Colloidal CdTe Research Articles

Temperature-dependent photovoltaic characterization of a CdTe/CdSe nanocrystal’s solar cell

An all-inorganic thin film solar cell was fabricated with colloidal CdTe and CdSe nanocrystals. Its temperaturedependent photovoltaic characterization was measured, and an open circuit voltage decay technique was used to determine the electron lifetime. The photovoltaic parameters, such as the exact carrier lifetime, were remarkably different between under low-temperature region and under temperature above 267 K. It is suggested that the temperature-dependent carrier conductivity results from a thermally-activated hopping process and this nanocrystals device is a kind of donor-acceptor solar cell.

CdTe-CdSe nanocrystals capped with dimethylaminoethanethiol as ultrasensitive fluorescent probes for chromium(VI)

We report on the synthesis of water-soluble luminescent colloidal CdTe nanocrystals capped with various stabilizers (mercaptopropanol, thioglycolic acid, mercaptosuccinic acid, mercaptopropionic acid, L-cysteine, reduced L-glutathione, mercaptoethanol and dimethylaminoethanethiol), and their use as fluorescent probes for chromium(VI) ions. The results show that Cr(VI) ions can be ultrasensitively detected with CdTe NCs capped with dimethylaminoethanethiol (DMAET), with high selectivity over Cr(III) and other ions. Synchronous fluorescence spectroscopy was applied to quantify trace levels of Cr(VI) ions with this probe in the 3.0 nM to 0.2 μM concentration range, with a detection limit as low as 0.57 nM. The interaction between the nanocrystals and Cr(VI) ions was investigated in a study on the zeta potentials, UV-Vis absorption spectroscopy and time-resolved luminescence spectroscopy. Electron transfer process occurred and the decay times of the probe remain constant (about 14 ns). This simple and ultrasensitive analytical method was successfully applied to the direct determination of Cr(VI) in spiked samples of environmental waters.

Response to “Critical Growth Temperature of Aqueous CdTe Quantum Dots is Non‐negligible for their Application as Nanothermometers”

SmallVolume 9, Issue 19 p. 3198-3200 Correspondence Response to “Critical Growth Temperature of Aqueous CdTe Quantum Dots is Non-negligible for their Application as Nanothermometers” Laura Martinez Maestro, Laura Martinez Maestro Fluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, SpainSearch for more papers by this authorCarlos Jacinto, Carlos Jacinto Grupo de Fotônica e Fluidos Complexos, Instituto de Física, Universidade Federal de Alagoas. 57072–970, Maceio-AL, BrazilSearch for more papers by this authorUeslen Rocha Silva, Ueslen Rocha Silva Grupo de Fotônica e Fluidos Complexos, Instituto de Física, Universidade Federal de Alagoas. 57072–970, Maceio-AL, BrazilSearch for more papers by this authorFiorenzo Vetrone, Fiorenzo Vetrone Institut National de la Recherche, Scientifique–Énergie Matériaux et Télécommunications, Université du Québec Varennes, QC J3X 1S2, CanadaSearch for more papers by this authorJohn A. Capobianco, John A. Capobianco Department of Chemistry and Biochemistry, Concordia University, Montreal, QC H4B 1R6, CanadaSearch for more papers by this authorDaniel Jaque, Corresponding Author Daniel Jaque daniel.jaque@uam.es Fluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, SpainFluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, Spain.Search for more papers by this authorJosé García Solé, José García Solé Fluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, SpainSearch for more papers by this author Laura Martinez Maestro, Laura Martinez Maestro Fluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, SpainSearch for more papers by this authorCarlos Jacinto, Carlos Jacinto Grupo de Fotônica e Fluidos Complexos, Instituto de Física, Universidade Federal de Alagoas. 57072–970, Maceio-AL, BrazilSearch for more papers by this authorUeslen Rocha Silva, Ueslen Rocha Silva Grupo de Fotônica e Fluidos Complexos, Instituto de Física, Universidade Federal de Alagoas. 57072–970, Maceio-AL, BrazilSearch for more papers by this authorFiorenzo Vetrone, Fiorenzo Vetrone Institut National de la Recherche, Scientifique–Énergie Matériaux et Télécommunications, Université du Québec Varennes, QC J3X 1S2, CanadaSearch for more papers by this authorJohn A. Capobianco, John A. Capobianco Department of Chemistry and Biochemistry, Concordia University, Montreal, QC H4B 1R6, CanadaSearch for more papers by this authorDaniel Jaque, Corresponding Author Daniel Jaque daniel.jaque@uam.es Fluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, SpainFluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, Spain.Search for more papers by this authorJosé García Solé, José García Solé Fluorescence Imaging Group, Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28047 Madrid, SpainSearch for more papers by this author First published: 21 July 2013 https://doi.org/10.1002/smll.201300569Citations: 2Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume9, Issue19October 11, 2013Pages 3198-3200 RelatedInformation

