Interplay between Perovskite Magic-Sized Clusters and Amino Lead Halide Molecular Clusters

Recent progress has been made on the synthesis and characterization of metal halide perovskite magic-sized clusters (PMSCs) with ABX3 composition (A=CH3NH3+ or Cs+, B=Pb2+, and X=Cl−, Br-, or I-). However, their mechanism of growth and structure is still not well understood. In our effort to understand their structure and growth, we discovered that a new species can be formed without the CH3NH3+ component, which we name as molecular clusters (MCs). Specifically, CH3NH3PbBr3 PMSCs, with a characteristic absorption peak at 424 nm, are synthesized using PbBr2 and CH3NH3Br as precursors and butylamine (BTYA) and valeric acid (VA) as ligands, while MCs, with an absorption peak at 402 nm, are synthesized using solely PbBr2 and BTYA, without CH3NH3Br. Interestingly, PMSCs are converted spontaneously overtime into MCs. An isosbestic point in their electronic absorption spectra indicates a direct interplay between the PMSCs and MCs. Therefore, we suggest that the MCs are precursors to the PMSCs. From spectroscopic and extended X-ray absorption fine structure (EXAFS) results, we propose some tentative structural models for the MCs. The discovery of the MCs is critical to understanding the growth of PMSCs as well as larger perovskite quantum dots (PQDs) or nanocrystals (PNCs).

Download Full-text

Synthesis and Characterization of Trivalent Cerium Complexes of p-tert-Butylcalix[4,6,8]Arenes: Effect of Organic Solvents

Journal of Chemistry ◽

10.1155/2013/494392 ◽

2013 ◽

Vol 2013 ◽

pp. 1-9 ◽

Cited By ~ 3

Author(s):

Md. Hasan Zahir

Keyword(s):

Organic Solvents ◽

Electronic Absorption ◽

Electronic Absorption Spectra ◽

H Nmr ◽

Protic Solvents ◽

Elemental Analyses ◽

Ft Ir ◽

X Ray Absorption ◽

Molar Extinction Coefficients

Reaction of Ce3+with p-tert-butylcalix[n]arene (n=4,6,8) yields purple crystalline complexes structurally as [Ce(p-tert-butylcalix[4]arene-3H)2(NO3)(DMF)x](2 −x)DMF (1), [Ce(p-tert-butylcalix[6]arene-4H)2(NO3)(DMF)x](3 −x)DMF (2), and [Ce(p-tert-butylcalix[8]arene-7H)2(NO3)(DMF)6] (3), whereDMF=N,N-dimethylformamide. The properties and coordination characteristics of the three calixarene complexes were determined by elemental analyses, electronic absorption, X-ray absorption spectroscopy (EXAFS), TG-DTA, FT-IR, SEM, and1H-NMR spectroscopy. The effect of various organic solvents on complexes1,2, and3has been discussed based on results from electronic absorption spectra. The polar protic solvents showed the most significant molar extinction coefficients in comparison with those of nonpolar and polar aprotic solvents. The Ce3+ions in the complexes are proved to combine with the ligand phenolic groups, oxygen atoms of DMF molecules, and/or OH−ions.

Download Full-text

Exploring the physics of cesium lead halide perovskites quantum dots via Bayesian inference of the photoluminescence spectra in automated experiment

Nanophotonics ◽

10.1515/nanoph-2020-0662 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Amanda Heimbrook ◽

Kate Higgins ◽

Sergei V. Kalinin ◽

Mahshid Ahmadi

Keyword(s):

