Family 373 and 406 of CdS magic-sized nanocrystals （MSNCs） were synthesized by a one-pot non-injection approach and white-light emission was generated from the coexistence of them. This light had excellent color cha...Family 373 and 406 of CdS magic-sized nanocrystals （MSNCs） were synthesized by a one-pot non-injection approach and white-light emission was generated from the coexistence of them. This light had excellent color characteristics, as defined by their pure white CIE （Commission International de l＇Eclairage） color coordinates （0.328, 0.343）, and it correlated with a color temperature of 5696 K. A probable thermodynamic equilibrium was proposed to explain the white-light emission behavior in this letter.展开更多
Semiconductor magic-sized nanoclusters have got tremendous interests owing to their distinct chemical and photophysical properties,however,researches concerning their applications are still quite limited.Herein,we emp...Semiconductor magic-sized nanoclusters have got tremendous interests owing to their distinct chemical and photophysical properties,however,researches concerning their applications are still quite limited.Herein,we employ magic-sized CdSe nanoclusters as the light absorber for hydrogen photogeneration,which exhibits much better photocatalytic performance as compared to other conventional semiconductor quantum dots,such as CdS,CdSe,CdS/CdSe,and CdSe/CdS under identical conditions.Photoluminescence lifetime and transient absorption studies indicated that the superior activity is mainly ascribed to the longer exciton lifetime and fast electron transfer from nanoclusters to cocatalyst.Moreover,the issue of instability during reaction could be significantly inhibited by anchoring Zn2+onto the surface of nanoclusters,which gives the average efficacy of hydrogen evolution at 0.61±0.07 mL·h^(-1)·mgcatalyst^(-1),i.e.,27.3±2.9 mmol·h^(-1)·g_(catalyst)^(-1)(420 nm)with maintained 95.2%of original activity over 12 h illumination.展开更多
Precursor compounds(PCs)link quantum dots(QDs)and magic-sized clusters(MSCs),which is pivotal in the conversion between QDs and MSCs.Here,for the first time,we report the transformation,synthesis,and composition of a ...Precursor compounds(PCs)link quantum dots(QDs)and magic-sized clusters(MSCs),which is pivotal in the conversion between QDs and MSCs.Here,for the first time,we report the transformation,synthesis,and composition of a type of ZnSe PCs.ZnSe PCs can be directly transformed to two different MSCs with the assistance of octylamine and acetic acid at room temperature.The two types of MSCs exhibit sharp absorption peaks at 299 and 328 nm which are denoted as MSC-299 and MSC-328.In the preparation of ZnSe PCs,diphenylphosphine(DPP)as an additive plays a key role which not only inhibits the thermal decomposition of Zn precursor,but also acts as a reducing agent to reduce the by-products produced in the reaction.The composition was explored by X-ray photoelectron spectroscopy,energy dispersive spectrometer,matrix-assisted laser desorption/ionization time-of-flight mass spectra with ZnSe PC powder appeared as white powder after purifying by toluene(Tol)and methanol(MeOH).The results indicate that the molar ratio of Zn/Se is 2:1 with a molecular of〜3,350 Da.Therefore,we propose that the molecular formula of ZnSe PCs is Zn_(32)Se_(16).In addition,at the molecular level,the covalent bond of Zn-Se is formed in ZnSe PCs.This study offers a deeper understanding of the transformation from PCs to MSCs and for the first time proposes the composition of PCs.Meanwhile,this research provides us with a new understanding of the role of DPP in the synthesis of colloidal semiconductor nanoparticles.展开更多
Cadmium selenide(CdSe)is a model system that has been widely used to study the synthesis of semiconductor magic-size clusters(MSCs)and quantum dots(QDs),together with their formation pathways,optical properties,and qu...Cadmium selenide(CdSe)is a model system that has been widely used to study the synthesis of semiconductor magic-size clusters(MSCs)and quantum dots(QDs),together with their formation pathways,optical properties,and quantum confinement effects.Here,we show the occurrence of MSC-330,MSC-360,MSC-390,and MSC-415 from a prenucleation-stage sample of CdSe in dispersion at temperatures much lower than the sample preparation temperature.The number represents the lowest energy peak in nanometers of optical absorption.We develop a model based on prenucleation clusters(PNCs)to explain and rationalize our experimental data,and propose that the MSCs are a group of isomers emerging from their corresponding precursor compounds(PCs).The PNC-MSC-415 isomerization is driven thermodynamically,with the loss in∆H∆Senthalpy(<0)and entropy(<0).With that,we introduce a PNC-based approach to control the MSC development in dispersion,and provide compelling evidence for the existence of the PNC and of two categories of MSCs displaying either absorption singlets or doublets.展开更多
