A stand-alone compact EUV microscope based on gas-puff target source

We report on a very compact desk-top transmission extreme ultraviolet (EUV) microscope based on a laser-plasma source with a double stream gas-puff target, capable of acquiring magnified images of objects with a spatial (half-pitch) resolution of sub-50 nm. A multilayer ellipsoidal condenser is used to focus and spectrally narrow the radiation from the plasma, producing a quasi-monochromatic EUV radiation (λ = 13.8 nm) illuminating the object, while a Fresnel zone plate objective forms the image. Design details, development, characterization and optimization of the EUV source and the microscope are described and discussed. Test object and other samples were imaged to demonstrate superior resolution compared to visible light microscopy. Lay description Developments in nanoscience demand tools capable of capturing images with a nanometer spatial resolution beyond the capability of well-known visible light microscopes. Herein, we present the design details, development, characterization and optimization of a very compact desk-top transmission microscope, operating in invisible to an eye radiation from the so called extreme ultraviolet (EUV) range. The apparatus is based on a laser-plasma source coupled with a special type of objective called Fresnel zone plate. It is capable of acquiring magnified images of objects with a spatial resolution of sub-50 nm, approximately 5–10 times better than the spatial resolution of classical visible light microscopes, in a short acquisition time. The main motivation for development of such compact systems operating with EUV radiations is the possibility to get information about thin samples due to the easily absorption of these radiation by solid materials with very small thicknesses, of the order of about 100 nm. Additionally, the employment of such kind of microscopes might open the possibility to perform experiments without necessity to employ large ‘photon facilities’ such as synchrotrons or free electron lasers and could have a huge impact on the speed of nanotechnology development. Imaging results, concerning nanostructures and biomedical samples, are presented and discussed

Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles

We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles

Revisiting semicontinuous silver films as surface-enhanced Raman spectroscopy substrates

Surface-enhanced Raman spectroscopy (SERS) is a very promising analytical technique for the detection and identification of trace amounts of analytes. Among the many substrates used in SERS of great interest are nanostructures fabricated using physical methods, such as semicontinuous metal films obtained via electron beam physical vapor deposition. In these studies, we investigate the influence of morphology of semicontinuous silver films on their SERS properties. The morphologies studied ranged from isolated particles through percolated films to almost continuous films. We found that films below the percolation threshold (transition from dielectric-like to metal-like) made of isolated silver structures provided the largest SERS enhancement of 4-aminothiophenol (4-ATP) analyte signals. The substrate closest to the percolation threshold has the SERS signal about four times lower than the highest signal sample

Heterogeneous Carbon Gels: N‑Doped Carbon Xerogels from Resorcinol and N‑Containing Heterocyclic Aldehydes

Direct, acid (HCl) initiated sol–gel polycondensation of resorcinol with pyrrole-2-carboxaldehyde or its derivative <i>N</i>-methyl-2-pyrrolecarboxaldehyde yields thermosetting phenolic organic gels with N-content of up to 8.4 wt %. After carbonization, sturdy monoliths of N-doped carbon xerogels with N-content of up to 8 wt % are produced. The morphology and porosity of the doped carbons can be tuned by the solvent composition and the amount of polymerization catalyst used. An increase in carbonization temperature from 600 to 1000 °C strongly affects the carbon gels’ microporosity, resulting in a decrease in N₂ adsorption capacity, but a significant increase in H₂ adsorption capacity (at −196 °C). The growing H₂ sorption capacity with the decreasing specific surface area (measured by N₂) is related to the gradual shrinkage of the carbon xerogel matrix and narrowing of the small micropores. In addition, it is demonstrated that pyridine-based heterocyclic aldehydes, that is, 2- or 4-pyridinecarboxaldehyde, condensate with resorcinol in basic conditions (KOH, NH₄OH). However, in this case, monoliths cannot be produced and powders/rigid solid precipitates are obtained instead. If NH₄OH is used as a sol–gel polycondensation catalyst, N-doped foams are obtained as a final carbonaceous product

Synthesis and characterization of noble metal–titania core–shell nanostructures with tunable shell thickness

Core–shell nanostructures have found applications in many fields, including surface enhanced spectroscopy, catalysis and solar cells. Titania-coated noble metal nanoparticles, which combine the surface plasmon resonance properties of the core and the photoactivity of the shell, have great potential for these applications. However, the controllable synthesis of such nanostructures remains a challenge due to the high reactivity of titania precursors. Hence, a simple titania coating method that would allow better control over the shell formation is desired. A sol–gel based titania coating method, which allows control over the shell thickness, was developed and applied to the synthesis of Ag@TiO2 and Au@TiO2 with various shell thicknesses. The morphology of the synthesized structures was investigated using scanning electron microscopy (SEM). Their sizes and shell thicknesses were determined using tunable resistive pulse sensing (TRPS) technique. The optical properties of the synthesized structures were characterized using UV–vis spectroscopy. Ag@TiO2 and Au@TiO2 structures with shell thickness in the range of ≈40–70 nm and 90 nm, for the Ag and Au nanostructures respectively, were prepared using a method we developed and adapted, consisting of a change in the titania precursor concentration. The synthesized nanostructures exhibited significant absorption in the UV–vis range. The TRPS technique was shown to be a very useful tool for the characterization of metal–metal oxide core–shell nanostructures

