Search query: Ultra-large-scale syntheses of monodisperse nanocrystals

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abstract: The development of nanocrystals has been intensively pursued, not only for their fundamental scientific interest, but also for many technological applications1,2,3. The synthesis of monodisperse nanocrystals (size variation <5% is of key importance, because the properties of these nanocrystals depend strongly on their dimensions. For example, the colour sharpness of semiconductor nanocrystal based optical devices is strongly dependent on the uniformity of the nanocrystals3,4,5,6, and monodisperse magnetic nanocrystals are critical for the next generation multi terabit magnetic storage media7,8,9. For these monodisperse nanocrystals to be used, an economical mass production method needs to be developed. Unfortunately, however, in most syntheses reported so far, only sub gram quantities of monodisperse nanocrystals were produced. Uniform sized nanocrystals of CdSe (refs 10,11) and Au (refs 12,13) have been produced using colloidal chemical synthetic procedures. In addition, monodisperse magnetic nanocrystals such as Fe (refs 14,15) Co (refs 16 18) g Fe2O3 (refs 19,20) and Fe3O4 (refs 21,22) have been synthesized by using various synthetic methods23. Here, we report on the ultra large scale synthesis of monodisperse nanocrystals using inexpensive and non toxic metal salts as reactants. We were able to synthesize as much as 40 g of monodisperse nanocrystals in a single reaction, without a size sorting process. Moreover, the particle size could be controlled simply by varying the experimental conditions. The current synthetic procedure is very general and nanocrystals of many transition metal oxides were successfully synthesized using a very similar procedure.
author_names: Jongnam Park

Kwang Jun An

Yosun Hwang

Je-Guen Park

H J Noh

Jae-Young Kim

Jae-hoon Park

Nong-Moon Hwang

Taeghwan Hyeon
title: Ultra large scale syntheses of monodisperse nanocrystals
venue: Nature materials
year: 2004

abstract: A rational synthetic method is developed to produce monodisperse metal sulfide nanocrystals (NCs) in organic nonpolar solutions by using (NH(4)(2)S as a sulfide precursor. (NH(4)(2)S is stabilized in an organic primary amine solution and exhibits high reactivity toward metal complexes. This novel technique exhibits wide applicability for organic phase metal sulfide NC synthesis: a large variety of monodisperse NCs have been synthesized, including Cu(2)S, CdS, SnS, ZnS, MnS, Ag(2)S, and Bi(2)S(3) The stoichiometric reactions between (NH(4)(2)S and metal salts afford high conversion yields, and large scale production of monodisperse NCs (more than 30 g) can be synthesized in a single reaction. The high reactivity of (NH(4)(2)S enables low temperature <100 degC) syntheses, and the air stable materials (such as CdS NCs) can be produced in air. Moreover, this low temperature technique can be used to produce small size NCs which are difficult to be synthesized by the conventional high temperature methods, such as sub 5 nm Ag(2)S and Bi(2)S(3) quantum dots.
author_names: Haitao Zhang

Byung-Ryool Hyun

Frank W Wise

Richard D Robinson
title: A generic method for rational scalable synthesis of monodisperse metal sulfide nanocrystals.
venue: Nano letters
year: 2012

abstract: Magnetite (Fe3O4) nanocrystals (MNCs) are among the most studied magnetic nanomaterials, and many reports of solution phase synthesis of monodisperse MNCs have been published. However, lack of reproducibility of MNC synthesis is a persistent problem, and the keys to producing monodisperse MNCs remain elusive. Here, we define and explore synthesis parameters in this system thoroughly to reveal their effects on the product MNCs. We demonstrate the essential role of benzaldehyde and benzyl benzoate produced by oxidation of benzyl ether, the solvent typically used for MNC synthesis, in producing monodisperse MNCs. This insight allowed us to develop stable formulas for producing monodisperse MNCs and propose a model to rationalize MNC size and shape evolution. Solvent polarity controls the MNC size, while short ligands shift the morphology from octahedral to cubic. We demonstrate preparation of specific assemblies with these MNCs. This standardized and reproducible synthesis of MNCs of well controlled size, shape, and magnetic properties demonstrates a rational approach to stabilizing and expanding existing protocols for nanocrystal syntheses and may drive practical advances including enhanced MRI contrast, higher catalytic selectivity, and more accurate magnetic targeting.
author_names: Liang Qiao