Isosbestic behavior has been traditionally deemed as a spectroscopic indicator of a chemical reaction,in which a reactant transforms directly to a product without intermediates.Room-temperature transformations of coll...Isosbestic behavior has been traditionally deemed as a spectroscopic indicator of a chemical reaction,in which a reactant transforms directly to a product without intermediates.Room-temperature transformations of colloidal semiconductor magic-size clusters(MSCs)from MSC-a to MSC-b display interrupted spectral shifts in optical absorption with or without isosbestic behavior.We demonstrate that a multicomponent model explains consistently the pathway.The model invokes precursor compounds(PCs)of MSCs as intermediates,with three key steps from MSC-a to PC-a(step 1),to PC-b(step 2),and to MSC-b(step 3).Monomer substitution assists step 2(PC-a to PC-b).Based on the experimental result and theoretical study,we conclude that when step 1 or 2 or 3 is rate-determining,isosbestic behavior can be ideally perfect or distorted or absent,respectively.Our study provides a deeper understanding of isosbestic behavior and of MSC transformations that are assisted by PC intermediates and monomer substitution.展开更多
Little is known about the room-temperature formation of colloidal semiconductor magic-size clusters(MSCs)of II-VI ternary CdE1E2 from ZnE1E2.Here,we report the first synthesis of CdTeSe MSCs from ZnTeSe MSC-340(displa...Little is known about the room-temperature formation of colloidal semiconductor magic-size clusters(MSCs)of II-VI ternary CdE1E2 from ZnE1E2.Here,we report the first synthesis of CdTeSe MSCs from ZnTeSe MSC-340(displaying a sharp optical absorption peaking at 340 nm)at room temperature.When ZnTeSe MSC-340 and Cd(OAc)2/OLA(made from cadmium acetate and oleylamine)were mixed,the former disappeared,while CdTeSe MSC-422 and/or MSC-399 developed.Based on our experimental data,we propose that the conversion proceeds via the interaction of Cd(OAc)2/OLA and the precursor compound of ZnTeSe MSC-340,PC-340.As such,ZnTeSe MSC-340 first isomerized to PC-340;via cation exchange PC-340 transformed to CdTeSe PCs.In turn,the resultant CdTeSe PC isomerized to CdTeSe MSCs,the process of which was rate-determining.Furthermore,we show that the transformation between CdTeSe MSC-422 and MSC-399 was reversible,providing strong evidence that they are a pair of isomers.Our study introduces a room-temperature avenue towards Cd-based MSCs from Zn-based ones,which follows anionic framework conservation and anionic number conservation.展开更多
Little is known about the synthesis of colloidal ternary semiconductor magic-size clusters(MSCs)and quantum dots(QDs)in an aqueous environment.We report here the first synthesis of aqueous-phase CdSeS MSC-380(displayi...Little is known about the synthesis of colloidal ternary semiconductor magic-size clusters(MSCs)and quantum dots(QDs)in an aqueous environment.We report here the first synthesis of aqueous-phase CdSeS MSC-380(displaying sharp optical absorption peaking at~380 nm)at room temperature and QDs at elevated temperatures.The reaction contains CdCl2·2.5H_(2)O,3-mercaptopropionic acid(MPA,HS-(CH_(2))2-COOH),selenourea(SeU,NH_(2)-C(Se)-NH_(2)),and thioacetamide(TAA,CH3-C(S)-NH_(2)).Prior to the nucleation and growth(N/G)of QDs,there are clusters formed at 25℃.The prenucleation-stage clusters are the precursor compound of CdSeS MSC-380(PC-380).The PC is relatively transparent in optical absorption;in the presence of a primary amine butylamine(BTA,CH3-(CH_(2))3-NH_(2)),the PC transforms to absorbing CdSeS MSC-380.At 80℃,the PC decreases and the N/G of CdSeS QDs appears.The present study paves the way to the aqueous-phase synthesis of ternary CdSeS MSCs and QDs,providing an in-depth understanding of the cluster formation in the prenucleation stage of CdSeS QDs.展开更多
The formation pathway of colloidal semiconductor ZnSe magic-size clusters(MSCs)in a reaction that display an optical absorption doublet remains poorly understood.The reaction of Zn(OAc)_(2)/OLA(made from zinc acetate ...The formation pathway of colloidal semiconductor ZnSe magic-size clusters(MSCs)in a reaction that display an optical absorption doublet remains poorly understood.The reaction of Zn(OAc)_(2)/OLA(made from zinc acetate and oleylamine)and tri-noctylphosphine selenide(SeTOP)in OLA in the presence of diphenylphosphine(HPPh_(2))is studied,in which dMSC-345 displays a doublet peaking at 328/345 nm.We suggest that the development is from the clusters that form in the initial prenucleation stage of the reaction.The clusters are the precursor compound(PC-299)of MSC-299(displaying an absorption singlet peaking at 299 nm).PC-299 transforms to PC-345 at a later stage.The presence of alcohol(such as methanol or ethylene glycol)promotes another pathway,which is the PC-299 to PC-320 transformation.PC-320 transforms to dMSC-320(with a doublet at 305/320 nm),followed by dMSC-345 via PC-345.The present study provides additional evidence that clusters(PC-299)form and transform(such as to dMSC-345 via PC-345)in the prenucleation stage of ZnSe quantum dots(QDs).展开更多
