Similar Surface Coverage Research Articles

Pixel-wise Phase Map Fusion Technique for High Dynamic Range 3-D Shape Measurement

Abstract Digital fringe projection technologies have been extensively applied in 3-D shape measurements. However, it is still limited to achieve accurate 3-D reconstruction of high reflective surfaces. To circumvent this problem, we propose a complete framework to realize pixel-by-pixel phase post-compensation of overexposed points, including the construction of hardware system and the guidelines of algorithm design. First, a virtual binocular vision system is established. Second, based on the fundamentals of projective and spatial transformation, three robust algorithms with low computational complexity are devised to generate a fused phase map that overcomes the information loss due to overexposure. Furthermore, experiments are conducted to evaluate the performance of the proposed method. Qualitative experiment results show that the presented technique achieve a similar surface coverage compared with the other two mainstream methods, but is superior to them in terms of measurement efficiency (13 images vs. 144 images, 13 images vs. 32 images). Quantitative experimentation further verifies the feasibility of our method in precise 3-D measurement, with sphere diameter errors of 0.0367mm and 0.0361mm, spherical centroid distance error of 0.0269mm, and plane distance error of 0.0186mm.

Utilization of Spontaneous Alkyne-Gold Self-Assembly Chemistry as an Alternative Method for Fabricating Electrochemical Aptamer-Based Sensors.

Electrochemical aptamer-based (E-AB) sensors are a promising class of biosensors which use structure-switching redox-labeled oligonucleotides (aptamers) codeposited with passivating alkanethiol monolayers on electrode surfaces to specifically bind and detect target analytes. Signaling in E-AB sensors is an outcome of aptamer conformational changes upon target binding, with the sequence of the aptamer imparting specificity toward the analyte of interest. The change in conformation translates to a change in electron transfer between the redox label attached to the aptamer and the underlying electrode and is related to analyte concentration, allowing specific electrochemical detection of nonelectroactive analytes. E-AB sensor measurements are reagentless with time resolutions of seconds or less and may be miniaturized into the submicron range. Traditionally these sensors are fabricated using thiol-on-gold chemistry. Here we present an alternate immobilization chemistry, gold-alkyne binding, which results in an increase in sensor lifetimes under ideal conditions by up to ∼100%. We find that gold-alkyne binding is spontaneous and supports efficient E-AB sensor signaling with analytical performance characteristics similar to those of thiol generated monolayers. The surface modification differs from gold-thiol binding only in the time and aptamer concentration required to achieve similar aptamer surface coverages. In addition, alkynated aptamers differ from their thiolated analogues only by their chemical handle for surface attachment, so any existing aptamers can be easily adapted to utilize this attachment strategy.

The surface edge explorer (SEE): A measurement-direct approach to next best view planning

High-quality observations of the real world are crucial for a variety of applications, including producing 3D printed replicas of small-scale scenes and conducting inspections of large-scale infrastructure. These 3D observations are commonly obtained by combining multiple sensor measurements from different views. Guiding the selection of suitable views is known as the Next Best View (NBV) planning problem. Most NBV approaches reason about measurements using rigid data structures (e.g., surface meshes or voxel grids). This simplifies next best view selection but can be computationally expensive, reduces real-world fidelity and couples the selection of a next best view with the final data processing. This paper presents the Surface Edge Explorer (SEE), a NBV approach that selects new observations directly from previous sensor measurements without requiring rigid data structures. SEE uses measurement density to propose next best views that increase coverage of insufficiently observed surfaces while avoiding potential occlusions. Statistical results from simulated experiments show that SEE can attain similar or better surface coverage with less observation time and travel distance than evaluated volumetric approaches on both small- and large-scale scenes. Real-world experiments demonstrate SEE autonomously observing a deer statue using a 3D sensor affixed to a robotic arm.

Red Vetchling (Lathyrus cicera L.), a Promising Crop for the Sustainable Replacement of Soybean Meal and Reducing the Carbon Footprint of European Aquafeeds.

