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The current challenge in tissue engineering is to design a platform that can provide appropriate topography and suitable surface chemistry to encourage desired cellular activities and to guide 3-D tissue regeneration. Compared with traditional cell culture materials, 3-D nanofibrous platforms offer a superior environment for promoting cell functions by mimicking the architecture of extracellular matrix (ECM). In this study, we present a technique to engineer freestanding 3-D titania nanofibrous structures on titanium substrates using femtosecond laser processing. The crystallinity, surface adhesion, and surface energy of the synthesized nanostructures are discussed. The effects of synthesized nanoarchitectures on the proliferation, morphology, and viability of MC3T3-E1 mouse osteoblast-like cells and NIH 3T3 mouse embryonic fibroblasts are investigated. The nanofibrous structures show high surface energy and hydrophilicity. The results from in vitro studies reveal that the titania nanofibrous architectures possess excellent biocompatibility and significantly enhances proliferation of both cell lines compared to untreated titanium specimens. Study of the cell morphology shows dynamic cell migration and attachment on the titania nanofibrous architecture. The bioactivity and biocompatibility of the engineered 3-D nanostructures suggest noticeable perspective for developing bio-functionalized scaffolds and implantable materials in regenerative medicine and clinical tissue engineering.

The purpose of this study was to evaluate the shear bond strength, the adhesive remnant index scores, and etch surface of teeth prepared for orthodontic bracket bonding with self-etching primer and Er:YAG laser conditioning. One hundred and twenty bovine incisors were randomly divided into four groups. In Group I (Control), the teeth were conditioned with 35% phosphoric acid for 15 seconds. In Group II the teeth were conditioned with Transbond Plus SEP (5 sec); III and IV were irradiated with the Er:YAG 150 mJ (11.0 J/cm²), 150 mJ (19.1 J/cm²), respectively, at 7-12 Hz with water spray. After surface preparation, upper central incisor stainless steel brackets were bonded with Transbond Plus Color Change Adhesive. The teeth were stored in water at 37°C for 24 hours and shear bond strengths were measured, and adhesive remnant index (ARI) was determined. The conditioned surface was observed under a scanning electron microscope. One-way ANOVA and chi-square test were used. Group I showed the significantly highest values of bond strength with a mean value of 8.2 megapascals (MPa). The lesser amount of adhesive remnant was found in Group III. The results of this study suggest that Er:YAG laser irradiation could not be an option for enamel conditioning.

A comprehensive investigation of anti-bacterial properties of graphene oxide (GO) and ultraviolet (UV) irradiated GO nanosheets was carried out. Microscopic characterization revealed that the GO nanosheet-like structures had wavy features and wrinkles or thin grooves. Fundamental surface chemical states of GO nanosheets (before and after UV irradiation) were investigated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Minimum inhibitory concentration (MIC) results revealed that UV irradiated GO nanosheets have more pronounced anti-bacterial behavior than GO nanosheets and standard antibiotic, kanamycin. The MIC of UV irradiated GO nanosheets was 0.125 μg ml⁻¹ for Escherichia coli and Salmonella typhimurium, 0.25 μg ml⁻¹ for Bacillus subtilis and 0.5 μg ml⁻¹ for Enterococcus faecalis, ensuring its potential as an anti-infective agent for controlling the growth of pathogenic bacteria. The minimum bactericidal concentration of normal GO nanosheets was determined to be two-fold higher than its corresponding MIC value, indicating promising bactericidal activity. The mechanism of anti-bacterial action was evaluated by measuring the enzymatic activity of β-D-galactosidase for the hydrolysis of o-nitrophenol-β-D-galactopyranoside.