The formation pathway of aqueous-phase colloidal semiconductor magic-size clusters(MSCs)remains unrevealed.In the present work,we demonstrate,for the first time,a precursor compound(PC)-enabled formation pathway of aq...The formation pathway of aqueous-phase colloidal semiconductor magic-size clusters(MSCs)remains unrevealed.In the present work,we demonstrate,for the first time,a precursor compound(PC)-enabled formation pathway of aqueous-phase CdSe MSCs exhibiting a sharp absorption peaking at about 420 nm(MSC-420).The CdSe MSC-420 is synthesized with CdCl2 and selenourea as the respective Cd and Se sources,and with 3-mercaptopropionic acid or L-cysteine as a ligand.Absorption featureless CdSe PCs form first in the aqueous reaction batches,which transform to MSC-420 in the presence of primary amines.The coordination between primary amine and Cd^(2+)on PCs may be responsible to the PC-to-MSC transformation.Upon increasing the reactant concentrations or decreasing the CdCl_(2)-ligand feed molar ratios,the Cd precursor self-assembles into large aggregates,which may encapsulate the resulting CdSe PCs and inhibit their transformation to MSC-420.The present study sheds essential light on the syntheses and formation mechanisms of nanocrystals.展开更多
We report,for the first time,the synthesis of CdS magic-size clusters (MSCs) which exhibit a single sharp absorption peaking at ~ 361 nm,along with sharp band edge photoemission at ~ 377 nm and broad trap emission pea...We report,for the first time,the synthesis of CdS magic-size clusters (MSCs) which exhibit a single sharp absorption peaking at ~ 361 nm,along with sharp band edge photoemission at ~ 377 nm and broad trap emission peaking at ~ 490 nm.These MSCs are produced in a singleensemble form without the contamination of conventional quantum dots (QDs) and/or other-bandgap clusters.They are denoted as MSC-361.We present the details of several controlled syntheses done in oleylamine (OLA),using C,d(NO3)2 or C,d(OAc)2 as a C,d source and thioacetamide (TAA) or elementary sulfur (S) as a S source.A high synthetic reproducibility of the reaction of Cd(NO3)2 and TAA to single-ensemble MSC-361 is achieved,the product of which is not contaminated by other bandgap clusters and/or QDs.In some cases,the reaction product exhibits an additional absorption peak at ~ 322 nm.We demonstrate that the two peaks,at 361 and 322 nm,do not evolve synchronously.Therefore,the 322 nm peak is not a higher order electronic transition of MSC-361,but due to the presence of another ensemble,namely MSC-322.The present study suggests that there is an outstanding need for the development of a physical model to narrow the knowledge gap regarding the electronic structure in these colloidal semiconductor CdS MSCs.展开更多
Little is known about how to precisely promote the selective production of either colloidal semiconductor metal chalcogenide(ME),magic-size clusters(MSCs),or quantum dots(QDs).Recently,a two-pathway model has been pro...Little is known about how to precisely promote the selective production of either colloidal semiconductor metal chalcogenide(ME),magic-size clusters(MSCs),or quantum dots(QDs).Recently,a two-pathway model has been proposed to comprehend their evolution;here,we reveal for the first time that the size of precursors plays a decisive role in the selected evolution pathway of MSCs and QDs.With the reaction of cadmium myristate(Cd(MA)2)and tri-n-octylphosphine selenide(SeTOP)in 1-octadecene(ODE)as a model system,the size of Cd precursors was manipulated by the steric hindrance of carboxylic acid(RCOOH)additive.Without RCOOH,the reaction produced both CdSe MSCs and QDs(from 100 to 240℃).With RCOOH,the reaction produced MSCs or QDs when R was small(such as CH3−)or large(such as C6H5−),respectively.According to the twopathway model,the selective evolution is attributed to the promotion and suppression of the self-assembly of Cd and Se precursors,respectively.We propose that the addition of carboxylic acid may occur ligand exchange with Cd(MA)2,causing the different sizes of Cd precursor.The results suggest that the size of Cd precursors regulates the self-assemble behavior of the precursors,which dictates the directed evolution of either MSCs or QDs.The present findings bring insights into the two-pathway model,as the size of M and E precursors determine the evolution pathways of MSCs or QDs,the understanding of which is of great fundamental significance toward mechanism-enabled design and predictive synthesis of functional nanomaterials.展开更多