In fish diets, soybean meal (SBM) is still positioned as the most widely used alternative to replace fishmeal. Red vetchling (Lathyrus cicera), a crop locally produced in Europe, is here evaluated as a substitute for SBM. Rainbow trout (Oncorhynchus mykiss) juveniles (10.34 ± 0.04 g) were fed for 90 days. Six experimental diets replacing the SBM content at 0, 8, 16, 33, 66, and 100% (Named Control, T8, T16, T33, T66, and T100) were tested. Growth performance and fish fillet amino acid composition were only significantly reduced in fish fed the T100 diet. Histopathological analysis showed that no major alterations were observed in the intestine, while T100 fish had a higher density of pyknotic nuclei in the hepatocytes than the Control, but similar hepatocyte surface coverage. Finally, postprandial levels of glucose and triglycerides in blood plasma decreased when red vetchling content was increased, but was only not fully restored after 24 h in the case of glucose in T66 and T100 fish. According to these results, red vetchling meal can replace up to 66% of the SBM without a negative effect on fish growth or physiology, representing a good alternative raw material for reducing European aquaculture's dependency on SBM imports and the carbon footprint of aquafeeds.

Automated Exposures Selection for High Dynamic Range Structured-Light 3-D Scanning

Structured light (SL) scanning has gained widespread applications in industrial metrology; however, measuring objects that have large surface-reflectivity variations is challenging. For this purpose, the high dynamic range (HDR) technique has become a standard method to fuse features under multiple exposures. Presently, in HDR measurement, manual or cumbersome exposure selection strategies are used. This paper reports a new exposure selection approach. An image quality metric is designed to evaluate captured images and suppress regional overexposure, based on which a multiple-exposures selection strategy is developed. Unlike existing methods for single-optimal exposure selection, in our approach, pixel-filtering is introduced to locate eligible pixels and candidate pixels in next exposures. Experimental results with industrial parts having large surface-reflectivity variations demonstrated that compared to HDR with 15 exposures (equal time intervals), our proposed approach achieved a similar surface coverage rates (97.4% vs. 98.1%) and measurement accuracy (0.043 mm vs. 0.041 mm), but only took 3-4 exposures averagely.

Differences in perchlorate adsorption to azobenzene monolayers on gold formed from thioacetate and thiol precursors

Abstract Modification of metal surfaces with complex molecules opens interesting opportunities to build additional functionality into these surfaces. In this work, self assembled monolayers (SAMs) based on the same photoswitchable azobenzene motif but with different head groups have been synthesized and their SAMs on Au(111)/Si substrates have been characterized. 3-[(4-phenylazo)phenoxy]propyl thiol (PAPT) and its acetyl group protected analog, 3-[(4-phenylazo)phenoxy]propyl thioacetate (PAPA), have been synthesized. SAMs from PAPT and PAPA have been characterized by infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ellipsometry and cyclic voltammetry (CV). The SAM-forming units of both SAMs are the same, as confirmed by IR and XPS, and the SAMs have similar surface coverage, as evidenced by analysis of the reductive desorption peaks in CVs. The tilt angle of the azobenzene moiety was ca. 75° with respect to the surface normal as determined by IR spectroscopy, i.e., the molecules are lying quite flat on the gold surface. Despite similar surface coverages, the CVs for PAPT in aqueous perchlorate solution show a typical perchlorate adsorption peak to gold, whereas the corresponding experiments with PAPA show no perchlorate adsorption at all. In conclusion, SAM formation can lead to an increase in the number of electrochemically accessible surface sites on the final, SAM covered surface. Whether the amount of such sites increases or decreases, depends on the precursor. The precursor most likely affects the adsorption mechanism and thus the atomic surface structure of the metal at the metal/SAM interface. Thus, details of the SAM formation mechanism, which is affected by the precursor used, can have quite strong effects on the electrochemical properties, and likely also electrocatalytic properties, of the resulting modified surface.

SCVP: Learning One-Shot View Planning via Set Covering for Unknown Object Reconstruction

The view planning (VP) problem in robotic active vision enables a robot system to automatically perform object reconstruction tasks. Lacking prior knowledge, next-best-view (NBV) methods are typically used to plan a view sequence, with the goal of covering as many object surface areas as possible in an unknown environment. However, such methods have two problems: (1) they are unable to perform global path planning; and (2) the reconstruction process is inefficient because of time-consuming ray casting and high movement cost. We propose a neural network, SCVP, to pre-learn prior knowledge via set covering (SC) based training so as to achieve one-shot view planning. The SCVP network takes the volumetric occupancy grid as input and directly predicts a small (ideally minimum) number of views that cover all surface areas. Given object 3D models as a priori geometric knowledge, the training dataset is automatically labeled by the set covering optimization method. We propose a global path planning method to reconstruct objects without redundant movement. Comparative experiments on multiple datasets of 3D models show that, under the condition of similar or better surface coverage, the proposed method can outperform state-of-the-art NBV methods in terms of movement cost and inference time. Real-world experiments confirm that the proposed method can achieve faster object reconstruction than other methods.