Photoluminescence Stability of Colloidal CdTe Quantum Dots in Various Buffer Solutions

Mercaptoacetic acid-capped CdTe quantum dots (QDs) are potential luminescent markers for biological analysis. The photoluminescence (PL) stability of the QDs in buffer solutions determines their practicability as markers in electrophoresis. The stability of the QDs was thus investigated in electrophoresis buffers including tris–borate–ethylenediaminetetraacetic acid (TBE) and tris–acetate–ethylenediaminetetraacetic acid (TAE). The QDs were completely unstable in high-concentrated buffers (≥0.1×). In the case of low concentrations (≤0.07× for TAE, ≤0.035× for TBE), the PL intensity of the QDs in two kinds of buffers decreased with increasing buffer concentrations. A red-shifted PL peak wavelength and PL intensity fluctuation were observed after dispersing the QDs in diluted TAE buffer solutions with concentrations of ≤0.07× for long time. According to the Stern–Volmer plots of PL degradation, the factors leading to the degradation were complicated, which was attributed to the actions of the components including tris, borate or acetic acid, and ethylenediaminetetraacetic acid as well as their mutual effects.

Bright core-shell semiconductor quantum wires.

Colloidal CdTe quantum wires are reported having ensemble photoluminescence efficiencies as high as 25% under low excitation-power densities. High photoluminescence efficiencies are achieved by formation of a monolayer CdS shell on the CdTe quantum wires. Like other semiconductor nanowires, the CdTe quantum wires may contain frequent wurtzite-zinc-blende structural alternations along their lengths. The present results demonstrate that the optical properties, emission-peak shape and photoluminescence efficiencies, are independent of the presence or absence of such structural alternations.

Size Dependence of the Exciton Transitions in Colloidal CdTe Quantum Dots

In this paper, we present a detailed investigation of the size dependence of the optical transitions of colloidal CdTe QDs ranging in diameter from 2.9 to 14.8 nm. The energy integrated absorption cross section per CdTe unit is investigated in detail for the lowest two exciton transitions (1S3/2(h)–1S(e) and 2S3/2(h)–1S(e)) and shown to increase with decreasing size, although the size dependence of the 2S3/2(h)–1S(e) is less pronounced. The experimental absorption spectra are compared to spectra calculated by using a tight-binding approach. The calculations were carried out with electron–hole configuration interaction (CI) and without (single-particle, SP). The optical absorption spectra calculated by using the CI approach are in excellent agreement with the experiment, as well as the evolution of the optical gap and the optical transitions with nanocrystal size.

Facile Synthesis of Single-sized Colloidal CdTe Assemblies Exhibiting Bright Band Gap Photoemission

Abstract A facile synthetic strategy to prepare single-sized colloidal CdTe assemblies with bright band gap emission is described in this letter. In contrast to traditional approaches, the preparation of trioctylphosphine telluride (TOPTe) was not required for this synthesis, and our approach follows a one-step reaction. The CdTe magic-sized quantum dot (MSQD) assemblies were sequentially grown in this approach, and the thermodynamic equilibrium of CdTe MSQDs sequential growth was proposed.

