Fine Surface Structure Research Articles

Nanoscale morphology imaging for arbitrary surfaces by optical coherence tomography

The imaging of nanoscale morphology using optical methods on arbitrary surfaces poses challenges, particularly in the presence of large axial distances and irregular shapes. In this work, we introduce a novel nano-resolution imaging method along the longitudinal direction, utilizing optical coherence tomography (OCT) to measure arbitrary surface morphology comprehensively. Based on the sparsity of the primary profile, our approach allows the adjustment of parameters such as the asymmetric penalty function ϕ, the regularization parameters αi and a high-pass filter to accommodate the micro-structure of any arbitrary surface. Remarkably, our method achieves an exceptional spatial resolution of 3.04 nm. The technique has been validated by observing the surface morphology of spherical and aspherical lenses with nanometer resolution in the longitudinal direction. With the ability to detect impurities and scratches with a height of tens of nanometers, this method can be used to study the fine structure of complex surfaces. This makes it an ideal choice for experimental requirements demanding high-resolution imaging and a broad en-face perspective.

Advanced Interferometry with 3-D Structured Illumination Reveals the Surface Fine Structure of Complex Biospecimens.

Interference reflection microscopy (IRM) is a powerful, label-free technique to visualize the surface structure of biospecimens. However, stray light outside a focal plane obscures the surface fine structures beyond the diffraction limit (dxy ≈ 200 nm). Here, we developed an advanced interferometry approach to visualize the surface fine structure of complex biospecimens, ranging from protein assemblies to single cells. Compared to 2-D, our unique 3-D structure illumination introduced to IRM enabled successful visualization of fine structures and the dynamics of protein crystal growth under lateral (dx-y ≈ 110 nm) and axial (dx-z ≤ 5 nm) resolutions and dynamical adhesion of microtubule fiber networks with lateral resolution (dx-y ≈ 120 nm), 10 times greater than unstructured IRM (dx-y ≈ 1000 nm). Simultaneous reflection/fluorescence imaging provides new physical fingerprints for studying complex biospecimens and biological processes such as myogenic differentiation and highlights the potential use of advanced interferometry to study key nanostructures of complex biospecimens.

Oxidatively modified carbon as a promising material for gold extraction

In this work, we prepare a material termed oxidatively modified carbon (OMC), which significantly outperforms commercial activated carbon products available on the gold mining market. The intriguingly high sorption efficiency of OMC is explained by the graphene oxide (GO) like fine chemical structure of the particles' surface. At the same time, OMC can be easily prepared from readily available carbon sources by wet chemistry protocols with the cost of production ~10 lower than that for GO. The particulate structure of OMC allows simple separation from the used-up solutions. Addition of ammonia to the gold-cyanide solution, additionally boosts sorption capacity of OMC. The developed material can be used in gold mining industry as a sorbent, which can potentially increase the efficiency of the gold extraction process.

Illusory optical defocus generated by shaded surface texture

The human visual system is tasked with the problem of extracting information about the world from images that contain a conflated mixture of environmental sources and optical artifacts generated by the focal properties of our eyes. In most contexts, our brains manage to distinguish these sources, but this is not always the case. Recent work showed that shading gradients generated by smooth three-dimensional (3D) surfaces can elicit strong illusory percepts of optical defocus1,2 - the perception of illusory blur is only eliminated when the surface appears attached to self-occluding contours3, surface discontinuities1, or sharp specular reflections1,2, which all generate sharp ('high spatial frequency') image structure. This suggests that it should also be possible to eliminate the illusory blur elicited by shaded surfaces by altering the surface geometry to include small-scale surface relief, which would also generate high-frequency image structure. We report the surprising result here that this manipulation fails to eliminate the perception of blur; the fine texture fails to perceptually 'bind' to the low-frequency image structure when there is a sufficient gap between the spatial scales of the fine and coarse surface structure. These findings suggest that discontinuous 'gaps' in the spatial scale of textures are a segmentation cue the visual system uses to extract multiple causes of image structure.

