature dependence of the TBPSe decay over the range of 358-400 K (ΔH? = 62.0 ± 2.8 kJ·mol-1, ΔS? = -145 ± 8 J·mol-1·K-1). A reaction mechanism is proposed where trialkylphsophine chalcogenides deoxygenate the oleic acid or phosphonic acid surfactant to generate trialkylphosphine oxide and oleic or phosphonic acid anhydride products. Results from kinetics experiments suggest that cleavage of the phosphorus chalcogenide double bond (TOP=E) proceeds by the nucleophilic attack of phosphonate or oleate on a (TOP=E)-M complex, generating the initial M-E bond.
- Liu, Haitao,Owen, Jonathan S.,Alivisatos, A. Paul
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p. 305 - 312
(2008/04/18)
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- Agents for use in magnetic resonance and optical imaging
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Semiconductor nanoparticles are doped with paramagnetic ions to serve as dual-mode optical and magnetic resonance imaging (MRI) contrast agents. These nanoparticles can be constructed in smaller diameters than typical MRI agents. The dual-modality nature allows the particles to be used for in vivo imaging by MRI, and then followed by histology with optical imaging techniques.
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