10468-30-1Relevant articles and documents
Mechanistic study of precursor evolution in colloidal group II-VI semiconductor nanocrystal synthesis
Liu, Haitao,Owen, Jonathan S.,Alivisatos, A. Paul
, p. 305 - 312 (2007)
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.
Improvement of CdSe quantum dot sensitized solar cells by surface modification of Cu2S nanocrystal counter electrodes
Park, Jeong-Hyun,Kang, Sung-Jin,Kim, Soojin,Lee, Hochun,Lee, Jong-Soo
, p. 51471 - 51476 (2014)
We report the improvement of a CdSe quantum-dot-sensitized solar cell (QDSSCs) based on surface modification of Cu2S nanoparticle counter-electrodes (CEs). In this work, we explored a low-cost, easy method to fabricate counter electrodes by direct deposition of colloidal Cu2S NCs on conducting FTO glass using drop casting or spin coating. The colloidal Cu2S NC films provide high surface area, which improves the catalytic activity for the redox couple and enhances the final photovoltaic performance. A CdSe QDSSC based on the 0.1 M EDT treated Cu2S CE/FTO shows a short-circuit current density (JSC) of 7.95 mA cm-2, a fill factor (FF) of 55.44%, and yielded a superior power conversion efficiency (η) of 2.1%, an improvement of 50% over that of the OA-capped Cu2S CE/FTO CE (1.4%). This journal is
CdSe@CdS Dot@Platelet Nanocrystals: Controlled Epitaxy, Monoexponential Decay of Two-Dimensional Exciton, and Nonblinking Photoluminescence of Single Nanocrystal
Wang, Yonghong,Pu, Chaodan,Lei, Hairui,Qin, Haiyan,Peng, Xiaogang
, p. 17617 - 17628 (2019)
Wurtzite CdSe@CdS dot@platelet nanocrystals, dot-shaped CdSe nanocrystals encased within epitaxially grown CdS nanoplatelets, are controllably synthesized with nearly monodisperse size and shape distribution and outstanding photoluminescence (PL) properties. The excellent size and shape control with their lateral to thickness dimension ratio up to 3:1 is achieved by systematically studying the synthetic parameters, which results in a simple, tunable, yet reproducible epitaxy scheme. These special types of core/shell nanocrystals possess two-dimensional emission dipoles with the ab plane of the wurtzite structure. While their near-unity PL quantum yield and monoexponential PL decay dynamics are at the same level of the state-of-art CdSe/CdS core/shell nanocrystals in dot shape, CdSe@CdS dot@platelet nanocrystals possess ～2 orders of magnitude lower probability for initiating PL blinking at the single-nanocrystal level than the dot-shaped counterparts do.
Ligand exchange and the stoichiometry of metal chalcogenide nanocrystals: Spectroscopic observation of facile metal-carboxylate displacement and binding
Anderson, Nicholas C.,Hendricks, Mark P.,Choi, Joshua J.,Owen, Jonathan S.
, p. 18536 - 18548 (2013)
We demonstrate that metal carboxylate complexes (L-M(O2CR) 2, R = oleyl, tetradecyl, M = Cd, Pb) are readily displaced from carboxylate-terminated ME nanocrystals (ME = CdSe, CdS, PbSe, PbS) by various Lewis bases (L = tri-n-butylamine, tetrahydrofuran, tetradecanol, N,N-dimethyl-n-butylamine, tri-n-butylphosphine, N,N,N′,N′- tetramethylbutylene-1,4-diamine, pyridine, N,N,N′,N′- tetramethylethylene-1,2-diamine, n-octylamine). The relative displacement potency is measured by 1H NMR spectroscopy and depends most strongly on geometric factors such as sterics and chelation, although also on the hard/soft match with the cadmium ion. The results suggest that ligands displace L-M(O2CR)2 by cooperatively complexing the displaced metal ion as well as the nanocrystal. Removal of up to 90% of surface-bound Cd(O 2CR)2 from CdSe and CdS nanocrystals decreases the Cd/Se ratio from 1.1 ± 0.06 to 1.0 ± 0.05, broadens the 1S e-2S3/2h absorption, and decreases the photoluminescence quantum yield (PLQY) from 10% to 2CR) 2 at room temperature (～60%) and fully reversed at elevated temperature. A model is proposed in which electron-accepting M(O 2CR)2 complexes (Z-type ligands) reversibly bind to nanocrystals, leading to a range of stoichiometries for a given core size. The results demonstrate that nanocrystals lack a single chemical formula, but are instead dynamic structures with concentration-dependent compositions. The importance of these findings to the synthesis and purification of nanocrystals as well as ligand exchange reactions is discussed.