A SCANNING ELECTRON MICROSCOPY STUDY OF POLLEN GRAINS

A simple, quick and non-destructive method of preparing fresh pollen grains for scanning electron microscopy (SEM) studies was used in this investigation. The pollen grains of seven taxa belonging to seven families were studied six were dicots, namely Delonix regia, Helianthus annuus, Justicia spicigera,Kigeliaafricana,Lagerstroemia speciosaand Portulaca umbraticola,and one a monocotHymenocallis littoralis. Fresh pollen grains were dehydrated in acidified 2, 2-dimethoxypropane (DMP) followed by criticalpoint drying in carbon dioxide (CO2). In the preliminary study the acidified DMP treated pollen grains were mounted in glycerine and observed under the light microscope. The DMP direct method preserves the original shape of the pollen grains and dissolves the pollen coat thereby enabling observation of the surface ornamentation of the exine. The high magnifications of the SEM provided detailed information about the fine structure or micromorphology of the pollen surface. In the taxa studied the pollen are aperturate and are shed as monads.Among the taxa studied, P.umbraticola was apolar, H.littoralis was heteropolar,and the remaining five were isopolar. The exine was reticulate in D. regia, H.littoralis, J.spicigera, and K.africana echinate in H. annuusandP.umbraticola andfossulate, perforate in L. speciosa.

Relationships between composite roughness and Streptococcus mutans biofilm depth under shear in vitro

ObjectiveTo investigate the effect of substrate, surface roughness, and hydraulic residence time (HRT) on Streptococcus mutans biofilms growing on dental composites under conditions relevant to the oral cavity. MethodsDental composites were prepared with varying amounts of polishing and incubated in a CDC bioreactor with an approximate shear of 0.4 Pa. S. mutans biofilms developed in the bioreactors fed sucrose or glucose and at 10-h or 40-h HRT for one week. Biofilms were characterized by confocal laser microscopy (CLM). Composite surface roughness was characterized by optical profilometry, and pre- and post-incubation composite surface fine structure and elemental composition were determined using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). ResultsPolishing had a significant impact on surface roughness, varying by a factor of 15 between the polished samples and the unpolished control. S. mutans biofilms grew statistically significantly thicker on the unpolished composites. Biofilm thickness was greater at shorter 10-h HRT compared to 40-h HRT. In most cases, biofilm thickness was not statistically significantly greater in sucrose-fed bioreactors than in glucose-fed bioreactors. SEM-EDS analysis did not identify any significant change in elemental composition after aging. ConclusionsAccurate characterization of oral cavity biofilms must consider shear forces and the use of techniques that minimize alteration of the biofilm structure. Under shear, surface smoothness is the most important factor determining S. mutans biofilm thickness followed by HRT, while sucrose presence did not result in significantly greater biofilm thickness. Clinical SignificanceThe obvious patterns of S. mutans growth along sub-micron scale grooving created by the polishing process suggested that initial biofilm attachment occurred in the shear-protected grooves. These results suggest that fine polishing may help prevent the initial formation of S. mutans biofilms compared to unpolished/coarse polished composites.

Revealing surface fine structure on PtAu catalysts by anin situATR-SEIRAS CO-probe method

Anin situATR-SEIRAS CO-probe method is used to identify surface active sites and clarify structure–activity relationship of PtAu catalystsviasecond-derivative spectrum method and Gaussian fitting of infrared spectra of CO oxidation reaction.

Dual functionalized Ni substitution in shuttle-like In2O3 enabling high sensitivity NH3 detection

Hetero-atom doping is an effective way to improve the sensing performance of metal oxide semiconductor gas sensors. However, the synergistic effects generated from hetero-atom substitution in In2O3 lattice and the relationship between the fine surface structure and sensing performance is still ambiguous. Here, Ni substitution in shuttle-like In2O3 nanoparticles have been successfully synthesized, and the materials are fabricated as gas sensor to detect ammonia, which is a toxic molecule that is harmful for human healthy. We find the 2 wt% Ni-doped In2O3 NPs exhibit high sensitivity (Ra/Rg = 2569.42 towards 50 ppm NH3 at 140 °C), achieving 34 folds improvement compared with pristine In2O3 NPs. The sensor also shows good long-term stability, high selectivity and fast response/recovery (23/10 s). Detail structural analysis illustrate the substitution of Ni in rh-In2O3 phase and surface O−(ad) species neighboring the substitution sites are recognized as the active sites, and the reactive oxygen species and surface Bronster acidity can be dramatically enhanced after Ni modification, which contribute to the improvement of sensing performance. Our work illustrate the synergistic effects of hetero-atom doping on the sensing performance and pave the way for design of high performance sensing materials.