Quantum Dots ◽

Bayesian Inference ◽

Metal Halide ◽

Automated Synthesis ◽

Metal Halide Perovskite ◽

Perovskite Quantum Dots ◽

Halide Perovskite ◽

Bayesian Inference Framework ◽

Automated Platform ◽

Lead Halide

Abstract The unique optoelectronic properties of metal halide perovskite quantum dots (QDs) make them promising candidates for applications in light-emitting diodes (LEDs), scintillators, and other photonic devices. The automated micropipetting synthesis platform equipped with an optical reader enables the opportunity for high throughput synthesis and photoluminescent (PL) characterization of metal halide perovskite QDs for the first time. Here, we explore the compositional dependence of the PL behavior and stability of the combinatorial library of cesium lead halide (CsPbX3) perovskites QDs via the automated platform. To study the stability of synthesized QDs in the binary and ternary configurations, we study the time-dependent PL properties using previously developed machine learning analysis. To systematically explore the PL behavior in the ternary CsPbX3 QDs system, we introduce the Bayesian inference framework that allows the probabilistic fit of multiple models to the PL data and establishes both optimal model and model parameter robustly. Furthermore, these behaviors can be used as a control parameter for the navigation of the multidimensional compositional spaces in automated synthesis. This analysis shows the nonuniformity of the PL peak behavior in the ternary CsPbX3 QDs system. Further, the analysis confirms narrow size distribution and good quality of CsPbBr3 QDs alloyed with low concentrations of iodide and chloride. We note that Bayesian Inference fit parameters can be further used as a control signal for navigation of the chemical spaces in automated synthesis.

Download Full-text

The Effect of KOH Activation in Synthesis and Characterization of Zeolitic Imidazolate Frameworks-8 (ZIF-8) Templated Mesoporous Carbon

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1123.78 ◽

2015 ◽

Vol 1123 ◽

pp. 78-83

Author(s):

Miratul Alifah ◽

Vika Ayu Devianti ◽

Amirul Mukminin ◽

Yulia Rachmawati ◽

Muhammad Ainul Fahmi ◽

...

Keyword(s):

Zinc Nitrate ◽

Absorption Peak ◽

Synthesis Process ◽

Koh Activation ◽

Nitrate Hexahydrate ◽

Zeolitic Imidazolate Frameworks ◽

Xrd Pattern ◽

Carbon Particles ◽

Characteristic Absorption Peak

ZIF - 8 material has been successfully synthesized through a reaction between zinc nitrate hexahydrate with 2 - metilimidazol in the dimethylformamide solvent in solvotermal condition. Synthesis process is carried out at 120oC for 24 hours . The results show that the characterization by XRD diffractogram synthesized ZIF - 8 has a characteristic peak at 2θ = 7.4o; 12.7o; 16.5oand 18.0ocorresponding to the characteristic peaks of ZIF - 8 standard . The results of ZIF - 8 templated carbon show the XRD pattern of amorphous carbon material, while the carbon activated KOH show peak K2CO3at 2θ = 31.6o. FTIR spectra of synthesized ZIF - 8 has a absorption peak at 420; 760 ; 990 ; 1147 and 1585 cm-1which is the characteristic absorption peak of ZIF-8 solids. Then ZIF - 8 characteristic peaks disappear after activated with KOH. Morphology of the ZIF-8 has plumage regular rectangular in shape , and morphology of the resulting carbon particles are also the same rectangular shape with ZIF-8 template.

Download Full-text

All-inorganic lead-free metal halide perovskite quantum dots: progress and prospects

Chemical Communications ◽

10.1039/d1cc01783g ◽

2021 ◽

Author(s):

Yuanqian Tang ◽

Songzhi Tang ◽

Ming Luo ◽

Yanmei Guo ◽

Yingping Zheng ◽

...

Keyword(s):

Quantum Dots ◽

Quantum Confinement ◽

Quantum Confinement Effect ◽

Optical Gain ◽

Lead Free ◽

Metal Halide Perovskite ◽

Perovskite Quantum Dots ◽

Halide Perovskite ◽

Free Metal ◽

Lead Halide

Lead halide perovskite quantum dots have drawn worldwide attention due to their quantum confinement effect and excellent optical gain properties. It is worth noting that due to the toxicity of...