C1q recognizes antigen-bound IgG in a curvature-dependent manner

C1q is an important recognition protein in the complement system, which is a major protein cascade in the innate immune system. Upon recognition of a target by C1q, the target is marked for opsonization and destruction. C1q recognizes many pathogenic patterns directly, but an important target is the Fc domain of antibodies binding to their antigen. In this paper, the curvature-dependence of the interaction between IgG and C1q is studied by surface plasmon resonance and quartz crystal microbalance. IgG is organized in similar surface coverage densities on flat polystyrene surfaces and polystyrene nanoparticles of different sizes, and the amount of C1q binding to the IgG is investigated. Nanoparticles in solution were found to aggregate upon incubation with IgG, and therefore a new technique utilizing nanoparticles binding to antifouling polymer brush functionalized surfaces was used to prepare surfaces with nanoparticles for measurements with surface plasmon resonance. Interestingly antigen-bound IgG at the curved surface of nanoparticles showed 5.6 times lower binding of C1q compared to at matched flat surfaces. There was no significant difference between the binding at 100 and 200 nm polystyrene particles. These findings are important for designing drug delivery systems to evade the complement system.

Host–Guest Interaction at Molecular Interfaces: Cucurbit[7]uril as a Sensitive Probe of Structural Heterogeneity in Ferrocenyl Self-Assembled Monolayers on Gold

Herein, we combine host–guest recognition chemistry and electrochemical analysis to demonstrate that the nanometer-size, supramolecular hosts can be adapted as sensitive probes for structural heterogeneity in organized molecular assemblies on a surface. In particular, we carried out thorough cyclic voltammetric (CV) studies to evaluate the binding of cucurbit[7]uril on mixed ferrocenylundecanethiolate/n-alkanethiolate self-assembled monolayers (SAMs) on gold (FcC11S-/CmS-Au) prepared with different methods (coadsorption vs postassembly exchanges) and with varied diluting n-alkanethiols. On the basis of the distinct CV responses of CB[7]@Fc complex and free Fc on the SAM surfaces, we were able to determine the conversion ratio from Fc to CB[7]@Fc, a direct indication of its overall density and uniformity. We have shown that the FcC11S-/C8S-Au prepared by coadsorption in a binary solution with low mole fraction of FcC11SH (5%) and by exchanging preassembled C8S-Au SAM with FcC11SH for a short time (1 min) has the “ideal” structure with isolated and uniformly distributed Fc groups on the surface. In contrast, with similar Fc surface coverage, the FcC11S-/C8S-Au prepared by exchanging FcC11S-Au with C8SH for a prolonged time (20 h) has clustered and nonuniformly distributed Fc groups at the surface. While consistent with previous observations based on conventional electrochemical or microscopic studies, the present finding expands the capability of host–guest chemistry as a new tool to probe the structures of organized molecular assemblies at the nanometer scale.

Adsorption and Recovery of Polyphenolic Flavonoids Using TiO2-Functionalized Mesoporous Silica Nanoparticles.

Exploiting specific interactions with titania (TiO2) has been proposed for the separation and recovery of a broad range of biomolecules and natural products, including therapeutic polyphenolic flavonoids which are susceptible to degradation, such as quercetin. Functionalizing mesoporous silica with TiO2 has many potential advantages over bulk and mesoporous TiO2 as an adsorbent for natural products, including robust synthetic approaches leading to high surface area, and stable separation platforms. Here, TiO2-surface-functionalized mesoporous silica nanoparticles (MSNPs) are synthesized and characterized as a function of TiO2 content (up to 636 mg TiO2/g). The adsorption isotherms of two polyphenolic flavonoids, quercetin and rutin, were determined (0.05-10 mg/mL in ethanol), and a 100-fold increase in the adsorption capacity was observed relative to functionalized nonporous particles with similar TiO2 surface coverage. An optimum extent of functionalization (approximately 440 mg TiO2/g particles) is interpreted from characterization techniques including grazing incidence X-ray scattering (GIXS), high-resolution transmission electron microscopy (HRTEM), and nitrogen adsorption, which examined the interplay between the extent of TiO2 functionalization and the accessibility of the porous structures. The recovery of flavonoids is demonstrated using ligand displacement in ethanolic citric acid solution (20% w/v), in which greater than 90% recovery can be achieved in a multistep extraction process. The radical scavenging activity (RSA) of the recovered and particle-bound quercetin as measured by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay demonstrates greater than 80% retention of antioxidant activity by both particle-bound and recovered quercetin. These mesoporous titanosilicate materials can serve as a synthetic platform to isolate, recover, and potentially deliver degradation-sensitive natural products to biological systems.