Hybrid organic/inorganic semiconductor nanostructures with highly efficient energy transfer

Using electro-static assembly of complementary organic (cyanine dye) and inorganic (quantum dots) building blocks we report on formation of an advanced nanohybrid system with highly efficient nonradiative energy transfer properties. In contrast to previous approaches, formation of J-aggregates in cyanine dye solution was triggered by direct injection of as-synthesized colloidal CdTe quantum dots without any additional surface treatment. The optical properties of formed hybrid aggregates have been investigated by absorption and photoluminescence spectroscopy and fluorescence lifetime imaging microscopy. A quantum dot/J-aggregate system shows the enhanced absorption in visible and ultraviolet parts of the spectrum typical of quantum dots, along with the narrow emission linewidth and fast recombination rate characteristic of the J-band emitters. These quantum dot/J-aggregate hybrid systems may have applications in light harvesting systems with the extended spectral absorption as well as optical sensors and optoelectronic devices.

Semiconductor nanowires self-assembled from colloidal CdTe nanocrystal building blocks: optical properties and application perspectives

Solution-based self-assembly of quasi-one-dimensional semiconductor nanostructures (nanowires) from quasi-zero-dimensional (quantum dots) colloidal nanocrystal building blocks has proven itself as a powerful and flexible preparation technique. Polycrystalline CdTe nanowires self-assembled from light-emitting thiol-capped CdTe nanocrystals are the focus of this Feature Article. These nanowires represent an interesting model system for quantum dot solids, where electronic coupling between the individual nanocrystals can be optically accessed and controlled. We provide a literature-based summary of the formation mechanism and the morphology-related aspects of self-assembled CdTe nanowires, and highlight several fundamental and application-related optical properties of these nanostructures. These include fundamental aspects of polarization anisotropies in photoluminescence excitation and emission, the electronic coupling between individual semiconductor nanocrystals constituting the nanowires, and more applied, waveguiding properties of CdTe nanowire bundles and anti-Stokes photoluminescence in a prototypical structure of co-axial nanowires. The optical properties of self-assembled CdTe nanowires considered here render them potential candidates for photonic nano-scale devices.

Facile Synthesis of Straight and Branched CdTe Nanowires Using CdO as Precursor

High-quality colloidal CdTe nanowires (NWs) containing both straight and branched ones were controllably prepared via a solution-based approach, using a low melting Bi nanoparticles as catalysts, CdO and tributylphosphine telluride (TBP-Te) as precursors, and a tri-n-octylphosphine oxide/tri-n-octylphosphine (TOPO/TOP) mixture as solvent. The resulting straight CdTe NWs have typical diameters below 20 nm accompanying with lengths exceeding 10 microm. In the case of branched CdTe NWs, tripod, V-shaped and y-shaped morphologies are obtained by decreasing the apparent Cd/Te molar ratio. It is found that, as the surface capping ligands, di-n-octylphosphinic acid (DOPA) is superior to decylphosphonic acid (DPA) in the reproducible growth of high-quality CdTe NWs. Since highly toxic dimethylcadmium, a cadmium precursor widely used in literatures, is replaced by CdO and the amount of the TOPO/TOP solvent mixture is significantly reduced, a relative safe and economical synthetic approach of high-quality colloidal CdTe NWs with controllable morphology is thus presented.

Colloidal nanoplatelets with two-dimensional electronic structure

The syntheses of strongly anisotropic nanocrystals with one dimension much smaller than the two others, such as nanoplatelets, are still greatly underdeveloped. Here, we demonstrate the formation of atomically flat quasi-two-dimensional colloidal CdSe, CdS and CdTe nanoplatelets with well-defined thicknesses ranging from 4 to 11 monolayers. These nanoplatelets have the electronic properties of two-dimensional quantum wells formed by molecular beam epitaxy, and their thickness-dependent absorption and emission spectra are described very well within an eight-band Pidgeon-Brown model. They present an extremely narrow emission spectrum with full-width at half-maximum less than 40 meV at room temperature. The radiative fluorescent lifetime measured in CdSe nanoplatelets decreases with temperature, reaching 1 ns at 6 K, two orders of magnitude less than for spherical CdSe nanoparticles. This makes the nanoplatelets the fastest colloidal fluorescent emitters and strongly suggests that they show a giant oscillator strength transition.

