Evolutionary Optimized, Monocrystalline Gold Double Wire Gratings as a Novel SERS Sensing Platform.

Achieving reliable and quantifiable performance in large-area surface-enhanced Raman spectroscopy (SERS) substrates poses a formidable challenge, demanding signal enhancement while ensuring response uniformity and reproducibility. Conventional SERS substrates often made of inhomogeneous materials with random resonator geometries, resulting in multiple or broadened plasmonic resonances, undesired absorptive losses, and uneven field enhancement. These limitations hamper reproducibility, making it difficult to conduct comparative studies with high sensitivity.

From sensing interactions to controlling the interactions: a novel approach to obtain biological transistors for specific and label-free immunosensing.

Antibody-antigen interactions are shaped by the solution pH level, ionic strength, and electric fields, if present. In biological field-effect transistors (BioFETs), the interactions take place at the sensing area in which the pH level, ionic strength and electric fields are determined by the Poisson-Boltzmann equation and the boundary conditions at the solid-solution interface and the potential applied at the solution electrode. The present study demonstrates how a BioFET solution electrode potential affects the sensing area double layer pH level, ionic strength, and electric fields and in this way shapes the biological interactions at the sensing area.

Ab Initio Study of Octane Moiety Adsorption on H- and Cl-Functionalized Silicon Nanowires.

Using first-principles calculations based on density functional theory, we investigated the effects of surface functionalization on the energetic and electronic properties of hydrogenated and chlorinated silicon nanowires oriented along the <112> direction. We show that the band structure is strongly influenced by the diameter of the nanowire, while substantial variations in the formation energy are observed by changing the passivation species. We modeled an octane moiety absorption on the (111) and (110) surface of the silicon nanowire to address the effects on the electronic structure of the chlorinated and hydrogenated systems.

Binding Capabilities of Different Genetically Engineered pVIII Proteins of the Filamentous M13/Fd Virus and Single-Walled Carbon Nanotubes.

Binding functional biomolecules to non-biological materials, such as single-walled carbon nanotubes (SWNTs), is a challenging task with relevance for different applications. However, no one has yet undertaken a comparison of the binding of SWNTs to different recombinant filamentous viruses (phages) bioengineered to contain different binding peptides fused to the virus coat proteins. This is important due to the range of possible binding efficiencies and scenarios that may arise when the protein's amino acid sequence is modified, since the peptides may alter the virus's biological properties or they may behave differently when they are in the context of being displayed on the virus coat protein; in addition, non-engineered viruses may non-specifically adsorb to SWNTs.

Semiconductivity Transition in Silicon Nanowires by Hole Transport Layer.

The surface of nanowires is a source of interest mainly for electrical prospects. Thus, different surface chemical treatments were carried out to develop recipes to control the surface effect. In this work, we succeed in shifting and tuning the semiconductivity of a Si nanowire-based device from n- to p-type.

The non-stationary case of the Maxwell-Garnett theory: growth of nanomaterials (2D gold flakes) in solution.

The solution-based growth mechanism is a common process for nanomaterials. The Maxwell-Garnett theory (for light-matter interactions) describes the solution growth in an effective medium, homogenized by a mean electromagnetic field, which applies when materials are in a stationary phase. However, the charge transitions (inter- and intra-transitions) during the growth of nanomaterials lead to a non-stationary phase and are associated with time-dependent permittivity constant transitions (for nanomaterials).

Systematic Surface Phase Transition of Ag Thin Films by Iodine Functionalization at Room Temperature: Evolution of Optoelectronic and Texture Properties.

We show a simple room temperature surface functionalization approach using iodine vapour to control a surface phase transition from cubic silver (Ag) of thin films into wurtzite silver-iodid (β-AgI) films. A combination of surface characterization techniques (optical, electronical and structural characterization) reveal distinct physical properties of the new surface phase. We discuss the AgI thin film formation dynamics and related transformation of physical properties by determining the work-function, dielectric constant and pyroelectric behavior together with morphological and structural thin film properties such as layer thickness, grain structure and texture formation.

Electronic Properties of Si-Hx Vibrational Modes at Si Waveguide Interface.