Achieving nanoconfinement-controlled synthesis of nanoplatelets(NPLs)via solution process under ambient condition remains a challenge.In this work,we developed a general ligand-induced strategy to synthesize colloidal...Achieving nanoconfinement-controlled synthesis of nanoplatelets(NPLs)via solution process under ambient condition remains a challenge.In this work,we developed a general ligand-induced strategy to synthesize colloidal stable all-inorganic semiconductor NPLs with controllable lateral dimensions.By introducing certain metal salts(cations:Zn^(2+)and In^(3+),anions:NO_(3)^(−),BF_(4)^(−),or triflate OTf−),wurtzite-structured(WZ-)CdS,CdSe,CdTe,and alloy Cd1−xZnxSe NPLs were directly synthesized in solution through the controlled diffusion of magic-size clusters(MSCs)at room temperature.Mechanism studies revealed that destabilization of MSCs and nanoconfined growth in templates facilitated the formation of NPLs.The present study not only provides a new synthetic route for the preparation of NPLs but also helps to provide insight into their probable formation mechanism and presents an important advance toward the rational design of functional nanomaterials.展开更多
Both semiconductor nanocrystals and organic molecules are important photofunctional materials for an array of applications.It is interesting to examine the intermediate regime between these two families,which can be i...Both semiconductor nanocrystals and organic molecules are important photofunctional materials for an array of applications.It is interesting to examine the intermediate regime between these two families,which can be interpreted as the strong-confinement limit of the nanocrystals or alternatively as the large-size limit of molecules.Here,we choose Cd_(3)P_(2) magic-size clusters(MSCs)as a unique platform and apply time-resolved spectroscopy to investigate their spectral and dynamic properties.We find that these small clusters display molecular-like vibronic progression on their absorption and emission spectra and a large Stokes shift,which leads to well-separated transient absorption bleach and stimulated emission signals distinct from typical nanocrystals.On the other hand,such small size MSCs can still accommodate biexciton states,and the strongly enhanced Coulombic interactions lead to very fast dephasing of the biexciton resonance as well as rapid biexciton Auger annihilation(1.5 ps).Further,temperature-dependent measurements provide evidence for the transformation of band-edge excitons to localized excitons,with the localization likely driven by the softened lattice in these small-size clusters.These collective results demonstrate that strongly-confined nanoclusters indeed bridge the gap between nanocrystals and molecules,and can be a unique library to search for exotic excited state properties.展开更多
Magic-sized(CdSe)_(13) clusters(MSCs)represent a material class at the boundary between molecules and quantum dots that exhibit a pronounced and well separated excitonic fine structure.The characteristic photoluminesc...Magic-sized(CdSe)_(13) clusters(MSCs)represent a material class at the boundary between molecules and quantum dots that exhibit a pronounced and well separated excitonic fine structure.The characteristic photoluminescence is composed of exciton bandgap emission and a spectrally broad mid-gap emission related to surface defects.Here,we report on a thermally activated energy transfer from fine-structure split exciton states to surface states by using temperature dependent photoluminescence excitation spectroscopy.We demonstrate that the broad mid-gap emission can be suppressed by a targeted Mn-doping of the MSC leading to the characteristic orange luminescence of the^(4)T_(1)→^(6)A_(1)Mn^(2+)transition.The energy transfer to the Mn^(2+)states is found to be significantly different than the transfer to the surface defect states,as the activation of the dopant emission requires a spin-conserving charge carrier transfer that only dark excitons can provide.展开更多
文摘Family 373 and 406 of CdS magic-sized nanocrystals （MSNCs） were synthesized by a one-pot non-injection approach and white-light emission was generated from the coexistence of them. This light had excellent color characteristics, as defined by their pure white CIE （Commission International de l＇Eclairage） color coordinates （0.328, 0.343）, and it correlated with a color temperature of 5696 K. A probable thermodynamic equilibrium was proposed to explain the white-light emission behavior in this letter.
基金This work was supported by the National Natural Science Foundation of China(No.21675146)the National Key Research and Development Program of China(No.2016YFA0201300).
