Aluminum Doping Effect on Surface Structure of Silver Ultrathin Films

Ultrathin silver films with low loss in the visible and near-infrared spectrum range have been widely used in the fields of metamaterials and optoelectronics. In this study, Al-doped silver films were prepared by the magnetron sputtering method and were characterized by surface morphology, electrical conductivity, and light transmittance analyses. Molecular dynamics simulations and first-principles density functional theory calculations were applied to study the surface morphologies and migration pathway for the formation mechanisms in Al-doped silver films. The results indicate that the migration barrier of silver on a pristine silver surface is commonly lower than that of an Al-doped surface, revealing that the aluminum atoms in the doping site decrease the surface mobility and are conducive to the formation of small islands of silver. When the islands are dense, they coalesce into a single layer, leading to a smoother surface. This might be the reason for the observably lower 3D growth mode of silver on an Al-doped silver surface. Our results with electronic structure insights on the mechanism of the Al dopants on surface morphologies might benefit the quality control of the silver thin films.

Ordering a rhenium catalyst on Ag(001) through molecule-surface step interaction

Atomic scale studies of the anchoring of catalytically active complexes to surfaces may provide valuable insights for the design of new catalytically active hybrid systems. In this work, the self-assembly of 1D, 2D and 3D structures of the complex fac-Re(bpy)(CO)3Cl (bpy = 2,2′-bipyridine), a CO2 reduction catalyst, on the Ag(001) surface are studied by a combination of low-temperature scanning tunneling microscopy and density functional theory calculations. Infrared and sum frequency generation spectroscopy confirm that the complex remains chemically intact under sublimation. Deposition of the complexes onto the silver surface at 300 K leads to strong local variations in the resulting surface coverage on the nanometer scale, indicating that in the initial phase of deposition a large fraction of the molecules is desorbing from the surface. Low coverage regions show a decoration of step edges aligned along the crystal’s symmetry axes <110>. These crystallographic directions are found to be of major importance to the binding of the complexes to the surface. Moreover, the interaction between the molecules and the substrate promotes the restructuring of surface steps along these directions. Well-aligned and decorated steps are found to act as nucleation point for monolayer growth (2D) before 3D growth starts.

In-Situ Detection of Fluid Media Based on Three-Dimensional Dendritic Silver Surface-Enhanced Raman Scattering Substrate

In this paper, a highly active surface enhanced Raman scattering (SERS) substrate based on three-dimensional (3D) dendritic silver nanostructure was constructed in microfluidic channel by one-step electrodisplacement reaction for in-situ...

Self-Organized Fractal Structures on Plasma-Exposed Silver Surface

Planar fractal microstructure is observed on the silver film treated by positive corona discharge for the first time. Due to the abundant positive ions driven by the electrical field of positive polarity, surface modification is mainly induced by the plasma oxidation effect, resulting in a large scale of dendritic pattern with self-similarity and hierarchy. In contrast, negative ions dominate the plasma-film interaction under negative corona discharge condition, leading to a different surface morphology without fractal characteristics. A growth model based on the modified diffusion-limited aggregation (DLA) theory is proposed to describe the formation of the dendritic fractal structure, whilst the physics behind is attributed to the electric field directed diffusion of the positive ions around the surface roughness. Numerical simulation verifies the high density of the hot spot in the dendritic pattern, which may enable potential applications in fractal photonic metamaterials.

Ubiquity

From its invention to the internet age, photography has been considered universal, pervasive, and omnipresent. This anthology of essays posits how the question of when photography came to be everywhere shapes our understanding of all manner of photographic media. Whether looking at a portrait image on the polished silver surface of the daguerreotype, or a viral image on the reflective glass of the smartphone, the experience of looking at photographs and thinking with photography is inseparable from the idea of ubiquity—that is, the apparent ability to be everywhere at once. While photography’s distribution across cultures today is undeniable, the insidious logics and pervasive myths that have governed its spread demand our critical attention, now more than ever.

Ubiquity

From its invention to the internet age, photography has been considered universal, pervasive, and omnipresent. This anthology of essays posits how the question of when photography came to be everywhere shapes our understanding of all manner of photographic media. Whether looking at a portrait image on the polished silver surface of the daguerreotype, or a viral image on the reflective glass of the smartphone, the experience of looking at photographs and thinking with photography is inseparable from the idea of ubiquity—that is, the apparent ability to be everywhere at once. While photography’s distribution across cultures today is undeniable, the insidious logics and pervasive myths that have governed its spread demand our critical attention, now more than ever.

Sensitivity Optimization of Plain Silver Surface Plasmon Resonance Imaging Sensor

Plain silver surface plasmon resonance imaging (SPRi) sensor has been studied extensively due to its high sensitivity and desirable stability in liquid environments. To further enhance sensitivity performance of the sensor, angular sensitivity, angular slope and depth-width ratio (DWR) of SPR curve, and imaging sensitivity are evaluated at different thickness combinations of the gold and silver films respectively. In this work, the angular slope of SPR curve is found to be the critical factor to the optimized imaging sensitivity of plain silver SPRi sensor. In the comparative study, the above parameters of the plain silver SPR sensor, single gold film and bimetallic SPRi sensors are compared. Plain silver SPRi sensor is proved to be of the highest imaging sensitivity, which is 4.08 and 1.18 times imaging sensitivity of the single gold film and bimetallic SPRi sensors separately.

Attachment of Single-Stranded DNA to Certain SERS-Active Gold and Silver Substrates: Selected Practical Tips

Layers formed from single-stranded DNA on nanostructured plasmonic metals can be applied as “working elements” in surface–enhanced Raman scattering (SERS) sensors used to sensitively and accurately identify specific DNA fragments in various biological samples (for example, in samples of blood). Therefore, the proper formation of the desired DNA layers on SERS substrates is of great practical importance, and many research groups are working to improve the process in forming such structures. In this work, we propose two modifications of a standard method used for depositing DNA with an attached linking thiol moiety on certain SERS-active structures; the modifications yield DNA layers that generate a stronger SERS signal. We propose: (i) freezing the sample when forming DNA layers on the nanoparticles, and (ii) when forming DNA layers on SERS-active macroscopic silver substrates, using ω-substituted alkanethiols with very short alkane chains (such as cysteamine or mercaptopropionic acid) to backfill the empty spaces on the metal surface unoccupied by DNA. When 6-mercapto-1-hexanol is used to fill the unoccupied places on a silver surface (as in experiments on standard gold substrates), a quick detachment of chemisorbed DNA from the silver surface is observed. Whereas, using ω-substituted alkanethiols with a shorter alkane chain makes it possible to easily form mixed DNA/backfilling thiol monolayers. Probably, the significantly lower desorption rate of the thiolated DNA induced by alkanethiols with shorter chains is due to the lower stabilization energy in monolayers formed from such compounds.