We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots), by combining Qdot absorbance spectra with detailed elemental analysis suspensions. At high energies, molar extinction coefficient epsilon increases volume d(3) and agrees theoretical calculations using Maxwell-Garnett effective medium theory bulk values for dielectric function. This demonstrates that confinement has no influence on in this spectral range, it provides an...

Inductively coupled plasma mass spectrometry (ICP-MS) was combined with UV–vis−NIR spectrophotometry and transmission electron microscopy to determine the nanocrystal composition molar extinction coefficient ϵ of colloidal PbSe quantum dot (Q-PbSe) suspensions. The ICP-MS results show a nonstoichiometric Pb/Se ratio, systematic excess lead for all samples studied. observed ratio is consistent faceted spherical Q-PbSe model, composed quasi stoichiometric core terminated by Pb surface shell....

PbS Qdots are synthesized using PbCl2 and elemental sulfur as precursors. The available size range is significantly expanded tri-n-octylphosphine (TOP), enabling the synthesis of monodisperse suspensions with a mean varying between 3 10 nm. ligand composition dynamics investigated nuclear magnetic resonance (NMR) spectroscopy. We show that passivated solely by highly dynamic OlAm ligands, even when TOP employed during synthesis. In this respect, compound strongly modifying Qdot synthesis,...

A binary ligand system composed of aliphatic carboxylic acids and primary amines various chain lengths is commonly employed in diverse synthesis methods for CsPbBr3 nanocrystals (NCs). In this work, we have carried out a systematic study examining how the concentration ligands (oleylamine oleic acid) resulting acidity (or basicity) affects hot-injection NCs. We devise general scheme cesium lead bromide NCs which allows control over size, size distribution, shape, phase (CsPbBr3 or Cs4PbBr6)...

Solution nuclear magnetic resonance spectroscopy (NMR) is used to identify and quantify the organic capping of colloidal PbSe nanocrystals (Q-PbSe). We find that consists primarily tightly bound oleic acid ligands. Only a minor part ligand shell (0-5% with respect number ligands) composed tri- n-octylphosphine. As result, tuning Q-PbSe size during synthesis achieved by varying concentration. By combining NMR results inductively coupled plasma mass spectrometry, complete structural model...

Sulfide-based luminescent materials have attracted a lot of attention for wide range photo-, cathodo- and electroluminescent applications. Upon doping with Ce3+ Eu2+, the luminescence can be varied over entire visible region by appropriately choosing composition sulfide host. Main application areas are flat panel displays based on thin film electroluminescence, field emission ZnS-based powder electroluminescence backlights. For these applications, special is given to BaAl2S4:Eu, ZnS:Mn...

The effect of short-chain alcohols and acetonitrile on the ligand shell composition photoluminescence quantum yield purified PbSe CdSe dots is analyzed by solution NMR spectroscopy. We find that induce release X-type carboxylate ligands with a concurrent reduction yield, while does not. interpret this difference in terms protic or aprotic character both nonsolvents, where only can provide protons needed to desorb ligands. similar differences between when used as nonsolvents during...

Current colloidal synthesis methods for CdSe nanoplatelets (NPLs) routinely yield samples that emit, in discrete steps, from 460 to 550 nm. A significant challenge lies with obtaining thicker NPLs, further widen the emission range. This is at present typically achieved via atomic layer deposition onto cores, or by synthesizing NPL core/shell structures. Here, we demonstrate a novel reaction scheme, where start 4.5 monolayer (ML) NPLs and increase thickness two-step switches 2D 3D growth. The...

Recently, solution NMR-based approaches have been developed that represent useful new tools for the in situ characterization of capping ligand colloidal nanocrystal dispersions. So far, this development has focused mainly on tightly bound ligands (no exchange) or slow exchange with surface. In such systems, can be identified and its amount interaction quantified via 1D 1H NMR, 1H−13C HSQC, DOSY spectra. Here, we explore case where are fast Using dodecylamine-stabilized CdTe (Q-CdTe|DDA)...

Although wurtzite cadmium selenide quantum dots (wz-CdSe QDs) are one of the best explored colloidal nanomaterials, no detailed investigation optical properties zincblende (zb-CdSe has been performed until now. Typically, it is assumed that this material shows same behavior as modification. To investigate this, we present a study on zb-CdSe QDs, yielding electronic band gap to size relation (sizing curve), extinction coefficient at short wavelengths, and oscillator strength transition....

We present an approach for the synthesis of ternary copper indium sulfide (CIS) and quaternary zinc (CIZS) nanocrystals (NCs) by means partial cation exchange with In3+ Zn2+. The consists a sequential three-step synthesis: first, binary Cu2S NCs were synthesized, followed homogeneous incorporation in situ cation-exchange reaction, leading to CIS NCs. In last step, second was performed where Zn2+ partially replaced Cu+ cations at surface, creating ZnS-rich shell preservation size shape. By...