Synthesis and Characterization of Ni2+-Doped CdSe and CdSe(S) Quantum Dots
Dotsenko, Anna S.,Dorofeev, Sergey G.,Znamenkov, Konstantin O.,Grigoriev, Denis V.
, p. 292 - 293 (2012)
The Ni-doped CdSe and CdSe(S) nanocrystals were synthesized using oleic and pelargic acids as stabilising agents and investigated by transmission electron microscopy, optical spectroscopy and inductively coupled plasma atomic emission spectroscopy.
Sulfur copolymer for the direct synthesis of ligand-free CdS nanoparticles
Martin, Trevor R.,Mazzio, Katherine A.,Hillhouse, Hugh W.,Luscombe, Christine K.
, p. 11244 - 11247 (2015)
Organic coordinating ligands are ubiquitously used to solubilize, stabilize and functionalize colloidal nanoparticles. Aliphatic organic ligands are typically used to control size during the nanoparticle growth period and are used as a high boiling point solvent for solution-based synthesis procedures. However, these aliphatic ligands are typically not well suited for the end use of the nanoparticles, so additional ligand exchange or ligand stripping procedures must be implemented after the nanoparticle synthesis. Herein we present a ligand-free CdS nanoparticle synthesis procedure using a unique sulfur copolymer. The sulfur copolymer is derived from elemental sulfur, which is a cheap and abundant material. This copolymer is used as a sulfur source and high boiling point solvent, which produces stabilized metal-sulfide nanoparticles that are suspended within a sulfur copolymer matrix. The copolymer can then be removed, thereby yielding ligand-free metal-sulfide nanoparticles.
Multistage Microfluidic Platform for the Continuous Synthesis of III–V Core/Shell Quantum Dots
Baek, Jinyoung,Shen, Yi,Lignos, Ioannis,Bawendi, Moungi G.,Jensen, Klavs F.
, p. 10915 - 10918 (2018)
We present a fully continuous chip microreactor-based multistage platform for the synthesis of quantum dots with heterostructures. The use of custom-designed chip reactors enables precise control of heating profiles and flow distribution across the microfluidic channels while conducting multistep reactions. The platform can be easily reconfigured by reconnecting the differently designed chip reactors allowing for screening of various reaction parameters during the synthesis of nanocrystals. III–V core/shell quantum dots are chosen as model reaction systems, including InP/ZnS, InP/ZnSe, InP/CdS and InAs/InP, which are prepared in flow using a maximum of six chip reactors in series.