文摘Semiconductor magic-sized nanoclusters have got tremendous interests owing to their distinct chemical and photophysical properties,however,researches concerning their applications are still quite limited.Herein,we employ magic-sized CdSe nanoclusters as the light absorber for hydrogen photogeneration,which exhibits much better photocatalytic performance as compared to other conventional semiconductor quantum dots,such as CdS,CdSe,CdS/CdSe,and CdSe/CdS under identical conditions.Photoluminescence lifetime and transient absorption studies indicated that the superior activity is mainly ascribed to the longer exciton lifetime and fast electron transfer from nanoclusters to cocatalyst.Moreover,the issue of instability during reaction could be significantly inhibited by anchoring Zn2+onto the surface of nanoclusters,which gives the average efficacy of hydrogen evolution at 0.61±0.07 mL·h^(-1)·mgcatalyst^(-1),i.e.,27.3±2.9 mmol·h^(-1)·g_(catalyst)^(-1)(420 nm)with maintained 95.2%of original activity over 12 h illumination.
基金the National Natural Science Foundation of China(NSFC)(No.21773162)the Applied Basic Research Programs of Science and Technology Department of Sichuan Province(No.2020YJ0326)+1 种基金the State Key Laboratory of Supramolecular Structures and Materials of Jilin University(SKLSSM 202035)M.Z.is grateful to Sichuan University Postdoctoral Research Fund(No.2019SCU12073)and the Fundamental Research Funds for the Central Universities.
文摘Precursor compounds(PCs)link quantum dots(QDs)and magic-sized clusters(MSCs),which is pivotal in the conversion between QDs and MSCs.Here,for the first time,we report the transformation,synthesis,and composition of a type of ZnSe PCs.ZnSe PCs can be directly transformed to two different MSCs with the assistance of octylamine and acetic acid at room temperature.The two types of MSCs exhibit sharp absorption peaks at 299 and 328 nm which are denoted as MSC-299 and MSC-328.In the preparation of ZnSe PCs,diphenylphosphine(DPP)as an additive plays a key role which not only inhibits the thermal decomposition of Zn precursor,but also acts as a reducing agent to reduce the by-products produced in the reaction.The composition was explored by X-ray photoelectron spectroscopy,energy dispersive spectrometer,matrix-assisted laser desorption/ionization time-of-flight mass spectra with ZnSe PC powder appeared as white powder after purifying by toluene(Tol)and methanol(MeOH).The results indicate that the molar ratio of Zn/Se is 2:1 with a molecular of〜3,350 Da.Therefore,we propose that the molecular formula of ZnSe PCs is Zn_(32)Se_(16).In addition,at the molecular level,the covalent bond of Zn-Se is formed in ZnSe PCs.This study offers a deeper understanding of the transformation from PCs to MSCs and for the first time proposes the composition of PCs.Meanwhile,this research provides us with a new understanding of the role of DPP in the synthesis of colloidal semiconductor nanoparticles.
基金the National Key Research and Development Program of China(No.2024YFA1210001)the National Natural Science Foundation of China(No.22275126)+1 种基金the Natural Science Foundation of Sichuan Province(No.2023NSFSC0634)the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.sklssm 202522).
文摘Cadmium selenide(CdSe)is a model system that has been widely used to study the synthesis of semiconductor magic-size clusters(MSCs)and quantum dots(QDs),together with their formation pathways,optical properties,and quantum confinement effects.Here,we show the occurrence of MSC-330,MSC-360,MSC-390,and MSC-415 from a prenucleation-stage sample of CdSe in dispersion at temperatures much lower than the sample preparation temperature.The number represents the lowest energy peak in nanometers of optical absorption.We develop a model based on prenucleation clusters(PNCs)to explain and rationalize our experimental data,and propose that the MSCs are a group of isomers emerging from their corresponding precursor compounds(PCs).The PNC-MSC-415 isomerization is driven thermodynamically,with the loss in∆H∆Senthalpy(<0)and entropy(<0).With that,we introduce a PNC-based approach to control the MSC development in dispersion,and provide compelling evidence for the existence of the PNC and of two categories of MSCs displaying either absorption singlets or doublets.
基金the National Key Research and Development Program of China(No.2024YFA1210001)the National Natural Science Foundation of China(No.22275126)+1 种基金the Natural Science Foundation of Sichuan Province(No.2023NSFSC0634)the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.SKLSSM 202522).
文摘Isosbestic behavior has been traditionally deemed as a spectroscopic indicator of a chemical reaction,in which a reactant transforms directly to a product without intermediates.Room-temperature transformations of colloidal semiconductor magic-size clusters(MSCs)from MSC-a to MSC-b display interrupted spectral shifts in optical absorption with or without isosbestic behavior.We demonstrate that a multicomponent model explains consistently the pathway.The model invokes precursor compounds(PCs)of MSCs as intermediates,with three key steps from MSC-a to PC-a(step 1),to PC-b(step 2),and to MSC-b(step 3).Monomer substitution assists step 2(PC-a to PC-b).Based on the experimental result and theoretical study,we conclude that when step 1 or 2 or 3 is rate-determining,isosbestic behavior can be ideally perfect or distorted or absent,respectively.Our study provides a deeper understanding of isosbestic behavior and of MSC transformations that are assisted by PC intermediates and monomer substitution.
