Dynamics of nanocubes embedding into polymer films investigated: Via spatially resolved plasmon modes

Integration of nanoparticles into thin films is essential for the development of functional materials, studies of fundamental interfacial processes, and exploitation of inherent properties from the particles themselves. In this work, we systematically investigate the process of incorporation of silver nanocubes into thin polystyrene films at temperatures just above the polymer glass transition. The process of nanocrystal incorporation can be precisely monitored via far-field spectroscopy to observe the response of spatially resolved hybrid plasmon modes. Each plasmon resonance has a distinct dynamic range and maximum sensitivity forming a complementary set of nanorulers that operates over a distance comparable to the edge length of the cubes. The approach explored in this work is a general robust method for the development of long-range polychromatic nanorulers

Thermal Decomposition of Copper Iminopyrrolidinate Atomic Layer Deposition (ALD) Precursors on Silicon Oxide Surfaces

The thermal chemistry of Cu(I)-N-sec-butyl-iminopyrrolidinate on silicon oxide films was characterized by using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Three temperature regimes were identified after adsorption at 100 K: (1) molecular desorption at 240 K; (2) protonation of some of the ligands and formation of the corresponding iminopyrrolidine at 300 K; and (3) fragmentation of the remaining ligands to produce H2, HCN, and butene, which occurs concurrently with the reduction of the copper ions. Most of the carbon and nitrogen atoms are removed from the surface after the third step, and copper desorbs above 900 K. Adsorption of the copper complex at room temperature leads to a partial early reduction of the metal and to the extended production of sec-butyl-iminopyrrolidine in two broad peaks around 330 and 460 K. Self-limiting adsorption, as required for atomic layer deposition (ALD) processes, is seen up to 500 K, but by 550 K continuous copper deposition takes place. In general, the chemistry of this copper ALD precursor is milder and cleaner on silicon oxide than on metals

Effect of the nature of the substrate on the surface chemistry of atomic layer deposition precursors

The thermal chemistry of Cu(I)-sec-butyl-2-iminopyrrolidinate, a promising copper amidinate complex for atomic layer deposition (ALD) applications, was explored comparatively on several surfaces by using a combination of surface-sensitive techniques, specifically temperature-programmed desorption and x-ray photoelectron spectroscopy (XPS). The substrates explored include single crystals of transition metals (Ni(110) and Cu(110)), thin oxide films (NiO/Ni(110) and SiO2/Ta), and oxygen-treated metals (O/Cu(110)). Decomposition of the pyrrolidinate ligand leads to the desorption of several gas-phase products, including CH3CN, HCN and butene from the metals and CO and CO2 from the oxygen-containing surfaces. In all cases dehydrogenation of the organic moieties is accompanied by hydrogen removal from the surface, in the form of H2 on metals and mainly as water from the metal oxides, but the threshold for this chemistry varies wildly, from 270 K on Ni(110) to 430 K on O/Cu(110), 470 K on Cu(110), 500 K on NiO/Ni(110), and 570 K on SiO2/Ta. Copper reduction is also observed in both the Cu 2p3/2 XPS and the Cu L3 VV Auger (AES) spectra, reaching completion by 300 K on Ni(110) but occurring only between 500 and 600 K on Cu(110). On NiO/Ni(110), both Cu(I) and Cu(0) coexist between 200 and 500 K, and on SiO2/Ta a change happens between 500 and 600 K but the reduction is limited, with the copper atoms retaining a significant ionic character. Additional experiments to test adsorption at higher temperatures led to the identification of temperature windows for the self-limiting precursor uptake required for ALD between approximately 300 and 450 K on both Ni(110) and NiO/Ni(110); the range on SiO2 had been previously determined to be wider, reaching an upper limit at about 500 K. Finally, deposition of copper metal films via ALD cycles with O2 as the co-reactant was successfully accomplished on the Ni(110) substrate

Anomalous permittivity and plasmon resonances of copper nanoparticle conformal coatings on optical fibers