Improved maceration techniques to study the fruit vascular anatomy of grape

The visualization and evaluation of fruit vascular bundles in grape are indispensable for understanding the development and growth of the fruit. The vascular bundles in grape are as thin as human hair, and strongly adhere to flesh cells, making it difficult to isolate individual intact vessel elements. Currently there is little information about methods to characterize grape vascular tissue. In this study, we describe an easy and effective technique to visualize the xylem cell structure of the ‘Red Globe’ grape (Vitis L.). The intact vascular bundles of the grape were isolated through enzymatic degradation of flesh cells by hydrolases which were effective in removing flesh cells from vascular bundles. This enabled the illustration of the fine surface structure of vessel elements and their arrangement in the vascular bundles of the grape. This modified method to separate the vascular bundles into individual vessel elements was more effective than former methods of manually shaking to isolate individual vessels. Clear images of xylem vessel arrangement and structural characteristics of individual vessel element were acquired by light microscopy (BX51, Olympus, Tokyo, Japan), transmission electron microscopy (Tecnai 12, Philips, Netherlands) and scanning electron microscopy (GeminiSEM 300, Carl Zeiss, Germany). In addition, the 3D structure of vessel elements was observed using confocal laser scanning microscopy (Zeiss: model: LSM-880, Oberkochen, Germany). The imaging techniques for visualizing and analyzing the structure of xylem vessels in grape described in this study are an improvement of past methods. An effective method to isolate grape vascular bundles from flesh cells was also developed, which enables the imaging of the fine surface structure of vessel elements and their arrangement in grape vascular bundles. By adjusting the process of maceration of vascular bundles, an easy and effective method was developed to gently disrupt the plant tissue and isolate individual vessel elements. These improved techniques are suitable to observe the intact morphology of vascular bundles in the grape, improve experimental efficiency and accelerate new discoveries on the anatomical structure of the grape.

GPU-Accelerated Computation of EM Scattering of a Time-Evolving Oceanic Surface Model II: EM Scattering of Actual Oceanic Surface

Based on marine environmental factors of different sea areas, a high-performance sea clutter time series modeling algorithm for the real sea surface is developed to study the amplitude mean and Doppler spectrum characteristics of sea clutter. The European Centre for Medium-Range Weather Forecasts (ECMWF) data set (ERA-Interim) and ESA’s soil moisture and ocean salinity (SMOS) data set are utilized to establish databases of different marine environmental factors. Combined with the mixed spectrum model, the geometric fine structure of wind-driven sea surface with swell superposition is established by using the double-superposition method (DSM) and comprehensively considering small-scale capillary ripples, large-scale gravity waves and swell. A triangle facet-based sea clutter series modeling algorithm is developed, in which the quasi-specular scattering based on a triangle and the scattering based on gravity wave modulation capillary spectrum are calculated, respectively, and compared with the measured results. For high-resolution radar, dynamic sea surface modeling and sea clutter calculation are very time consuming. In this paper, the Tesla K80 GPU manufactured by NVIDIA in Santa Clara, Computed Unified Device architecture (CUDA) high-performance parallel technology and some optimization strategies are adopted to improve the efficiency of sea clutter modeling. The results can be used to analyze the distribution characteristics of marine factors, the average amplitude and Doppler characteristics of sea clutter in different sea areas.