Fragmentation of Magic-Size Cluster Precursor Compounds into Ultrasmall CdS Quantum Dots with Enhanced Particle Yield at Low Temperatures
Chen, Xiaoqin,Fan, Hongsong,Huang, Wen,Li, Lijia,Lu, Jiao,Rowell, Nelson,Wang, Shanling,Yu, Kui,Zhang, Chunchun,Zhang, Jing,Zhang, Meng
, p. 12013 - 12021 (2020)
Colloidal small-size CdS quantum dots (QDs) are produced usually with low particle yield, together with side products such as the particular precursor compounds (PCs) of magic-size clusters (MSC). Here, we report our synthesis of small-size CdS QDs without the coexistence of the PC and thus with enhanced particle yield. For a conventional reaction of cadmium oleate (Cd(OA)2) and sulfur (S) in 1-octadecene (ODE), we show that after the formation of the PC in the pre-nucleation stage, the addition of tri-n-octylphosphine oxide (TOPO) facilitates the production of small-size QDs. We demonstrate that TOPO fragmentizes the PC that have formed, which enables the nucleation and growth of small-size QDs even at room temperature. Our findings introduce a new approach to making small-size QDs without the coexistence of the PC and with improved particle yield. Providing experimental evidence for the two-pathway model proposed for the pre-nucleation stage of colloidal binary QDs, the present study aids in the advance of non-classical nucleation theory.
The formation mechanism of CdSe QDs through the thermolysis of Cd(oleate)2 and TOPSe in the presence of alkylamine
Kim, Taekeun,Jung, Yun Ku,Lee, Jin-Kyu
, p. 5593 - 5600 (2014)
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.
Scalable Synthesis of InAs Quantum Dots Mediated through Indium Redox Chemistry
Ginterseder, Matthias,Franke, Daniel,Perkinson, Collin F.,Wang, Lili,Hansen, Eric C.,Bawendi, Moungi G.
, p. 4088 - 4092 (2020)
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.
A Selective Cation Exchange Strategy for the Synthesis of Colloidal Yb3+-Doped Chalcogenide Nanocrystals with Strong Broadband Visible Absorption and Long-Lived Near-Infrared Emission
Creutz, Sidney E.,Fainblat, Rachel,Kim, Younghwan,De Siena, Michael C.,Gamelin, Daniel R.
, p. 11814 - 11824 (2017)
Doping lanthanide ions into colloidal semiconductor nanocrystals is a promising strategy for combining their sharp and efficient 4f-4f emission with the strong broadband absorption and low-phonon-energy crystalline environment of semiconductors to make new solution-processable spectral-conversion nanophosphors, but synthesis of this class of materials has proven extraordinarily challenging because of fundamental chemical incompatibilities between lanthanides and most intermediate-gap semiconductors. Here, we present a new strategy for accessing lanthanide-doped visible-light-absorbing semiconductor nanocrystals by demonstrating selective cation exchange to convert precursor Yb3+-doped NaInS2 nanocrystals into Yb3+-doped PbIn2S4 nanocrystals. Excitation spectra and time-resolved photoluminescence measurements confirm that Yb3+ is both incorporated within the PbIn2S4 nanocrystals and sensitized by visible-light photoexcitation of these nanocrystals. This combination of strong broadband visible absorption, sharp near-infrared emission, and long (>400 μs) emission lifetimes in a colloidal nanocrystal system opens promising new opportunities for both fundamental-science and next-generation spectral-conversion applications such as luminescent solar concentrators.
Cation Exchange Induced Transformation of InP Magic-Sized Clusters
Stein, Jennifer L.,Steimle, Molly I.,Terban, Maxwell W.,Petrone, Alessio,Billinge, Simon J. L.,Li, Xiaosong,Cossairt, Brandi M.
, p. 7984 - 7992 (2017)
Magic-sized clusters (MSCs) can provide valuable insight into the atomically precise progression of semiconductor nanocrystal transformations. We report the conversion of an InP MSC to a Cd3P2 MSC through a cation exchange mechanism and attempt to shed light on the evolution of the physical and electronic structure of the clusters during the transformation. Utilizing a combination of spectroscopic (NMR/UV-vis) and structural characterization (ICP-OES/MS/PXRD/XPS/PDF) tools, we demonstrate retention of the original InP MSC crystal lattice as Z-type ligand exchange initially occurs. Further cation exchange induces lattice relaxation and a significant structural rearrangement. These observations contrast with reports of cation exchange in InP quantum dots, indicating unique reactivity of the InP MSC.