Fabrication of silver nanoisland films by pulsed laser deposition for surface-enhanced Raman spectroscopy

The results of studies on the fabrication and characterization of silver nanoisland films (SNIFs) using pulsed laser deposition (PLD) and the evaluation of these films as potential surface-enhanced Raman scattering (SERS) substrates are reported. The SNIFs with thicknesses in a range of 4.7 ± 0.2 nm to 143.2 ± 0.2 nm were deposited under different conditions on silicon substrates. Size and morphology of the fabricated silver nanoislands mainly depend on the substrate temperature, and number and energy of the laser pulses. SERS properties of the fabricated films were evaluated by measuring SERS spectra of para-mercaptoaniline (pMA) molecules adsorbed on them. SERS enhancement factors are shown to depend on the SNIF morphology, which is modified by changes of the deposition conditions. The highest enhancement factor in the range of 105 was achieved for SNIFs that have oval and circular silver nanoislands with small distances between them

On the Factors that Control the Reactivity of Meta-Benzynes

The reactivities of eleven 3,5-didehydropyridinium and six 2,4-didehydropyridinium cations toward cyclohexane were examined in the gas phase by using Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry as well as high-level quantum chemical calculations. The results unequivocally demonstrate that the reactivity of meta-benzyne analogs can be tuned from more radical-like to less radical-like by changing the type and position of substituents. For example, σ-acceptor substituents at the 4-position and π-donor substituents at the 2-position in 3,5-didehydropyridinium cations partially decouple the biradical electrons, which results in lower energy transition states, and faster radical reactions. In contrast, σ-acceptors at the 2-position and π-donors at the 4-position in 3,5-didehydropyridinium cations cause stronger coupling between the biradical electrons, which results in lower radical reactivity. Three main factors are found to control the reactivity of these biradicals: (1) the energy required to distort the minimum energy dehydrocarbon atom separation to the separation of the transition state, (2) the S-T splitting at the separation of the transition state, and (3) the electron affinity at the separation of the transition state. This journal i

Substituent Effects on the Nonradical Reactivity of 4-Dehydropyridinium Cation

Recent studies have shown that the reactivity of the 4-dehydropyridinium cation significantly differs from the reactivities of its isomers toward tetrahydrofuran. While only hydrogen atom abstraction was observed for the 2- and 3-dehydropyridinium cations, nonradical reactions were observed for the 4-isomer. In order to learn more about these reactions, the gas-phase reactivities of the 4-dehydropyridinium cation and several of its derivatives toward tetrahydrofuran were investigated in a Fourier transform ion electron resonance mass spectrometer. Both radical and nonradical reactions were observed for most of these positively charged radicals. The major parameter determining whether nonradical reactions occur was found to be the electron affinity of the radicals-only those with relatively high electron affinities underwent nonradical reactions. The reactivities of the monoradicals are also affected by hydrogen bonding and steric effects

Reactivity of a σ,σ,σ,σ-Tetraradical: The 2,4,6-Tridehydropyridine Radical Cation

The 2,4,6-tridehydropyridine radical cation, an analogue of the elusive 1,2,3,5-tetradehydrobenzene, was generated in the gas phase and its reactivity examined. Surprisingly, the tetraradical was found not to undergo radical reactions. This behavior is rationalized by resonance structures hindering fast radical reactions. This makes the cation highly electrophilic, and it rapidly reacts with many nucleophiles by quenching the N–C <i>ortho</i>-benzyne moiety, thereby generating a relatively unreactive <i>meta</i>-benzyne analogue

Low-voltage anodizing of copper in sodium bicarbonate solutions

The low-voltage (&lt; 5 V) anodization of copper in aqueous solutions of sodium bicarbonate was studied for the first time. As demonstrated, this method leads to the formation of microstructures on a copper surface, that are composed of malachite (CuCO3·Cu(OH)2). Moreover, by tuning the operating conditions, i.e., applied cell voltage and electrolyte concentration, different surface morphologies can be grown. As shown by electron microscopy investigation, clusters of ribbons corrosion pits or nonuniformly located powdery precipitates are formed when the low anodizing voltage is applied. Anodization at 1.0 V in 0.4 M sodium bicarbonate solution led to the formation of a velvet-like, deep black anodic layer that covered the whole metal surface with ribbon-resembling structures. A thorough investigation of the obtained anodic layers with X-ray diffraction (XRD), X-ray adsorption (XAS), Raman, and X-ray Photoelectron Spectroscopy (XPS) uncovered the mixed crystalline-amorphous nature of the anodic copper species. Besides dominating the crystalline malachite phase, the amorphous cupric oxide was also identified. This composition offers promising features for catalytic applications, hence, low-voltage anodized copper was tested in an electrochemical CO2 reduction reaction to explore one possible application of the presented material. The current density of 4.7 mA cm−2 was registered for the selected sample.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Peyman Taher