Download Full-text

EXELFS Studies of Carbon Fibers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133953 ◽

1990 ◽

Vol 48 (2) ◽

pp. 72-73

Author(s):

V. Serin ◽

K. Hssein ◽

G. Zanchi ◽

J. Sévely

Keyword(s):

Carbon Fibers ◽

Energy Analysis ◽

Electron Excitation ◽

Complex Structures ◽

High Modulus ◽

Promising Technique ◽

X Ray ◽

Fine Structures ◽

X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

Download Full-text

Synthesis and Characterization of Nanocrystalline ZnO Powders by a Direct Thermal Decomposition Route Using Zinc Nitrate Hexahydrate

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.770.68 ◽

2013 ◽

Vol 770 ◽

pp. 68-71 ◽

Cited By ~ 1

Author(s):

Supphadate Sujinnapram ◽

Uraiphorn Termsuk ◽

Atcharawan Charoentam ◽

Sutthipoj Sutthana

Keyword(s):

Thermal Decomposition ◽

Crystallization Temperature ◽

Zinc Nitrate ◽

Zinc Nitrate Hexahydrate ◽

Absorption Peak ◽

Synthesis And Characterization ◽

Nitrate Hexahydrate ◽

Different Temperatures ◽

Zno Powders

The nanocrystalline ZnO powders were synthesized by a direct thermal decomposition using zinc nitrate hexahydrate as starting materials. The precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at 325 oC. The precursors were calcined at different temperatures of 400, 500, and 600°C for 4 h. The structure of the prepared samples was studied by XRD, confirming the formation of wurtzite structure. The synthesized powders exhibited the UV absorption below 400 nm (3.10 eV) with a well defined absorption peak at around 285 nm (4.35 eV). The estimated direct bandgaps were obtained to be 3.19, 3.16, and 3.14 eV for the ZnO samples thermally decomposed at 400, 500, and 600°C, respectively.

Download Full-text

Database of ab initio L-edge X-ray absorption near edge structure

Scientific Data ◽

10.1038/s41597-021-00936-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Yiming Chen ◽

Chi Chen ◽

Chen Zheng ◽

Shyam Dwaraknath ◽

Matthew K. Horton ◽

...

Keyword(s):

High Throughput ◽

Scattering Theory ◽

Research Community ◽

Metal Compounds ◽

Edge Structure ◽

X Ray ◽

Initial Release ◽

Computational Workflow ◽

X Ray Absorption

AbstractThe L-edge X-ray Absorption Near Edge Structure (XANES) is widely used in the characterization of transition metal compounds. Here, we report the development of a database of computed L-edge XANES using the multiple scattering theory-based FEFF9 code. The initial release of the database contains more than 140,000 L-edge spectra for more than 22,000 structures generated using a high-throughput computational workflow. The data is disseminated through the Materials Project and addresses a critical need for L-edge XANES spectra among the research community.

Download Full-text

Burstein-Moss shift of lead halide perovskite quantum dots induced by electron injection from graphene oxide

Applied Surface Science ◽

10.1016/j.apsusc.2021.149003 ◽

2021 ◽

Vol 545 ◽

pp. 149003

Author(s):

Shengnan Ni ◽

Haijun Qin ◽

Jianfeng Wen ◽

Xinyu Li ◽

Ming Li ◽

...

Keyword(s):

Quantum Dots ◽

Graphene Oxide ◽

Electron Injection ◽

Perovskite Quantum Dots ◽

Halide Perovskite ◽

Lead Halide

Download Full-text

Heterogeneous Post-Passivation of Inorganic Cesium Lead Halide Perovskite Quantum Dots for Efficient Electroluminescent Devices

Journal of Materials Chemistry C ◽

10.1039/d0tc05856d ◽

2021 ◽

Author(s):

Xuefei Li ◽

Qingqing Yang ◽

Liuqing Yang ◽

Shumeng Wang ◽

Junqiao Ding ◽

...

Keyword(s):

Quantum Dots ◽

Electroluminescent Devices ◽

Perovskite Quantum Dots ◽

Halide Perovskite ◽

Lead Halide

A heterogeneous post-passivation has been demonstrated by using formamidiniu bromide (FABr) to compensate the surface bromo vacancy of inorganic cesium lead halide perovskite quantum dots (QDs). Benefitting from its limited...

Download Full-text