Unravelling the surface structure and active site of CaSnO3, as well as H2O2 formation mechanism in two electron water oxidation reaction

The two-electron water oxidation reaction (2e-WOR) is an eco-friendly process to produce H2O2, which attracts much attention due to its low cost and high safety. CaSnO3 is a potential industrial catalyst for 2e-WOR reaction with high performance. However, the surface structure and active site of CaSnO3, as well as H2O2 formation mechanism, are still unknown due to its complex structure and limitation of characterization technique in resolution of surface fine structure and intermediates. To solve this difficult problem, the authors systematically investigated the surface structures of CaSnO3 and the adsorption and reaction behaviors of H2O, OH and H2O2 on CaSnO3 by density functional theory method. The present work indicated that the O4(Sn) surface with 5-coordinated Sn is the most stable termination of CaSnO3(121) by comparing the surface energies of 17 terminations of CaSnO3(121); OH strongly chemisorbs at the top site of Sn on CaSnO3(121) and can diffuse on surface with the free energy barrier of 0.68 ∼ 1.07 eV; the coordination unsaturated Sn atom is the active site for OH adsorption and H2O2 formation. According to the deep understanding of the mechanism of the 2e-WOR reaction to H2O2 on CaSnO3, two practical ways were proposed to design and develop 2e-WOR catalysts with high performance.

Simulating intergrowth formation in zeolite crystals: impact on habit and functionality.

A kinetic Monte-Carlo methodology is presented for simulating crystal growth in materials which contain stacking faults. By simulating a large number of potential growth and dissolution events, a representation of the crystal is generated at various stages throughout the crystallisation, allowing the effects of disorder on the evolution of crystal habit and nanoscale surface topography to be explored. As examples, simulations were performed on two intergrown zeolite materials - zeolite T and zeolite beta. In both zeolite T and zeolite beta, simulations demonstrate how an intergrown structure leads to a characteristic roughening of certain crystal facets. In zeolite beta, this is accompanied by the development of internal defects which shows a non-homogeneous distribution. Results of simulations are validated by direct comparison to experimental scanning electron microscopy, atomic force microscopy and X-ray diffraction data. All simulations are performed using the CrystalGrower software package with modifications to account for disorder and should be generally applicable to all classes of crystals.

Exploration of Metal-Molecule interaction of subnanometric heterogeneous catalysts via simulated Raman spectrum

To date, using either state-of-the-art direct image or indirect spectroscopic techniques to simultaneously identify the surface fine structure of heterogeneous catalyst and predict the chemical state of surface species under operando conditions, particularly down to subnanometry and even atomic scale, remains a substantial challenge. Nevertheless, reducing the size of the heterogeneous catalyst from bulk down to atomic level, the spectroscopic characteristics responsible for the unique interaction between metal and adsorbed molecules will thereby be tuned, giving rise to non-coherent spectroscopic characteristics for even the same metal/molecule combination, as repeatedly witnessed in literatures. This work details a new chemical strategy to identify the tangling characteristics of Raman spectra derived from the subnanometric cluster and even single atom catalysts under reactive atmosphere, a long-standing issue that impeded the further implementation of Raman techniques in miniaturized heterogeneous catalysis. We illustrate this concept through the use of a density functional theory (DFT) approach to simulate the Raman spectra of three typical Ptx/CeO2 (x = 1, 2, 9) systems of increasing sizes which represent isolated atom, layered clusters, and multiple layer clusters, respectively, under CO atmosphere to acquire the spectroscopic characteristics, usually masked by multiple interferences from the inevitable CO/Pt interaction circulated in relevant experimental studies. The novel approach explored in this manuscript should open up a new avenue for the use of theoretical chemistry method as a general tool to complement the current experimental method in identifying the intrinsic spectroscopic features masked by multiple interferences originated from complex chemical environment.

Interaction of surfactants with barley leaf surfaces: time-dependent recovery of contact angles is due to foliar uptake of surfactants

