Controllable conversion of plasmonic Cu2-xS nanoparticles to Au2S by cation exchange and electron beam induced transformation of Cu2-xS-Au2S core/shell nanostructures (original) (raw)
Related papers
Electronic Changes Induced by Surface Modification of Cu2–xS Nanocrystals
The Journal of Physical Chemistry C, 2015
Copper sulfide nanocrystals (Cu 2−x S NCs) consisting of earth-abundant and nontoxic elements have attracted attention for optoelectronic and plasmonic applications due to their tunable light absorption and emission properties. In this work, we present a study of the electronic changes induced in organic-capped Cu 2−x S NCs by surface modification treatments using charge transport and optical spectroscopy measurements. We have investigated surface treatments yielding ligand exchange and also ligand removal as well as changes in electronic defect density. The structural and morphological changes induced by the treatments were monitored by infrared spectroscopy, electron microscopy, and electron paramagnetic resonance. Untreated Cu 2−x S NCs exhibit a strong absorption band arising from a localized surface plasmon resonance (LSPR). We found that using a ligand exchange procedure (ethanedithiol treatment), the electrical conductivity in films of Cu 2−x S NCs can be enhanced by 5 orders of magnitude, while maintaining other electronic properties of the individual NCs like optical absorption and LSPR. The improvements in the electrical conductivity were attributed to the reduction of the inter-NC separation in the films, as revealed by the structural and morphological studies. We also have observed that ligand removal treatments such as thermal annealing and hydrazine treatment yield a LSPR red-shift, while the electrical conductivity increases by up to 5 and 7 orders of magnitude, respectively. We proposed a model for the surface reactions taking place during these treatments. Our work highlights the potential of simple chemical or thermal treatments in tailoring the electronic properties of Cu 2−x S NCs, making thermally treated Cu 2−x S NCs interesting for tunable plasmonic and optoelectronic applications.
Nanochemistry Research, 2016
Here we present our experimental results in synthesizing Au-Cu nano-particles with tunable localized surface plasmon resonance frequency through wet-chemical at temperature room. The reaction is performed in the presence of ascorbic acid as a reducing agent and polyvinyl pyrrolidone as capping agent via four different procedures: (1) mixture of 90% HAuCl4 and 10% CuSO4.5H2O precursors, (2) mixture of 75% HAuCl4 and 25% CuSO4.5H2O precursors, (3) mixture of 50% HAuCl4 and 50% CuSO4.5H2O precursors (4) mixture of 25% HAuCl4 and 75% CuSO4.5H2O precursors. Effect of different percentages of Cu on Au nanoparticles has been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM with EDAX analysis), DRS UV-Vis, and Fourier transform IR spectra (FTIR) analysis. X-ray diffraction (XRD) analysis revealed that the nanoparticles are of cubic structure without an impure phase. The successful doping of the Cu into the Au host was evident by XRD line shiftings. The increasing percentage of copper leads to the decreasing grain size. With the increase of Cu2+ to Au3+ ratio in the Cu2+/Au3+ mixed solution (> 50% Cu), XRD lines show no shifting. The average crystal sizes of the particles at room temperature were less than 9.9 nm. The surface plasmon resonance peak shifts from 380 to 340 nm, party due to the change in particle size. SEM images show a spherical shape and the size of nanoparticles becomes smaller with increasing the percentage of copper. Moreover, in the molar ratio of Cu2+/Au3+ = 75/25 (>50% Cu), mixture of spherical and trigonal nanoparticles were prepared. Fourier transform infrared spectroscopy (FT-IR) showed the coordination and conjugation nanoparticles with N and O atoms of C-N and C=O bonds.
Au-core, Au3Cu-alloyed shell nanoparticles passivated with CuS2 were fabricated by the polyol method, and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au3Cu alloyed shell surrounded by CuS2 surface layer. X-ray diffraction measurements and results from numerical simulations confirm these findings. From the atomic resolution micrographs, we identified edge dislocations at the twin boundaries of the particles, as well as evidence of the diffusion of Cu atoms into the Au region, and the reordering of the lattice on the surface, close to the vertices of the particle. These defects will impact the atomic and electronic structures, thereby changing the physical and chemical properties of the nanoparticles. On the other hand, we show for the first time the formation of an ordered superlattice of Au3Cu and a self-capping layer made using one of the alloy metals. This has significant consequences on the physical mechanism that form multicomponent nanoparticles.
Langmuir, 2013
Au-core, Au 3 Cu-alloyed shell nanoparticles passivated with CuS 2 were fabricated by the polyol method, and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au 3 Cu alloyed shell surrounded by CuS 2 surface layer. X-ray diffraction measurements and results from numerical simulations confirm these findings. From the atomic resolution micrographs we identified edge dislocations at the twin boundaries of the particles, as well as evidence of the diffusion of Cu atoms into the Au region, and the reordering of the lattice on the surface, close to the vertices of the particle. These defects will impact the atomic and electronic structures thereby changing the physical and chemical properties of the nanoparticles. On the other hand we show for the first time the formation of an ordered superlattice of Au 3 Cu and a self-capping layer made using one of the alloy metals. This has significant consequences on the physical mechanism that form multi component nanoparticles.