基金the National Key Research and Development Program of China(No.2024YFA1210001)the National Natural Science Foundation of China(No.22275126)the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.SKLSSM 202522).
文摘Little is known about the room-temperature formation of colloidal semiconductor magic-size clusters(MSCs)of II-VI ternary CdE1E2 from ZnE1E2.Here,we report the first synthesis of CdTeSe MSCs from ZnTeSe MSC-340(displaying a sharp optical absorption peaking at 340 nm)at room temperature.When ZnTeSe MSC-340 and Cd(OAc)2/OLA(made from cadmium acetate and oleylamine)were mixed,the former disappeared,while CdTeSe MSC-422 and/or MSC-399 developed.Based on our experimental data,we propose that the conversion proceeds via the interaction of Cd(OAc)2/OLA and the precursor compound of ZnTeSe MSC-340,PC-340.As such,ZnTeSe MSC-340 first isomerized to PC-340;via cation exchange PC-340 transformed to CdTeSe PCs.In turn,the resultant CdTeSe PC isomerized to CdTeSe MSCs,the process of which was rate-determining.Furthermore,we show that the transformation between CdTeSe MSC-422 and MSC-399 was reversible,providing strong evidence that they are a pair of isomers.Our study introduces a room-temperature avenue towards Cd-based MSCs from Zn-based ones,which follows anionic framework conservation and anionic number conservation.
基金the National Natural Science Foundation of China(NSFC)(No.22275126)the Natural Science Foundation of Sichuan Province(No.2023NSFSC0634)+3 种基金the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.SKLSSM 2024036)gratitude for NSFC(No.32000934)and the Natural Science Foundation of Sichuan Province(No.24NSFSC6433)for NSFC(No.22305162)the discussion on experimental data.For TEM,we thank College of Chemistry of Sichuan University(Dr.Feng Yang).
文摘Little is known about the synthesis of colloidal ternary semiconductor magic-size clusters(MSCs)and quantum dots(QDs)in an aqueous environment.We report here the first synthesis of aqueous-phase CdSeS MSC-380(displaying sharp optical absorption peaking at~380 nm)at room temperature and QDs at elevated temperatures.The reaction contains CdCl2·2.5H_(2)O,3-mercaptopropionic acid(MPA,HS-(CH_(2))2-COOH),selenourea(SeU,NH_(2)-C(Se)-NH_(2)),and thioacetamide(TAA,CH3-C(S)-NH_(2)).Prior to the nucleation and growth(N/G)of QDs,there are clusters formed at 25℃.The prenucleation-stage clusters are the precursor compound of CdSeS MSC-380(PC-380).The PC is relatively transparent in optical absorption;in the presence of a primary amine butylamine(BTA,CH3-(CH_(2))3-NH_(2)),the PC transforms to absorbing CdSeS MSC-380.At 80℃,the PC decreases and the N/G of CdSeS QDs appears.The present study paves the way to the aqueous-phase synthesis of ternary CdSeS MSCs and QDs,providing an in-depth understanding of the cluster formation in the prenucleation stage of CdSeS QDs.
基金the National Natural Science Foundation of China(No.22275126)the Natural Science Foundation of Sichuan Province(No.2023NSFSC0634)+1 种基金the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.SKLSSM 2023031)the National Natural Science Foundation of China(No.22305162).
文摘The formation pathway of colloidal semiconductor ZnSe magic-size clusters(MSCs)in a reaction that display an optical absorption doublet remains poorly understood.The reaction of Zn(OAc)_(2)/OLA(made from zinc acetate and oleylamine)and tri-noctylphosphine selenide(SeTOP)in OLA in the presence of diphenylphosphine(HPPh_(2))is studied,in which dMSC-345 displays a doublet peaking at 328/345 nm.We suggest that the development is from the clusters that form in the initial prenucleation stage of the reaction.The clusters are the precursor compound(PC-299)of MSC-299(displaying an absorption singlet peaking at 299 nm).PC-299 transforms to PC-345 at a later stage.The presence of alcohol(such as methanol or ethylene glycol)promotes another pathway,which is the PC-299 to PC-320 transformation.PC-320 transforms to dMSC-320(with a doublet at 305/320 nm),followed by dMSC-345 via PC-345.The present study provides additional evidence that clusters(PC-299)form and transform(such as to dMSC-345 via PC-345)in the prenucleation stage of ZnSe quantum dots(QDs).