The two-photon polymerization technique (2PP) uses non-linear absorption of femtosecond laser pulses to selectively polymerize photosensitive materials. 2PP has the ability to fabricate structures with a resolution from tens of micrometers down to hundreds of nanometers. Three-dimensional microstructuring by the 2PP technique provides many interesting possibilities for biomedical applications. This microstructuring technique is suitable with many biocompatible polymeric materials, such as polyethylene glycol, polylactic acid, polycaprolactone, gelatin, zirconium-based hybrids, and others. The process of fabrication does not require clean room conditions and does not use hazard chemicals or high temperatures. The most beneficial property of 2PP is that it is capable of producing especially complex three-dimensional (3-D) structures, including devices with overhangs, without using any supportive structure. The flexibility in controlling geometries and feature sizes and the possibility to fabricate structures without the addition of new material layers makes this technique particularly appealing for fabrication of 3-D scaffolds for tissue engineering.

The present study measured removal torque and bone-implant interface resistance of machined implants, acid-etched implants, or machined implants irradiated around the implant area with infrared low-level laser therapy (LLLT; 830 nm) immediately after surgery. There were statistically significant differences between Groups A (control) and B (rough surface) (P = .03). Implants with a rough surface seem to add resistance to the bone-implant interface compared with smooth titanium implants or implants treated with LLLT.

We investigated the production of free radicals on a poly(ether-ether-ketone) (PEEK) substrate under ultraviolet (UV) irradiation. The amount of the ketyl radicals produced from the benzophenone (BP) units in the PEEK molecular structure initially increased rapidly and then became almost constant. Our observations revealed that the BP units in PEEK acted as photoinitiators, and that it was possible to use them to control the graft polymerization of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). This "self-initiated surface graft polymerization" method is very convenient in the absence of external photoinitiator. We also investigated the effects of the monomer concentration and UV irradiation time on the extent of the grafted PMPC layer. Furthermore, as an application to improving the durability of artificial hips, we demonstrated the nanometer-scale photoinduced grafting of PMPC onto PEEK and carbon fiber-reinforced PEEK (CFR-PEEK) orthopedic bearing surfaces and interfaces. A variety of test revealed significant improvements in the water wettability, frictional properties, and wear resistance of the surfaces and interfaces., (© 2013 Published by Elsevier Ltd.)

An analytic model is developed to describe the inelastic processes occurring when keV Ne(+) ions are scattered at grazing incidence by the (100) surface of LiF. The large energy losses (up to 30 eV) of the reflected Ne(+) particles reported by Borisov et al (1999 Phys. Rev. Lett. 83 5378) are shown to arise specifically from the long-range coupling between the projectiles and the so-called Fuchs-Kliewer (FK) optical phonons of LiF whose fields extend far outside the surface. The strength of the coupling is estimated, allowing one to compute the average number of excited FK phonon quanta (ħωS = 0.071 eV) and hence the mean energy losses. For emerging, neutralized Ne(0), a distinct energy loss mechanism is shown to occur, namely the excitation of FK phonons and other types of surface collective modes associated with the screening of the F(0) 'hole' left behind by the neutralization process. This mechanism contributes a large fraction of the loss, additional to that suffered by the incident Ne(+) ion. The model explains the experimental observations quantitatively (1999 Phys. Rev. Lett. 83 5378). The paper ends with a discussion of the large energy broadening of the observed loss peaks.