The conformal coating of a 50 nm-thick layer of copper nanoparticles deposited with pulse chemical vapor deposition of a copper (I) guanidinate precursor on the cladding of a single mode optical fiber was monitored by using a tilted fiber Bragg grating (TFBG) photo-inscribed in the fiber core. The pulse-per-pulse growth of the copper nanoparticles is readily obtained from the position and amplitudes of resonances in the reflection spectrum of the grating. In particular, we confirm that the real part of the effective complex permittivity of the deposited nano-structured copper layer is an order of magnitude larger than that of a bulk copper film at an optical wavelength of 1550 nm. We further observe a transition in the growth behavior from granular to continuous film (as determined from the complex material permittivity) after approximately 20 pulses (corresponding to an effective thickness of 25 nm). Finally, despite the remaining granularity of the film, the final copper-coated optical fiber is shown to support plasmon waves suitable for sensing, even after the growth of a thin oxide layer on the copper surface

Plasmonic properties of copper nanoparticles deposited on tilted fiber bragg gratings

Surface plasmon resonance (SPR) sensors have been widely used in refractive-index related measurements, including label-free bio-chemical sensing, because of their high sensitivity and real-time detection capability. It is well established that noble metals, in particular, gold (Au) and silver (Ag), support plasmon resonances that can be tuned throughout the UV-vis-NIR region. However, the plasmonic properties of Cu have not received much attention as compared to Au and Ag because of oxidation of the Cu surfaces [1]

Thermal chemistry of Cu(I)-iminopyrrolidinate and Cu(I)-guanidinate atomic layer deposition (ALD) precursors on Ni(110) single-crystal surfaces

The thermal chemistry of tetrakis[Cu(I)-N-sec-butyl-iminopyrrolidinate] and bis[Cu(I)-N,N-dimethyl- N', N''-di-iso-propyl-guanidinate], promising precursor for atomic layer deposition (ALD) applications, was investigated on a Ni(110) single-crystal under ultrahigh vacuum (UHV) conditions by using X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). Both precursors, which exist as tetramers and dimers in the solid phase, respectively, undergo dissociative adsorption at temperatures below 200 K to produce adsorbed monomers on the surface. A β-hydride elimination step is then operative near 300 K that leads to the release of some of the ligands in dehydrogenated form. The remaining adsorbates obtained from either precursor undergo similar further decomposition between 350 K and 600 K as the Cu atoms are reduced from a Cu(I) oxidation state to metallic Cu(0). Hydrocarbons resulting from the elimination of the terminal moieties include ethene and acetonitrile from the Cu(I)-iminopyrrolidinate and propene from the Cu(I)-guanidinate, which are ejected at ∼420-490 K, and HCN in both cases at ∼570-580 K. These results shows several similarities with the surface chemistry previously reported for bis[Cu(I)-N,N'-di-sec-butyl-acetamidinate], and they suggest a common behavior in the surface reactions of these families of Cu(I)-amidinate, Cu(I)-iminopyrrolidinate, and Cu(I)-guanidinate ALD precursors

Hybridized plasmon resonances in core/half-shell silver/cuprous oxide nanoparticles

Core/shell nanoparticles are of interest due to their attractive optical, electronic, and catalytic properties. By combining these core/shell features with physical anisotropy of the shell-by selectively capping only a portion of the core-nanostructures with unique properties can be formed. This work presents the synthesis and investigates the plasmonic properties of silver nanocube (AgNC)/cuprous oxide core/half-shell nanoparticles. The developed partial shell growth technique is suitable for any room temperature two-step core/shell synthesis. Using this technique AgNC/Cu2O core/shell nanoparticles were formed with a distinct half-shell morphology, either pyramidal or cubic, where the geometry of the half-shell can be precisely controlled by selecting specific synthesis conditions. Furthermore, the cuprous oxide half-shells induced hybridization of the plasmon modes in the silver core and thus enabled spatial and spectral manipulation of plasmon resonances for nanoparticles in suspension. The proposed core/half-shell morphology will be particularly advantageous for directed assembly, formation of dimers for SERS sensing, or as individual particles for catalysis