Main conclusionTime-dependent contact angle measurements of pure water on barley leaf surfaces allow quantifying the kinetics of surfactant diffusion into the leaf.Barley leaf surfaces were sprayed with three different aqueous concentrations (0.1, 1.0 and 10%) of a monodisperse (tetraethylene glycol monododecyl ether) and a polydisperse alcohol ethoxylate (BrijL4). After 10 min, the surfactant solutions on the leaf surfaces were dry leading to surfactant coverages of 1, 10 and 63 µg cm−2, respectively. The highest surfactant coverage (63 µg cm−2) affected leaf physiology (photosynthesis and water loss) rapidly and irreversibly and leaves were dying within 2–6 h. These effects on leaf physiology did not occur with the lower surfactant coverages (1 and 10 µg cm−2). Directly after spraying of 0.1 and 1.0% surfactant solution and complete drying (10 min), leaf surfaces were fully wettable for pure water and contact angles were 0°. Within 60 min (0.1% surfactant) and 6 h (1.0% surfactant), leaf surfaces were non-wettable again and contact angles of pure water were identical to control leaves. Scanning electron microscopy investigations directly performed after surfactant spraying and drying indicated that leaf surface wax crystallites were partially or fully covered by surfactants. Wax platelets with unaltered microstructure were fully visible again within 2 to 6 h after treatment with 0.1% surfactant solutions. Gas chromatographic analysis showed that surfactant amounts on leaf surfaces continuously disappeared over time. Our results indicate that surfactants, applied at realistic coverages between 1 and 10 µg cm−2 to barley leaf surfaces, leading to total wetting (contact angles of 0°) of leaf surfaces, are rapidly taken up by the leaves. As a consequence, leaf surface non-wettability is fully reappearing. An irreversible damage of the leaf surface fine structure leading to enhanced wetting and increased foliar transpiration seems highly unlikely at low surfactant coverages of 1 µg cm−2.

Biochemical evidence of epicuticular wax compounds involved in cotton-whitefly interaction.

Sucking insects require a surface of plants on which the legs and the eggs of insects will adhere and to which insect mouthparts will access. The primary plant protection against insects is their surface property, which hinders the attachment of the insect’s legs and eggs. The epicuticular waxes chemistry influences the fine structure of the cuticular surface. In current study, an attempt was made to investigate the variation of chemical compounds in epicuticular waxes of four cotton species that classify them resistant or susceptible i.e., Gossypium abroreum, G. hirsutum, G. arboreum wax deficient mutant (GaWM3) and G. harknessi which were evaluated for their interaction with whitefly and CLCuV transmission. Gossypium hirsutum an insect and CLCuV susceptible cotton variety, was found to have four compounds namely Trichloroacetic acid, hexadecylester, P-xylenolpthalein, 2-cyclopentene-1-ol, 1-phenyl-and Phenol, 2,5-bis [1,1- dimethyl] which could interact with chitin of whitefly while only two compounds in Gossypium arboreum an insect and CLCuV resistant cotton variety could interact with chitin of whitefly. Similarly, GaWM3 and Gossypium harkasnessi were found to have only a single compound. Number of whiteflies found on leaves of G. hirsutum was much higher as compared to other cotton species. Keeping this fact in mind a wax biosynthetic gene CER3, from Arabidopsis thaliana was transformed into G. hirsutum and the plants were evaluated for their resistance against whitefly and CLCuV transmission. In microscopic analysis transgenic plants clearly showed higher amounts of leaf waxes as compared to non-transgenics. The least whitefly population and CLCuV titer of <10,000 units was found in transgenic plants compared to non-transgenic cotton where it was ≈4.5X106 units that confirmed the role of wax in insect interaction and ultimately to CLCuV transmission. This study provides novel insight on wax related compounds involved in cotton-whitefly interaction, which potentially can help in developing more efficient control strategies for this destructive pest.

Study of the parameters of the pure iron structure after surface plastic deformation treatment with a complex-profile tool

The structure of pure iron after surface plastic deformation (SPD) by a multiradius roller (MR-roller) was studied using optical microscopy (OM) and atomic force microscopy (AFM). An optical microscope of reflected light is used to study the size and uniformity of grains and subgrains (Neophot-21). The fine structure of the sample surface was studied using an atomic force microscope (Solver PH47-PRO) contact method. The paper shows changes in the deformation relief of the material after processing with an MR-roller.