Hydrophobic interaction and patch charge attraction in α-Al2O3 dispersions under the influence of adsorbed low molecular-weight polyacrylic acid sodium salt and poly(methacrylic acid) sodium salt: yield stress and AFM force study

Maximum yield stress data showed that low molecular-weight (Mw) (∼7 kDa) poly(methacrylic acid) sodium salt (PMA-Na) additive at low surface coverage displayed significant patch charge attraction in contrast to polyacrylic acid sodium salt (PAA-Na) additive of similar Mw and surface coverage. Intramolecular hydrophobic interaction between CH3 groups in the polymer molecule during adsorption produced a much more compact patch with a higher negative charge density giving rise to the stronger patch charge attraction. At high surface coverage, intermolecular hydrophobic interaction between CH3 groups on the adsorbed layer of the interacting particles was not observed from maximum yield stress data. Such interaction was, however, observed in AFM force-distance characterization data for interaction between spherical alumina particles and sapphire plates coated with PMA-Na in retraction mode. The compression of the adsorbed layers at contact during the approach mode was postulated to deform and breakup the intramolecular interaction between the CH3 groups and promoted intermolecular interaction between these groups in the layer coating the particle and plate. This resulted in a strong adhesion force seen in the retraction mode after contact at low pH near the point of zero charge.

Controlled graphene oxide assembly on silver nanocube monolayers for SERS detection: dependence on nanocube packing procedure.

Hybrid graphene oxide/silver nanocubes (GO/AgNCs) arrays for surface-enhanced Raman spectroscopy (SERS) applications were prepared by means of two procedures differing for the method used in the assembly of the silver nanocubes onto the surface: Langmuir–Blodgett (LB) transfer and direct sequential physisorption of silver nanocubes (AgNCs). Adsorption of graphene oxide (GO) flakes on the AgNC assemblies obtained with both procedures was monitored by quartz crystal microbalance (QCM) technique as a function of GO bulk concentration. The experiment provided values of the adsorbed GO mass on the AgNC array and the GO saturation limit as well as the thickness and the viscoelastic properties of the GO film. Atomic force microscopy (AFM) measurements of the resulting samples revealed that a similar surface coverage was achieved with both procedures but with a different distribution of silver nanoparticles. In the GO covered LB film, the AgNC distribution is characterized by densely packed regions alternating with empty surface areas. On the other hand, AgNCs are more homogeneously dispersed over the entire sensor surface when the nanocubes spontaneously adsorb from solution. In this case, the assembly results in less-packed silver nanostructures with higher inter-cube distance. For the two assembled substrates, AFM of silver nanocubes layers fully covered with GO revealed the presence of a homogeneous, flexible and smooth GO sheet folding over the silver nanocubes and extending onto the bare surface. Preliminary SERS experiments on adenine showed a higher SERS enhancement factor for GO on Langmuir–Blodgett films of AgNCs with respect to bare AgNC systems. Conversely, poor SERS enhancement for adenine resulted for GO-covered AgNCs obtained by spontaneous adsorption. This indicated that the assembly and packing of AgNCs obtained in this way, although more homogeneous over the substrate surface, is not as effective for SERS analysis.