Gas-phase thermolysis of a guanidinate precursor of copper studied by matrix isolation, time-of-flight mass spectrometry, and computational chemistry

The fragmentation of the copper(i) guanidinate [Me2NC(N/Pr) 2Cu]2 (1) has been investigated with time-of-flight mass spectrometry (TOF MS), matrix-isolation FTIR spectroscopy (Ml FTIR spectroscopy), and density functional theory (DFT) calculations. Gas-phase thermolyses of 1 were preformed in the temperature range of 100-800 °C. TOF MS and Ml FTIR gave consistent results, showing that precursor 1 starts to fragment at oven temperatures above 150 °C, with a close to complete fragmentation at 260 °C. Precursor 1 thermally fragments to Cu( S), H2(g), and the oxidized guanidine Me 2NC(=N/Pr)(N=CMe2) (3). In TOF MS experiment, 3 was clearly indentifled by its molecular ion at 169.2 u. Whereas H2+ was detected, atomic Cu was not found in gas-phase thermolysis. In addition, the guanidine Me2NC(N/Pr)(NH/Pr) (2) was detected as a minor component among the thermolysis products. Ml thermolysis experiments with precursor 1 were performed, and species evolving from the thermolysis oven were trapped in solid argon at 20 K. These species were characterized by FTIR spectroscopy. The most indicative feature of the resulting spectra from thermolysis above 150 °C was a set of intense and structured peaks between 1600 and 1700 cm-1, an area where precursor 1 does not have any absorbances. The guanldine 2 was matrix-isolated, and a comparison of its FTIR spectrum with the spectra of the thermolysis of 1 indicated that species 2 was among the thermolysis products. However, the main IR bands In the range of 1600 and 1700 cm-1 appeared at 1687.9,1668.9,1635.1, and 1626.6 cm-1 and were not caused by species 2. The oxidized guanldine 3 was synthesized for the first time and characterized by1H NMR and FTIR spectroscopy. A comparison of an FTIR spectrum of matrix isolated 3 with spectra of the thermolysis of 1 revealed that the main IR bands in the range of 1600 and 1700 cm -1 are due to the presence of 3. The isomers exhibit the NMe2 group cis or trans to the /Pr group, with c/s-3 being significantly less stable than trans-3. At higher temperature secondary thermal fragments had been observed. For example at 700 °C, TOF MS and Ml FTIR data showed that species 2 and 3 both eliminate HNMe2 to give the carbodilmides /PrNCNPr (CDI) and /PrNCN[C(=CH 2)Me] (4), respectively. A DFT study of the decomposition of compound 1 was undertaken at the B3LYP/6-31+G(d,p) level of theory employing dispersion-correcting potentials (DCPs). The DFT study rationalized both carb

Study of Monomeric Copper Complexes Supported by N-Heterocyclic and Acyclic Diamino Carbenes

The thermal properties of a series of monomeric copper(I) hexamethyldisilazide complexes supported by N-heterocyclic and acyclic diamino carbenes were evaluated to study the impact of N-alkyl substituents and backbone character on volatility and thermal stability of copper amides. The series of complexes were either liquids or solids with melting points in the broad range of 45-184 °C. Vaporization rates were measured by stepped-isothermal TGA experiments and found to be between 110-170 °C. Enthalpies of vaporization were determined to be 63-90 kJ/mol. Temperatures for 1 Torr vapor pressure were estimated to be 143-172 °C, showing a general dependence on molecular weight. The imidazolylidene complexes were thermally unstable with convincing evidence indicating the unsaturated backbone as a point of weakness. The imidazolinylidene complexes showed excellent thermal stability with comparable results for the formamidinylidenes complexes. The steric parameter of the carbene, %VBur, was calculated for all complexes characterized by single crystal X-ray diffraction