基金K.Y.thanks the National Natural Science Foundation of China(No.21773162)the Fundamental Research Funds for the Central Universities,the Applied Basic Research Programs of Science and Technology Department of Sichuan Province(No.2020YJ0326)+5 种基金the State Key Laboratory of Polymer Materials Engineering of Sichuan University(No.sklpme2020-2-09)the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.SKLSSM 2021030)the National Major Scientific and Technological Special Project for“Significant New Drugs Development”(No.2019ZX09201005-005-002)M.Z.is grateful to the National Natural Science Foundation of China(No.22002099)China Postdoctoral Science Foundation(No.2020T130441)Sichuan University postdoctoral interdisciplinary Innovation Fund,and the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.SKLSSM 2021032).
文摘The formation pathway of aqueous-phase colloidal semiconductor magic-size clusters(MSCs)remains unrevealed.In the present work,we demonstrate,for the first time,a precursor compound(PC)-enabled formation pathway of aqueous-phase CdSe MSCs exhibiting a sharp absorption peaking at about 420 nm(MSC-420).The CdSe MSC-420 is synthesized with CdCl2 and selenourea as the respective Cd and Se sources,and with 3-mercaptopropionic acid or L-cysteine as a ligand.Absorption featureless CdSe PCs form first in the aqueous reaction batches,which transform to MSC-420 in the presence of primary amines.The coordination between primary amine and Cd^(2+)on PCs may be responsible to the PC-to-MSC transformation.Upon increasing the reactant concentrations or decreasing the CdCl_(2)-ligand feed molar ratios,the Cd precursor self-assembles into large aggregates,which may encapsulate the resulting CdSe PCs and inhibit their transformation to MSC-420.The present study sheds essential light on the syntheses and formation mechanisms of nanocrystals.
基金the National Natural Science Foundation of China(Nos.21773162 and 21573155)the Fundamental Research Funds for the Central Universities (No.SCU2015A002)+1 种基金the State Key Laboratory of Polymer Materials Engineering of Sichuan University (No.sklpme2018-2-08)the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University for SKLSSM 201830.H.F.and W.H.thank the National Major Scientific and Technological Special Project for "Significant New Drugs Development”(Nos.2018ZX09201009-005-004 and 2018ZX09201009-005-001).We thank Sichuan Univ of Analytical & Testing Center.We are in debt to Du Shanling Wang (Analytical & Testing Center,Sichuan University) for TEM.
文摘We report,for the first time,the synthesis of CdS magic-size clusters (MSCs) which exhibit a single sharp absorption peaking at ~ 361 nm,along with sharp band edge photoemission at ~ 377 nm and broad trap emission peaking at ~ 490 nm.These MSCs are produced in a singleensemble form without the contamination of conventional quantum dots (QDs) and/or other-bandgap clusters.They are denoted as MSC-361.We present the details of several controlled syntheses done in oleylamine (OLA),using C,d(NO3)2 or C,d(OAc)2 as a C,d source and thioacetamide (TAA) or elementary sulfur (S) as a S source.A high synthetic reproducibility of the reaction of Cd(NO3)2 and TAA to single-ensemble MSC-361 is achieved,the product of which is not contaminated by other bandgap clusters and/or QDs.In some cases,the reaction product exhibits an additional absorption peak at ~ 322 nm.We demonstrate that the two peaks,at 361 and 322 nm,do not evolve synchronously.Therefore,the 322 nm peak is not a higher order electronic transition of MSC-361,but due to the presence of another ensemble,namely MSC-322.The present study suggests that there is an outstanding need for the development of a physical model to narrow the knowledge gap regarding the electronic structure in these colloidal semiconductor CdS MSCs.
基金K.Y.thanks the National Natural Science Foundation of China(NSFC,No.21773162)the Fundamental Research Funds for the Central Universities,the Applied Basic Research Programs of Science and Technology Department of Sichuan Province(No,2020YJ0326)+3 种基金the State Key Laboratory of Polymer Materials Engineering of Sichuan University respectively for No.sklpme2020-2-09,and the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University for No.SKLSSM 2021030M.Z.is grateful to National Natural Science Foundation of China((NSFC,No.22002099)China Postdoctoral Science Foundation(No.2020T130441)Sichuan University postdoctoral interdisciplinary Innovation Fund and the Open Project of Key State Laboratory for Supramolecular Structures and Materials of Jilin University(No.SKLSSM 2021032)C.R.L.is grateful to the COVID-19 Science and Technology Emergency Project of Sichuan Province of China(No.2021YFS0408).