We review the recent progress in quantitative understanding of light absorption by colloidal semiconductor quantum dots within framework Maxwell-Garnett (MG) effective medium theory. The fundamental quantities used to describe dispersed absorbers—intrinsic coefficient, molar coefficient and cross section—are introduced it is shown that MG model reduces a local field correction case strongly diluted dispersions. correspondence between experimental results this so-called approximation first...

We measured the intrinsic ground-state exciton dephasing and population dynamics in colloidal quasi-two-dimensional (2D) CdSe nanoplatelets at low temperature (5--50 K) using transient resonant four-wave mixing heterodyne detection. Our results indicate that below 20 K is lifetime limited, with being as fast 1 ps. This consistent an given by a radiative decay due to large in-plane coherence area of center-of-mass motion these quasi-2D systems compared spherical nanocrystals. The rate such 2D...

Colloidal semiconductor quantum structures allow controlling the strong confinement of charge carriers through material composition and geometry. Besides being a unique platform to study fundamental effects, these materials attracted considerable interest due their potential in opto-electronic communication applications. Heteronanostructures like CdSe/CdS offer new prospects tailor optical properties as they take advantage small conduction band offset allowing tunability electron...

In this work, we demonstrate the successful application of two-dimensional (2D) materials, i.e., graphene and functionalized MoS2, in perovskite solar cells (PSCs) by interface engineering standard mesoscopic n–i–p structure. The use 2D materials has dual role to improve both stability overall power conversion efficiency (PCE) PSCs compared devices. is successfully extended large-area modules (PSMs), achieving PCEs 13.4% 15.3% on active areas 108 cm2 82 cm2, respectively. This performance...

We present the synthesis of novel disk-shaped hexagonal Cu2Te nanocrystals with a well-defined stoichiometric composition and tunable diameter thickness. Subsequent cation exchange Cu to Cd at high temperature (180 °C) results in highly fluorescent CdTe nanocrystals, less than 1 mol % residual remaining lattice. The procedure preserves overall disk shape, but is accompanied by substantial reconstruction anion sublattice, resulting reorientation c-axis from surface normal into plane...

We report a comprehensive study on the two-photon absorption cross sections of colloidal CdSe nanoplatelets, -rods, and -dots different sizes by means z-scan excitation spectroscopy. Platelets combine large particle volumes with ultra strong confinement. In contrast to weakly confined nanocrystals, TPA nanoplatelets scale superlinearly volume (V(∼2)) show ten times more efficient than nanorods or dots. This unexpectedly shape dependence goes well beyond effect local fields. The larger...

Ligand exchange is a much-used method to increase the conductivity of colloidal quantum-dot films by replacing long insulating ligands on surfaces with shorter ones. Here we show that while some indeed replace original ones as expected, others may be used controllably remove native and induce epitaxial necking specific crystal facets. In particular, demonstrate amines strip lead oleate from (100) PbSe quantum dots. This leads QDs results in cubic superlattices epitaxially connected QDs. The...

The lateral dimensions of CdSe nanoplatelets have a strong and unique influence on their opto-electronic properties, with sizes that can be tuned from the weak to exciton confinement regime. There are state-of-the-art reports several nanoplatelet syntheses; however, at present only thickness is well-controlled. We demonstrate here we achieve control over aspect ratio overall nanoplate area by carefully adjusting reagents induce in-plane growth. A variation fraction hydrated Cd(OAc)2 in...

In the past few years, several protocols have been reported on synthesis of CdSe nanoplatelets with narrow photoluminescence (PL) spectrum, high PL quantum efficiency, and short exciton lifetime. The corresponding core/shell are however still mostly based CdSe/CdS, which possess an extended lifetime a strong red shift band-edge absorption emission, in accordance quasi-type-II band alignment. Here we report robust procedure to grow ZnS shell around at moderate temperatures 100–150 °C, improve...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSolution-Processed Hybrid Graphene Flake/2H-MoS2 Quantum Dot Heterostructures for Efficient Electrochemical Hydrogen EvolutionLeyla Najafi†¶‡, Sebastiano Bellani†‡, Beatriz Martín-García†§, Reinier Oropesa-Nuñez†, Antonio Esau Del Rio Castillo†, Mirko Prato⊥, Iwan Moreels†§, and Francesco Bonaccorso*†View Author Information† Labs, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy§ Nanochemistry Department, Italy⊥ Materials...

We report on the synthesis of silver (Ag)-doped CdSe nanoplatelets (NPLs) via postsynthesis cation exchange, using acetate as Ag precursor. High-resolution transmission electron microscopy and X-ray diffraction confirmed that NPLs maintain their morphology crystal structure after doping when executing exchange under reduced temperature in an ice bath. Spectroelectrochemistry transient absorption spectroscopy revealed Ag+ acts acceptor dopant. results emission is tunable from 609 to 880 nm,...

Abstract The technological challenge imposed by the time resolution essential to achieve real-time molecular imaging calls for a new generation of ultrafast detectors. In this contribution, we demonstrate that CdSe-based semiconductor nanoplatelets can be combined with standard scintillator technology 80 ps coincidence on hybrid functional pixel. This result contrasts fact overall detector light output is considerably affected loss index-light-guiding. Here, exploit principle 511 keV energy...