Journal of the American Chemical Society, 2009
Cu 2-x S (x ) 1, 0.2, 0.03) nanocrystals were synthesized with three different chemical methods: sonoelectrochemical, hydrothermal, and solventless thermolysis methods in order to compare their common optical and structural properties. The compositions of the Cu 2-x S nanocrystals were varied from CuS (covellite) to Cu 1.97 S (djurleite) through adjusting the reduction potential in the sonoelectrochemical method, adjusting the pH value in the hydrothermal method and by choosing different precursor pretreatments in the solventless thermolysis approach, respectively. The crystallinity and morphology of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), which shows that most of them might be of pure stoichiometries but some of them are mixtures. The obtained XRDs were studied in comparison to the XRD patterns of previously reported Cu 2-x S. We found consistently that under ambient conditions the copper deficient Cu 1.97 S (djurleite) is more stable than Cu 2 S (chalcocite). Corroborated by recent computational studies by Lambrecht et al. and experimental work by Alivisatos et al. This may be the reason behind the traditionally known instability of the bulk Cu 2 S/CdS interface. Both Cu 2 S and the copper-deficient Cu 1.97 S have very similar but distinguishable electronic and crystal structure. The optical properties of these Cu 2-x S NCs were characterized by UV-vis spectroscopy and NIR. All presented Cu 2-x S NCs show a blue shift in the band gap absorption compared to bulk Cu 2-x S. Moreover the spectra of these Cu 2-x S NCs indicate direct band gap character based on their oscillator strengths, different from previously reported experimental results. The NIR spectra of these Cu 2-x S NCs show a carrier concentration dependent plasmonic absorption.
Journal of Applied Crystallography
Temperature-programmed in situ X-ray diffraction with whole-powder-pattern modeling is used to investigate the reaction of Au@Cu2O core–shell nanoparticles to form nanocrystalline bimetallic Cu x Au1−x alloys (x = 0, 0.25, 0.5, 0.75, 1.0) in a reducing atmosphere. The mechanisms of the reactions are key to informed design of tailored non-equilibrium nanostructures for catalytic and plasmonic materials. The Au@Cu2O reaction is initiated by reduction of the Cu2O cuprite shell to form nanocrystalline metallic Cu at about 413 K. Alloying begins immediately upon formation of metallic Cu at 413 K, with the nucleation of an Au-rich alloy phase which reaches the nominal Cu content of the overall system stoichiometry by 493 K. All bimetallic alloys form a transient ordered Cu3Au intermetallic compound at intermediate temperatures, with the onset of ordering and subsequent disordering varying by composition. No evidence for an ordered Au3Cu intermetallic is found for any composition. Signific...
Nano Letters, 2020
We report a heterometallic seed-mediated synthesis method for monodisperse penta-twinned Cu 2 nanorods using Au nanocrystals as seeds. Elemental analyses indicate that resultant nanorods consist predominantly of copper with a gold content typically below 3 at. %. The nanorod aspect 4 ratio can be readily adjusted from 2.8 to 13.1 by varying the molar ratio between Au seeds and Cu 5 precursor, resulting in narrow longitudinal plasmon resonances tunable from 762 to 2201 nm. 6 Studies of reaction intermediates reveal that symmetry-breaking is promoted by rapid nanoscale 7 diffusion in Au-Cu alloys and the formation of a gold-rich surface. The growth pathway features 8 co-evolving shape and composition whereby nanocrystals become progressively enriched with Cu 9 concomitant with nanorod growth. The availability of uniform colloidal Cu nanorods with widely 10 tunable aspect ratios opens new avenues toward the synthesis of derivative one-dimensional metal 11 nanostructures, and applications in surface-enhanced spectroscopy, bioimaging, electrocatalysis, 12 among others. ASSOCIATED CONTENT 1 Supporting Information. Experimental section, structural characterization of Cu NRs, FDTD 2 simulation results and studies of reaction intermediates are included. This material is available free 3 of charge via the Internet at http://pubs.acs.org.
Summer and Autumn 2016-Cu Nanoparticle
2016
Here we present our experimental results in synthesizing Au-Cu nano-particles with tunable localized surface plasmon resonance frequency through wetchemical at temperature room. The reaction is performed in the presence of ascorbic acid as a reducing agent and polyvinyl pyrrolidone as capping agent via four different procedures: (1) mixture of 90% HAuCl 4 and 10% CuSO 4 .5H 2 O precursors, (2) mixture of 75% HAuCl 4 and 25% CuSO 4 .5H 2 O precursors, (3) mixture of 50% HAuCl 4 and 50% CuSO 4 .5H 2 O precursors (4) mixture of 25% HAuCl 4 and 75% CuSO 4 .5H 2 O precursors. Effect of different percentages of Cu on Au nanoparticles has been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM with EDAX analysis), DRS UV-Vis, and Fourier transform IR spectra (FTIR) analysis. X-ray diffraction (XRD) analysis revealed that the nanoparticles are of cubic structure without an impure phase. The successful doping of the Cu into the Au host was evident by XRD line shiftings...
ACS Nano, 2013
In the realm of semiconductor nanomaterials, a crystal lattice heavily doped with cation/anion vacancies or ionized atomic impurities is considered to be a general prerequisite to accommodating excess free carriers that can support localized surface plasmon resonance (LSPR). Here, we demonstrate a surfactant-assisted nonaqueous route to anisotropic copper sulfide nanocrystals, selectively trapped in the covellite phase, which can exhibit intense, size-tunable LSPR at near-infrared wavelengths despite their stoichiometric, undoped structure. Experimental extinction spectra are satisfactorily reproduced by theoretical calculations performed by the discrete dipole approximation method within the framework of the DrudeÀSommerfeld model. The LSPR response of the nanocrystals and its geometry dependence are interpreted as arising from the inherent metallic-like character of covellite, allowed by a significant density of lattice-constitutional valence-band free holes. As a consequence of the unique electronic properties of the nanocrystals and of their monodispersity, coherent excitation of symmetric radial breathing modes is observed for the first time in transient absorption experiments at LSPR wavelengths.