文摘Little is known about how to precisely promote the selective production of either colloidal semiconductor metal chalcogenide(ME),magic-size clusters(MSCs),or quantum dots(QDs).Recently,a two-pathway model has been proposed to comprehend their evolution;here,we reveal for the first time that the size of precursors plays a decisive role in the selected evolution pathway of MSCs and QDs.With the reaction of cadmium myristate(Cd(MA)2)and tri-n-octylphosphine selenide(SeTOP)in 1-octadecene(ODE)as a model system,the size of Cd precursors was manipulated by the steric hindrance of carboxylic acid(RCOOH)additive.Without RCOOH,the reaction produced both CdSe MSCs and QDs(from 100 to 240℃).With RCOOH,the reaction produced MSCs or QDs when R was small(such as CH3−)or large(such as C6H5−),respectively.According to the twopathway model,the selective evolution is attributed to the promotion and suppression of the self-assembly of Cd and Se precursors,respectively.We propose that the addition of carboxylic acid may occur ligand exchange with Cd(MA)2,causing the different sizes of Cd precursor.The results suggest that the size of Cd precursors regulates the self-assemble behavior of the precursors,which dictates the directed evolution of either MSCs or QDs.The present findings bring insights into the two-pathway model,as the size of M and E precursors determine the evolution pathways of MSCs or QDs,the understanding of which is of great fundamental significance toward mechanism-enabled design and predictive synthesis of functional nanomaterials.
基金supported by the National Natural Science Foundation of China(No.22171132)the Innovation Fund from Nanjing University(No.020514913419)the Program for Innovative Talents and Entrepreneurs in Jiangsu(Nos.020513006012 and 020513006014).
文摘Achieving nanoconfinement-controlled synthesis of nanoplatelets(NPLs)via solution process under ambient condition remains a challenge.In this work,we developed a general ligand-induced strategy to synthesize colloidal stable all-inorganic semiconductor NPLs with controllable lateral dimensions.By introducing certain metal salts(cations:Zn^(2+)and In^(3+),anions:NO_(3)^(−),BF_(4)^(−),or triflate OTf−),wurtzite-structured(WZ-)CdS,CdSe,CdTe,and alloy Cd1−xZnxSe NPLs were directly synthesized in solution through the controlled diffusion of magic-size clusters(MSCs)at room temperature.Mechanism studies revealed that destabilization of MSCs and nanoconfined growth in templates facilitated the formation of NPLs.The present study not only provides a new synthetic route for the preparation of NPLs but also helps to provide insight into their probable formation mechanism and presents an important advance toward the rational design of functional nanomaterials.
基金financial support from the Chinese Academy of Sciences (YSBR-007)the National Natural Science Foundation of China (22173098,21975253)+1 种基金the Fundamental Research Funds for the Central Universities (20720220009)the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘Both semiconductor nanocrystals and organic molecules are important photofunctional materials for an array of applications.It is interesting to examine the intermediate regime between these two families,which can be interpreted as the strong-confinement limit of the nanocrystals or alternatively as the large-size limit of molecules.Here,we choose Cd_(3)P_(2) magic-size clusters(MSCs)as a unique platform and apply time-resolved spectroscopy to investigate their spectral and dynamic properties.We find that these small clusters display molecular-like vibronic progression on their absorption and emission spectra and a large Stokes shift,which leads to well-separated transient absorption bleach and stimulated emission signals distinct from typical nanocrystals.On the other hand,such small size MSCs can still accommodate biexciton states,and the strongly enhanced Coulombic interactions lead to very fast dephasing of the biexciton resonance as well as rapid biexciton Auger annihilation(1.5 ps).Further,temperature-dependent measurements provide evidence for the transformation of band-edge excitons to localized excitons,with the localization likely driven by the softened lattice in these small-size clusters.These collective results demonstrate that strongly-confined nanoclusters indeed bridge the gap between nanocrystals and molecules,and can be a unique library to search for exotic excited state properties.
基金support from the Deutsche Forschungsgemeinschaft(DFG)under contract BA 1422/22-1support of the Research Center Program of Institute for Basic Science(IBS-R006-D1)in Republic of Korea.
文摘Magic-sized(CdSe)_(13) clusters(MSCs)represent a material class at the boundary between molecules and quantum dots that exhibit a pronounced and well separated excitonic fine structure.The characteristic photoluminescence is composed of exciton bandgap emission and a spectrally broad mid-gap emission related to surface defects.Here,we report on a thermally activated energy transfer from fine-structure split exciton states to surface states by using temperature dependent photoluminescence excitation spectroscopy.We demonstrate that the broad mid-gap emission can be suppressed by a targeted Mn-doping of the MSC leading to the characteristic orange luminescence of the^(4)T_(1)→^(6)A_(1)Mn^(2+)transition.The energy transfer to the Mn^(2+)states is found to be significantly different than the transfer to the surface defect states,as the activation of the dopant emission requires a spin-conserving charge carrier transfer that only dark excitons can provide.