Oxidation of laccase for improved cathode biofuel cell performances

Graphite rods were modified by substituted aryldiazonium salts allowing subsequent laccase immobilisation and direct electron transfer at the cathode. Two covalent enzyme immobilisation methods were performed with carboxy and amino substituted grafted groups, either via the formation of an amide bond or a Schiff base between the glycosidic groups of the enzyme and the amino groups on the electrode surface, respectively. Laccase adsorption efficiency was consistently compared to the covalent attachment method on the same carbon surface, showing that the latter method led to a higher immobilisation yield when the electrode surface was functionalised with carboxylic groups, as shown from both laccase activity measurement towards an organic reducing substrate, ABTS, and quantitative XPS analysis. Both analytical methods led to similar laccase surface coverage estimations. From activity measurements, when laccase was covalently immobilised on the electrode functionalised with carboxylic groups, the surface coverage was found to be 43±2% whereas it was only 10±3% when laccase was adsorbed. Biocatalysed dioxygen reduction current was also higher in the case of covalent immobilisation. For the first time, oxidised laccase performances were compared to unmodified laccase, showing significant improved efficiency when using oxidised laccase: the current obtained with oxidised laccase was 141±37μAcm−2 compared to 28±6μAcm−2 for unmodified laccase after covalent immobilisation of the enzyme on a graphite electrode functionalised with carboxylic groups.

Evaluating the Performance of 2-Mercapto-5-Benzimidazolesulfonic Acid in Controllable Electro-Healing Cracks in Nickel

Healing or repairing cracks in materials is of significant importance for sustainable development of the world. As the mobility of metal atoms is quite limited at service temperature, it remains a challenge to realize crack healing in metallic materials. Recently, an electrochemical process named electro-healing was introduced to heal cracks in nickel. Meanwhile，it is also recognized that to get a satisfactory recovery of strength, it is critical to minimize pores or voids in the healed crack by controlling the growth mode of healing crystals, which might be realized by the addition of additives to the healing solution. In our recent work, we found that controllable electro-healing cracks was achieved by the addition of polyethyleneimine (PEI) and saccharin to the Watts bath under free convection. Nevertheless, some defects were found along the interface between the substrate and the healing crystals when PEI and saccharin were added to the solution, which might be attributed to the lowered current efficiency. As with the presence of inhibitors, hydrogen evolution, the secondary reaction on the cathode, becomes less ignorable, the definite result of which is the reduction of current efficiency. Hence, additives with relatively higher cathode current efficiency has to be introduced to the controllable electro-healing of cracks. 2-mercapto-5-benzimidazolesulfonic acid (MBIS) has been found to an effective inhibitor in the reduction of nickel. In the present work, different concentration of MBIS was added to conventional Watts bath to systematically evaluate the performance of MBIS in the controllable electro-healing on thin pure Ni plate with a through thickness crack. Voltammograms under different concentration and convection condition were carried out to evaluate the inhibition ability of MBIS to the reduction of nickel. Rotating disk electrode (RDE) with rotation speeds of 50 rpm, 300 rpm and 2000 rpm was employed to assess the convection dependent performance of MBIS. The cathodic current efficiency and surface coverage were examined. These characterizations together with the SEM observation of the healed crack were analyzed to get the correlation between the addition of MBIS and the electro-healing process of crack. It is demonstrated that with the addition of MBIS, a hysteresis loop forms in the positive-scan and negative-scan voltammetry. With the increment of MBIS concentration, the loop becomes larger, the onset of the inhibition breakdown moves to a more negative value, illustrating that the inhibition of MBIS is concentration dependent. This is in accordance with the reported result. The inhibition is also found to be convection dependent, with a similar behavior to concentration when the rotation speed of RDE increases. One interesting phenomenon in the voltammetry of MBIS-added solution is the transition between the breakdown of inhibition (active) and the rebuilt of inhibition (passive). The phenomenon only occurs when the MBIS concentration or the rotation speed of RDE is higher than a certain value. The phenomenon has not been observed with the presence PEI at a given concentration. If a minimal flux of inhibitor is required to maintain the inhibition blocking layer in the passive state, this transition from passive to active may imply a fast mass transfer of MBIS at higher concentration or higher intensity of convection. Additionally, it is found that at a given concentration the current efficiency of MBIS is much higher than PEI but with a similar surface coverage. The morphology of the healed crack reveals that the healing crystals grows in a controllable manner. The reduction of Ni on the sidewalls has been consistently inhibited, while the growth of healing crystals has been much less restricted from the crack tips. No defects were found along the interface between the substrate and the healing crystals which is believed to be the result of the much higher current efficiency. Although, annul-ring like defects still exist, the average distance between the annual-ring of MBIS is much larger that that of PEI, indicating a longer active growth period of healing crystals from crack tips. Further in-depth analysis is still underway to understand the phenomenon.