Microstructure and Mechanical Properties of Nickel-Based Coatings Fabricated through Laser Additive Manufacturing

In this study, single-layer and three-layer nickel-based coatings were fabricated on 316L SS by laser additive manufacturing. The phase characterization, microstructure observation, and microhardness analysis of the coatings were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), and microhardness tester. And the wear resistance of the coatings was analyzed through dry sliding friction and wear test. The results show that the cross-section microstructure of the three-layer nickel-based coating is different from that of the single-layer one under the influence of heat accumulation; the dendrite structure in the central region of the former is equiaxial dendrite, while that of the latter still remains large columnar dendrites. The existence of solid solution phase γ-(Fe, Ni) and hard phases of Ni17Si3, Cr5B3, Ni3B in the coating significantly improve the wear resistance of the coating, and the microhardness is nearly 2.5 times higher than that of the substrate. However, the average microhardness of multilayer cladding coating is about 48 HV0.2 higher than that of the single-layer cladding coating. In addition, the fine surface structure of the three-layer nickel-based coating improves the wear resistance of the coating, making this coating with the best wear resistance.

Image-Based Measurement of Structural Color using Spectral Camera

We perceive structural colors by optical phenomena such as light interference and diffraction caused by a fine structure of the object surface. One of the characteristics of structural colors is that a wavelength distribution of light changes depending on an incident angle of a light source and a viewing angle. Generally, for color evaluation and reproduction, it is required to acquire reflection characteristics of objects. Therefore, BRDF (Bidirectional Reflectance Distribution Function) is often used as a function that represents reflection characteristics depending on incident and viewing angles. In this study, we measured BRDF of structural colors based on a method to acquire image-based material reflection characteristics using a spectral camera. The measurement was performed by aligning an optical axis of a spectral camera with a structural color sample and changing an irradiation angle of a light source. Reflection characteristics were represented by using a radiance factor, which was a ratio between a spectral radiance of white material and that of structural color. From measurement results, we confirmed an angle-dependent radiance factor. Finally, based on a measured spectral radiance of a structural color sample, we spectrally reproduced the structural color using a spectral projector based on model fitting of spectral data.

High Efficiency Electrochemical Degradation of Phenol Using a Ti/PbO2-Bi-PTh Composite Electrode

A novel Ti/PbO2-Bi-PTh composite electrode was successfully prepared by electrodeposition and applied in electrochemical degradation of phenol. The Ti/PbO2-Bi-PTh electrode was characterized by XRD, SEM, AFM, LSV, CV and EIS. Results showd that the electrode has a fine and compact surface structure, higher oxygen evolution potential (OEP, 2.42 V) and low charge transfer resistance (51.00 Ω). The electrode also exhibited excellent electrochemical oxidation activity on the degradation of phenol (1000 mg l−1) with degradation efficiency of 100% and TOC removal rate of 93.58% achieved in 60 min and 180 min, respectively. In addition, possible mechanism of phenol degradation on the electrode was proposed by analyzing the intermediate products with GC-MS. Noticeably, the Ti/PbO2-Bi-PTh electrode displayed excellent stability and high electrocatalytic performance after 10 cycles, indicating its promising application in the phenolic wastewater treatment.

Joining of Metal to Ceramic Plate Using Super-Spread Wetting

Ceramic-metal composites with novel performance are desirable materials; however, differences in their properties result in difficulties in joining. In this study, the joining of metal to ceramic is investigated. We recently succeeded in causing super-spread wetting on the surface fine crevice structures of metal surfaces produced by both laser irradiation and reduction-sintering of oxide powders. In this work, joining copper onto an Al2O3 plate was achieved by taking advantage of super-spread wetting. Fe2O3 powder was first sintered under reducing conditions to produce a microstructure which can cause super-spread wetting of liquid metal on an Al2O3 plate. A powder-based surface fine crevice structure of metallic iron with high porosity was well-formed due to the bonding of the reduced metallic iron particles. This structure was joined on an Al2O3 plate with no cracking by the formation of an FeAl2O4 layer buffering the mismatch gap between the thermal expansion coefficients of iron and Al2O3. We successfully achieved metalizing of the Al2O3 surface with copper without interfacial cracks using super-spread wetting of liquid copper through the sintered metallic iron layer on the Al2O3 plate. Then, laser irradiation was conducted on the surface of the copper-metalized Al2O3 plate. A laser-irradiated surface fine crevice structure was successfully created on the copper-metalized Al2O3 plate. Moreover, it was confirmed that the super-spread wetting of liquid tin occurred on the laser-irradiated surface fine crevice structure, finally accomplishing the joining of a copper block and the copper-metalized Al2O3.