Zheng Fu

Ji Li

John Ghosen

Ming Zeng

Jonathan F Stebbins

Paras N Prasad

Mark T Swihart
title: Standardizing Size and Shape Controlled Synthesis of Monodisperse Magnetite (Fe3O4) Nanocrystals by Identifying and Exploiting Effects of Organic Impurities.
venue: ACS nano
year: 2017

abstract: Abstract Single phase cubic BaLnF 5 (Ln La Lu, Y) nanocrystals are successfully synthesized via a common facile solvothermal route using oleic acid as surfactant. It is found that the smaller the Ln 3+ radius, the easier to precipitate the undesired BaLn 2 F 8 phase in the reaction system along with the formation of BaLnF 5 In this case, the appropriate reaction temperature is required to obtain single BaLnF 5 nanophase. Measurements on the up conversion emission behaviors of the Yb 3+ /Er 3+ (Tm 3+ BaLaF 5 and Yb 3+ /Er 3+ (Tm 3+ BaLuF 5 nanocrystals demonstrate that BaLnF 5 are desirable up conversion hosts. In addition, the Ce 3+ /Ln 3+ (Ln Tb, Eu, Dy, Sm) BaGdF 5 nanocrystals are found exhibiting multicolor down conversion emissions.
author_names: Lei Lei

Daqin Chen

Feng Huang

Yunlong Yu

Yuansheng Wang
title: Syntheses and optical properties of monodisperse BaLnF5 (Ln La Lu, Y) nanocrystals
year: 2012

abstract: Spinel ferrite nanocrystals (NCs) have shown great promise for a wide variety of electromagnetic and medical applications. In this work, the AC magnetic properties of nonstoichiometric manganese and cobalt ferrites (MxFe3 xO4, M Mn, Co) NCs are systematically studied as a function of composition. Samples of very similar average size and shape, but different Mn to Fe and Co to Fe ratios are prepared to study the effect of composition. Conventional syntheses are combined with a size selective precipitation method using oleic acid as an antisolvent yielding nearly monodisperse samples. DC and AC magnetic measurements shows that introducing Co to the ferrite crystal increases the blocking temperatures and magnetic anisotropies of the nanocrystals with corresponding shifts in AC magnetic susceptibilities, while manganese ferrites are relatively insensitive to the variation in compositions as size and shape dominate over crystal anisotropy. The systematic AC magnetic characterizations of superparamagnetic Mnx.
author_names: Dichen Li

Hongseok Yun

Benjamin T Diroll

Vicky V T Doan-Nguyen

James Makoto Kikkawa

Christopher B Murray
title: Synthesis and Size Selective Precipitation of Monodisperse Nonstoichiometric MxFe3 xO4 (M Mn, Co) Nanocrystals and Their DC and AC Magnetic Properties
year: 2016

abstract: Abstract Solution phase syntheses and size selective separation methods to prepare semiconductor and metal nanocrystals, tunable in size from ~1 to 20 nm and monodisperse to =5% are presented. Preparation of monodisperse samples enables systematic characterization of the structural, electronic, and optical properties of materials as they evolve from molecular to bulk in the nanometer size range. Sample uniformity makes it possible to manipulate nanocrystals into close packed, glassy, and ordered nanocrystal assemblies (superlattices, colloidal crystals, supercrystals) Rigorous structural characterization is critical to understanding the electronic and optical properties of both nanocrystals and their assemblies. At inter particle separations 5 100 A, dipole dipole interactions lead to energy transfer between neighboring nanocrystals, and electronic tunneling between proximal nanocrystals gives rise to dark and photoconductivity. At separations <5 A, exchange interactions cause otherwise insulating ass.
author_names: Christopher B Murray