Nanoparticle and poly(methyl methacrylate) co-dispersion in anisole

Aqueous nanoparticle dispersions have been widely studied for their important industrial applications, including photocatalyst, coating, and casting. However, much less work has been conducted on nanoparticle dispersions in organic solvents, especially when co-dispersing with dissolved polymers. In this study, we explore TiO2/ZnO nanoparticle and poly(methyl methacrylate) (PMMA) co-dispersion in organic solvent anisole. To achieve uniformly dispersed suspensions, nanoparticle surface functionalization with nonanoic acid and 1-pentanol is conducted. Nonanoic acid has higher surface coverage on TiO2 and the two dispersants show similar surface coverage on ZnO. Heat treatment enhances the dispersant adsorption on the nanoparticle surfaces. For both TiO2/PMMA and ZnO/PMMA co-dispersions, higher solids loading leads to higher suspension viscosity. Higher volume fraction of nanoparticles in the nanoparticle plus PMMA solid phase results in lower viscosity, mainly by reducing the entanglement of the dissolved PMMA chains.

Influence of pore size of SBA-15 on activity and selectivity of H3[PMo12O40] supported on tailored SBA-15

Large pore SBA-15 was successfully synthesized and used as support material for molybdenum based oxidation catalysts. H3[PMo12O40] was supported on SBA-15 with modified pore radii (10, 14, 19 nm). All samples were prepared with a similar surface coverage of 1 Keggin ion per 13 nm2 independent of the pore radii. Structural evolution and catalytic activity of H3[PMo12O40] supported on SBA-15 (PMo12-SBA-15) with different pore radii (10, 14, 19 nm) were investigated under selective propene oxidation conditions by in situ X-ray absorption spectroscopy investigations. PMo12-SBA-15 (10, 14, 19 nm) formed a mixture of mostly tetrahedral [MoO4] and octahedral [MoO6] units during thermal treatment in propene oxidation conditions. A higher concentration of octahedral [MoO6] units and higher oligomerized [MoxOy] units were detected for act. PMo12-SBA-15 (10 nm) compared to act. PMo12-SBA-15 (14, 19 nm). The higher concentration of [MoxOy] units present in act. PMo12-SBA-15 (10 nm) resulted in an increased catalytic activity compared to activated PMo12-SBA-15 (14, 19 nm) with a lower concentration of [MoxOy] units. Selectivities towards oxidation products during propene oxidation were comparable and largely independent of the pore radii of act. PMo12-SBA-15 (10, 14, 19 nm). Apparently, tailoring the pore radius of silica SBA-15 permitted to prepare Mo oxide model systems to investigate correlation between activity and structure of characteristic oxide species at similar surface coverage.

Membrane protein resistance of oligo(ethylene oxide) self-assembled monolayers

As part of an effort to develop biointerfaces for structure-function studies of integral membrane proteins (IMPs) a series of oligo(ethylene oxide) self-assembled monolayers (OEO-SAMs) were evaluated for their resistance to protein adsorption (RPA) of IMPs on Au and Pt. Spectroscopic ellipsometry (SE) was used to determine SAM thicknesses and compare the RPA of HS(CH2)3O(CH2CH2O)6CH3 (1), HS(CH2)3O(CH2CH2O)6H (2), [HS(CH2)3]2CHO(CH2CH2O)6CH3 (3) and [HS(CH2)3]2CHO(CH2CH2O)6H (4), assembled from water. For both substrates, SAM thicknesses for 1 to 4 were found to be comparable indicating SAMs with similar surface coverages and OEO chain order and packing densities. Fibrinogen (Fb), a soluble plasma protein, and rhodopsin (Rd), an integral membrane G-protein coupled receptor, adsorbed to the SAMs of 1, as expected from previous reports, but not to the hydroxy-terminated SAMs of 2 and 4. The methoxy-terminated SAMs of 3 were resistant to Fb but, surprisingly, not to Rd. The stark difference between the adsorption of Rd to the SAMs of 3 and 4 clearly indicate that a hydroxy-terminus of the OEO chain is essential for high RPA of IMPs. The similar thicknesses and high RPA of the SAMs of 2 and 4 show the conditions of protein resistance (screening the underlying substrate, packing densities, SAM order, and conformational mobility of the OEO chains) defined from previous studies on Au are applicable to Pt. In addition, the SAMs of 4, exhibiting the highest resistance to Fb and Rd, were placed in contact with undiluted fetal bovine serum for 2h. Low protein adsorption (≈12.4ng/cm2), obtained under these more challenging conditions, denote a high potential of the SAMs of 4 for various applications requiring the suppression of non-specific protein adsorption.