3D Assembly of Semiconductor and Metal Nanocrystals: Hybrid CdTe/Au Structures with Controlled Content

A 3D metal ion assisted assembly of nanoparticles has been developed. The approach relies on the efficient complexation of cadmium ions and 5-mercaptomethyltetrazole employed as the stabilizer of both colloidal CdTe and Au nanoparticles. It enables in a facile way the formation of hybrid metal-semiconductor 3D structures with controllable and tunable composition in aqueous media. By means of critical point drying, these assemblies form highly porous aerogels. The hybrid architectures obtained are characterized by electron microscopy, nitrogen adsorption, and optical spectroscopy methods.

External Electric Field Effects on State Energy and Photoexcitation Dynamics of Water-Soluble CdTe Nanoparticles

External electric field effects on absorption and photoluminescence (PL) spectra of colloidal CdTe nanoparticles have been measured in a poly(vinyl alcohol) (PVA) film. The electroabsorption spectr...

Photoabsorption and Resonance Energy Transfer Phenomenon in CdTe−Protein Bioconjugates: An Insight into QD−Biomolecular Interactions

Luminescent quantum dots (QDs) possess unique photophysical properties, which are advantageous in the development of new generation robust fluorescent probes based on Forster resonance energy transfer (FRET) phenomena. Bioconjugation of these QDs with biomolecules create hybrid materials having unique photophysical properties along with biological activity. The present study is aimed at characterizing QD bioconjugates in terms of optical behavior. Colloidal CdTe QDs capped with 3-mercaptopropionic acid (MPA) were conjugated to different proteins by the carbodiimide protocol using N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC) and a coupling reagent like N-hydroxysuccinimide (NHS). The photoabsorption of these QD-protein bioconjugates demonstrated an effective coupling of electronic orbitals of constituents. A linear variation in absorbance of bioconjugates at 330 nm proportionate to conjugation suggests a covalent attachment as confirmed by gel electrophoresis. A red shift in the fluorescence of bovine serum albumin (BSA) due to conjugation inferred a decrease in Stokes shift and solvent polarization effects on protein. A proportionate quenching in BSA fluorescence followed by an enhancement of QD fluorescence point toward nonradiative dipolar interactions. Further, reduction in photobleaching of BSA suggests QD-biomolecular interactions. Bioconjugation has significantly influenced the photoabsorption spectrum of QD bioconjugates suggesting the formation of a possible protein shell on the surface of QD. The experimental result suggests that these bioconjugates can be considered nanoparticle (NP) superstructures for the development of a new generation of robust nanoprobes.

Phonon Raman spectra of colloidal CdTe nanocrystals: effect of size, non-stoichiometry and ligand exchange

Resonant Raman study reveals the noticeable effect of the ligand exchange on the nanocrystal (NC) surface onto the phonon spectra of colloidal CdTe NC of different size and composition. The oleic acid ligand exchange for pyridine ones was found to change noticeably the position and width of the longitudinal optical (LO) phonon mode, as well as its intensity ratio to overtones. The broad shoulder above the LO peak frequency was enhanced and sharpened after pyridine treatment, as well as with decreasing NC size. The low-frequency mode around 100 cm-1 which is commonly related with the disorder-activated acoustical phonons appears in smaller NCs but is not enhanced after pyridine treatment. Surprisingly, the feature at low-frequency shoulder of the LO peak, commonly assigned to the surface optical phonon mode, was not sensitive to ligand exchange and concomitant close packing of the NCs. An increased structural disorder on the NC surface, strain and modified electron-phonon coupling is discussed as the possible reason of the observed changes in the phonon spectrum of ligand-exchanged CdTe NCs.PACS: 63.20.-e, 78.30.-j, 78.67.-n, 78.67.Bf

Single-mode waveguiding in bundles of self-assembled semiconductor nanowires

We report on waveguiding in bundles of parallel oriented semiconductor nanowires, self-assembled from colloidal CdTe nanocrystals in solution at room temperature. Individual bundles, as narrow as 170 nm, act as single-mode, subwavelength waveguides for red visible light. Losses are dominated by reabsorption and allow waveguiding over distances of micrometers. This renders self-assembled NW bundles candidates for low-cost, short-distance optical interconnects in hybrid electronic-photonic circuits.