Attenuated total reflectance (ATR) and X-ray photoelectron spectroscopy in suite with Kelvin probe were conjugated to explore the electronic properties of Si-Hx vibrational modes by developing Si waveguide with large dynamic detection range compared with conventional IR. The Si 2p emission and work-function related to the formation and elimination of Si-Hx bonds at Si surfaces are monitored based on the detection of vibrational mode frequencies. A transition between various Si-Hx bonds and thus related vibrational modes is monitored for which effective momentum transfer could be demonstrated.

Functionalization of Silver Nanowires Surface using Ag-C Bonds in a Sequential Reductive Method.

Silver nanowires (Ag-NW) assembled in interdigitated webs have shown an applicative potential as transparent and conducting electrodes. However, upon integration in practical device designs, the presence of silver oxide, which instantaneously forms on the Ag-NW surfaces in ambient conditions, is unwanted. Here, we report on the functionalization of Ag-NWs with 4-nitrophenyl moieties through A-C bonds using a versatile two step reduction process, i.

Role of silicon nanowire diameter for alkyl (chain lengths C₁-C₁₈) passivation efficiency through Si-C bonds.

The effect of silicon nanowire (Si NW) diameter on the functionalization efficiency as given by covalent Si-C bond formation is studied for two distinct examples of 25 ± 5 and 50 ± 5 nm diameters (Si NW25 and Si NW50, respectively). A two-step chlorination/alkylation process is used to connect alkyl chains of various lengths (C1-C18) to thinner and thicker Si NWs. The shorter the alkyl chain lengths, the larger the surface coverage of the two studied Si NWs.

Optical nano-structuring in light-sensitive AgCl-Ag waveguide thin films: wavelength effect.

Irradiation of photosensitive thin films results in the nanostructures formation in the interaction area. Here, we investigate how the formation of nanostructures in photosensitive waveguide AgCl thin films, doped by Ag nanoparticles, can be customized by tuning the wavelength of the incident beam. We found, silver nanoparticles are pushed towards the interference pattern minima created by the interference of the incident beam with the excited TE-modes of the AgCl-Ag waveguide.

Kinetic study of H-terminated silicon nanowires oxidation in very first stages.

Oxidation of silicon nanowires (Si NWs) is an undesirable phenomenon that has a detrimental effect on their electronic properties. To prevent oxidation of Si NWs, a deeper understanding of the oxidation reaction kinetics is necessary. In the current work, we study the oxidation kinetics of hydrogen-terminated Si NWs (H-Si NWs) as the starting surfaces for molecular functionalization of Si surfaces.

Early stages of oxide growth in H-terminated silicon nanowires: determination of kinetic behavior and activation energy.

Silicon nanowires (Si NWs) terminated with hydrogen atoms exhibit higher activation energy under ambient conditions than equivalent planar Si(100). The kinetics of sub-oxide formation in hydrogen-terminated Si NWs derived from the complementary XPS surface analysis attribute this difference to the Si-Si backbond and Si-H bond propagation which controls the process at lower temperatures (T < 200 °C). At high temperatures (T≥ 200 °C), the activation energy was similar due to self-retarded oxidation.

Tuning the electrical properties of Si nanowire field-effect transistors by molecular engineering.

Exposed facets of n-type silicon nanowires (Si NWs) fabricated by a top-down approach are successfully terminated with different organic functionalities, including 1,3-dioxan-2-ethyl, butyl, allyl, and propyl-alcohol, using a two-step chlorination/alkylation method. X-ray photoemission spectroscopy and spectroscopic ellipsometry establish the bonding and the coverage of these molecular layers. Field-effect transistors fabricated from these Si NWs displayed characteristics that depended critically on the type of molecular termination.

Silicon nanowires terminated with methyl functionalities exhibit stronger Si-C bonds than equivalent 2D surfaces.

Silicon nanowires (Si NWs) terminated with methyl functionalities exhibit higher oxidation resistance under ambient conditions than equivalent 2D Si(100) and 2D Si(111) surfaces having similar or 10-20% higher initial coverage. The kinetics of methyl adsorption as well as complementary surface analysis by XPS and ToF SIMS attribute this difference to the formation of stronger Si-C bonds on Si NWs, as compared to 2D Si surfaces. This finding offers the possibility of functionalising Si NWs with minimum effect on the conductance of the near-gap channels leading towards more efficient Si NW electronic devices.