Directing Cluster Formation of Au Nanoparticles from Colloidal Solution

Discrete clusters of closely spaced Au nanoparticles can be utilized in devices from photovoltaics to molecular sensors because of the formation of strong local electromagnetic field enhancements when illuminated near their plasmon resonance. In this study, scalable, chemical self-organization methods are shown to produce Au nanoparticle clusters with uniform nanometer interparticle spacing. The performance of two different methods, namely electrophoresis and diffusion, for driving the attachment of Au nanoparticles using a chemical cross-linker on chemically patterned domains of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) thin films are evaluated. Significantly, electrophoresis is found to produce similar surface coverage as diffusion in 1/6th of the processing time with an ~2-fold increase in the number of Au nanoparticles forming clusters. Furthermore, average interparticle spacing within Au nanoparticle clusters was found to decrease from 2-7 nm for diffusion deposition to approximately 1-2 nm for electrophoresis deposition, and the latter method exhibited better uniformity with most clusters appearing to have about 1 nm spacing between nanoparticles. The advantage of such fabrication capability is supported by calculations of local electric field enhancements using electromagnetic full-wave simulations from which we can estimate surface-enhanced Raman scattering (SERS) enhancements. In particular, full-wave results show that the maximum SERS enhancement, as estimated here as the fourth power of the local electric field, increases by a factor of 100 when the gap goes from 2 to 1 nm, reaching values as large as 10(10), strengthening the usage of electrophoresis versus diffusion for the development of molecular sensors.

Structural analysis of in situ biofilm formation on oral titanium implants

Background: The primary etiologic factor for peri-implant infections is the adhesion of biofilms on oral implant surfaces in the area of soft-tissue penetration. The aim of the present study was to examine in situ biofilm growth directly on implant-abutment surfaces without the use of oral splints and to determine the effect of intraoral abutment localization on biofilm growth. Materials and Methods: Fifteen titanium healing abutments were inserted in six patients for 14 days. The newly formed supragingival biofilm on the titanium surface of the healing abutments was stained with fluorescent Live/Dead Baclight kit before examination by confocal laser scanning microscopy. The biofilm was scanned in terms of its surface coverage and thickness and different sites. Results: The results show that the biofilm has a different structure in every patient, with the thickness of the biofilm structure ranging between 0 and 80 ΅m and the surface coverage between 0 and 97% of the abutment surface. There was similar biofilm surface coverage at different intraoral locations, whereas the biofilm was significantly thicker in the mandible as compared to maxillary implant abutments. Conclusion: The method uniquely describes an effective way to depict biofilm development on implant surfaces in the supra- and sub-gingival regions.

In-situ characterization of self-assembled monolayers of water-soluble oligo(ethylene oxide) compounds

In-situ spectroscopic ellipsometry (SE) was utilized to examine the formation of the self-assembled monolayers (SAMs) of the water-soluble oligo(ethylene oxide) [OEO] disulfide [S(CH 2CH 2O) 6CH 3] 2 {[S(EO) 6] 2} and two analogous thiols – HS(CH 2CH 2O) 6CH 3 {(EO) 6} and HS(CH 2) 3O(CH 2CH 2O) 5CH 3 {C 3(EO) 5} – on Au from aqueous solutions. Kinetic data for all compounds follow simple Langmuirian models with the disulfide reaching a self-limiting final state ( d = 1.2 nm) more rapidly than the full coverage final states of the thiol analogs ( d = 2.0 nm). The in-situ ellipsometric thicknesses of all compounds were found to be nearly identical to earlier ex-situ ellipsometric measurements suggesting similar surface coverages and structural models in air and under water. Exposure to bovine serum albumin (BSA) shows the self-limiting ( d = 1.2 nm) [S(EO) 6] 2 SAMs to be the most highly protein resistant surfaces relative to bare Au and completely-formed SAMs of the two analogous thiols and octadecanethiol (ODT). When challenged with up to near physiological levels of BSA (2.5 mg/mL), protein adsorption on the final state [S(EO) 6] 2 SAM was only 3% of that which adsorbed to the bare Au and ODT SAMs.