Energy transfer in colloidal CdTe quantum dot nanoclusters

Quantum dot (QD) nanoclusters were formed using oppositely charged colloidal CdTe QDs, of two different sizes, mixed in aqueous solutions. The photoluminescence (PL) spectra and time-resolved PL decays show signatures of Förster resonant energy transfer (FRET) from the donor QDs to the acceptor QD in the nanoclusters. A concentration dependence of the donor QD lifetime is observed in mixed solutions with a donor: acceptor ratio greater than 1:1. The concentration dependent time-resolved PL data indicate different regimes of cluster formation, with evidence for donor-to-donor FRET in the larger donor-acceptor nanoclusters and evidence for the formation of all-donor clusters in mixed solutions with high donor concentrations.

Size-Dependent Multiexciton Spectroscopy and Moderate Temperature Dependence of Biexciton Auger Recombination in Colloidal CdTe Quantum Dots

Size-dependent emission properties of multiexcitons such as the biexciton and the 1S1S1P triexciton were examined in colloidal CdTe quantum dots (QDs) capped with oleic acid and trioctylphosphine (OA/TOP) by time-resolved luminescence spectroscopy. The biexciton and the 1S1S1P triexciton binding energy can be obtained from the spectral shift of the multiexciton emission. The binding energy of CdTe QDs is larger than that of CdSe QDs, possibly due to the stronger confinement of the CdTe QDs. The size dependence of the biexciton luminescence dynamics is comparable to that of biexciton Auger recombination examined by transient absorption spectroscopy. It strongly suggests that the biexciton dynamics is dominated by Auger recombination. On the other hand, the size dependence of the 1P dynamics is different from that of the tendency for the biexciton. The 1P emission dynamics is dominated by the dynamics of the 1S1S1P triexciton, which might be the reason of the different size dependences of the biexciton and ...

Growth and optical characterization of colloidal CdTe nanoparticles capped by a bifunctional molecule

Thiol-capped CdTe nanoparticles were synthesized in aqueous solution by wet chemical route. CdTe nanoparticles with bifunctional molecule mercaptoacetic acid as a stabilizer were synthesized at pH≈11.2 and using potassium tellurite as tellurium source. The effect of refluxing time on the preparation of these samples was measured using UV–vis absorption and photoluminescence analysis. By increasing the refluxing time the UV–vis absorption and photoluminescence results show that the band edge emission is redshifted. The synthesized thiol-capped CdTe were characterized with FT-IR, TEM and TG-DTA. The particle size was calculated by the effective mass approximation (EMA). The role of precursors, their composition, pH and reaction procedure on the development of nanoparticles are analyzed.

Two-photon absorption of quantum dots in the regime of very strong confinement: size and wavelength dependence

The frequency-degenerate two-photon absorption (TPA) in glutathione-capped colloidal CdTe quantum dots with a dot radius ranging from 1.5 to 2 nm, which belongs to the regime of very strong quantum confinement, is determined unambiguously by utilizing the Z-scan technique with femtosecond laser pulses. At laser wavelengths between 720 and 950 nm, the TPA cross sections are measured to be of the order of 10−47-10−46 cm4 s photon−1, with precise values depending on both the laser wavelength and the dot size. The TPA measurements are in agreement with theoretical modeling based on a spherical eight-band Pidgen and Brown model. The quantitative modeling reveals underlying factors that contribute to both the TPA-size relationship and size dispersion effects.