Cherie R Kagan

Moungi G Bawendi
title: Synthesis and Characterization of Monodisperse Nanocrystals and Close Packed Nanocrystal Assemblies
year: 2000

abstract: The title nanocrystals are solvothermally synthesized from mixtures of Ln(NO3)3 (Ln: La Lu, Y) Ba(NO3)2, NH4F, NaOH, EtOH, oleic acid, and H2O (autoclave, 180 degC, 24 h)
author_names: Lei Lei

Daqin Chen

Feng Huang

Yunlong Yu
title: Syntheses and Optical Properties of Monodisperse BaLnF5 (Ln: La Lu, Y) Nanocrystals.
year: 2012

abstract: A novel facile approach, sol solvothermal process, is reported here for syntheses of nearly monodisperse inorganic nanocrystals (NCs) such as elementary metals, simple metal oxides, composite oxides, and selenides by using inexpensive metal salts and environmental friendly solvents as reactants without a further size selection treatment. The results revealed that mean diameter of the synthetic NCs measured by Dynamic Light Scattering (DLS) was consistent with the observed size by Field emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) images, demonstrating the agglomeration free feature of the nanosized crystals. Moreover, the particle size and morphology of the synthetic NCs could be effectively controlled under various appropriate sets of experimental conditions.
author_names: Sheng Yao

Xuchen Lu

Xiaohui Li

Tengjiao Ou
title: A facile approach for syntheses of nearly monodisperse nanocrystals: sol solvothermal process.
venue: Journal of nanoscience and nanotechnology
year: 2009

abstract: AbstractA facile strategy using cheap and readily available precursors has been successfully developed for the synthesis of rare earth doped hexagonal phase NaYF4 nanocrystals with uniform shape and small particle size as well as strong photoluminescence. Due to their optical properties and good biocompatibility, these multicolor nanocrystals were successfully used as a bio tag for cancer cell imaging. This novel synthetic method should also be capable of extension to the synthesis of other fluoride nanocrystals such as YF3 and LaF3.
author_names: Mingliang Deng

Yingxin Ma

Sheng Huang

Gaofei Hu

Leyu Wang
title: Monodisperse upconversion NaYF4 nanocrystals: Syntheses and bioapplications
year: 2011

abstract: Monodisperse PbS nanocrystals with controlled spherical, octahedral, and cubic shapes were synthesized via simple thermal decomposition of lead oleate complex precursors by simply changing the synthetic procedure and the Pb and S precursor concentrations. Spherical nanocrystals with mixed facets exposed and octahedral nanocrystals with {111} facets exposed were synthesized through a "hot injection" process. Cubic nanocrystals with {100} facets exposed were prepared via a "heating up" growth process. The three types of monodisperse PbS nanocrystals showed shape and facet dependent photoresponse behaviors. The thin film of cubic PbS nanocrystals with {100} facets exposed exhibited the largest current enhancement (91.3% after irradiation as compared with the other two shapes. Meanwhile, the results of density functional theory calculation confirmed that the photoexcited electrons can be driven in the {100} facets with mixed Pb/S atoms through s bonding consisting of the overlapping s(Pb 6s) p(S 3p) orbitals. This significantly shortens the carrier transfer distance and reduces the carrier recombination. The present facet engineering strategy can be extended to the other semiconducting nanocrystal syntheses and solar energy conversion applications.
author_names: Chenyang Zha

Cheng Ji

Junjie Zhang

Liming Shen

Xiaoyan Zhang

Shuai Dong

Ningzhong Bao
title: Facet engineering of monodisperse PbS nanocrystals with shape and facet dependent photoresponse activity
year: 2016