In order to investigate the binding ability of Lactobacillus strains to Benzo(a)pyrene (BaP), 15 strains were analysed. L. plantarum CICC 22135 and L. pentosus CICC 23163 exhibited high efficiency in removing BaP from aqueous medium; the binding rates were 66.76% and 64.31%, respectively. This process was affected by temperature, incubation time and pH, and cell viability was not necessary for the binding ability. Additionally, both strains, especially strain CICC 23163 showed high specificity in binding BaP. The cell-BaP complexes were stable in aqueous medium. The mechanism of binding was investigated by examining the binding ability of different components of the microorganism cells. The results revealed that peptidoglycans played an important role in binding BaP and its structural integrity was required. Consequently, we proposed that the mechanism of this process was a physisorption and peptidoglycan was the main binding site. These two strains may be used for dietary detoxification in human diet and animal feed., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Surface microstructure and chemical composition of the implant are very important for its osseointegration in vivo. In this paper, a hierarchical micropattern covered with calcium phosphate (Ca/P phase) was obtained on titanium (Ti) implant surface by femtosecond lasers (FSL) irradiation in hydroxyapatite suspension. The hierachical micropattern as well as Ca/P phase increased osteoblastic cell adhesion. Higher expression of osteogenic markers (osteocalcin, osteopontin, and runt related transcription factor-2) on the surface treated by FSL of 2.55 J/cm(2) indicated the favorable effect of laser treatment on cell differentiation. In vivo studies were carried out to evaluate the effect of laser treatment and Ca/P deposition on the osseointegration. It showed that the binding capacity between bone and FSL-treated Ti implants was obviously stronger than that between bone and polished or sand blasting and acid etching (SLA) Ti implants. Bone trabecula surrounded the FSL-treated implants without fibrous tissue after 8-week implantation. Also, higher bone mineral density was seen surrounding the FSL-treated implants. Our in vitro and in vivo studies demonstrated that the FSL induced micropattern and Ca/P phase had positive effects on the acceleration of early osseointegration of Ti implants with bone tissue.

Cell-material surface interaction plays a critical role in osseointegration of prosthetic implants used in orthopedic surgeries and dentistry. Different technical approaches exist to improve surface properties of such implants either by coating or by modification of their topography. Femtosecond laser treatment was used in this study to generate microspotted lines separated by 75, 125, or 175μm wide nanostructured interlines on stainless steel (316L) plates. The hydrophobicity and carbon content of the metallic surface were improved simultaneously through this method. In vitro testing of the laser treated plates revealed a significant improvement in adhesion of human endothelial cells and human bone marrow mesenchymal stem cells (hBM MSCs), the cells involved in microvessel and bone formation, respectively, and a significant decrease in fibroblast adhesion, which is implicated in osteolysis and aseptic loosening of prostheses. The hBM MSCs showed an increased bone formation rate on the laser treated plates under osteogenic conditions; the highest mineral deposition was obtained on the surface with 125μm interline distance (292±18mg/cm(2) vs. 228±43mg/cm(2) on untreated surface). Further in vivo testing of these laser treated surfaces in the native prosthetic implant niche would give a real insight into their effectiveness in improving osseointegration and their potential use in clinical applications., (Copyright © 2013 Elsevier B.V. All rights reserved.)

We present a model for a Yb-doped distributed Bragg reflector (DBR) waveguide laser fabricated in phosphate glass using the femtosecond laser direct-write technique. The model gives emphasis to transverse integrals to investigate the energy distribution in a homogenously doped glass, which is an important feature of femtosecond laser inscribed waveguide lasers (WGLs). The model was validated with experiments comparing a DBR WGL and a fiber laser, and then used to study the influence of distributed rare earth dopants on the performance of such lasers. Approximately 15% of the pump power was absorbed by the doped "cladding" in the femtosecond laser inscribed Yb doped WGL case with the length of 9.8 mm. Finally, we used the model to determine the parameters that optimize the laser output such as the waveguide length, output coupler reflectivity and refractive index contrast.

The photoinduced formation of silver nanoprisms from smaller silver seed particles in the presence of citrate anions is a classic example of a photomorphic reaction. In this case, light is used as a convenient tool to dynamically manipulate the shape of metal nanoparticles. To date, very little is known about the prevailing reaction mechanism of this type of photoreaction. Here we provide a detailed study of the shape transformation dynamics as a function of a range of different process parameters, such as photon energy and photon flux. For the first time, we provide direct evidence that the photochemical synthesis of silver nanoprisms from spherical seed nanoparticles proceeds via a light-activated two-dimensional coalescence mechanism. On the other hand, we could show that Ostwald ripening becomes the dominant reaction mechanism when larger silver nanoprisms are grown from photochemically synthesized smaller nanoprisms. This two-step reaction proceeds significantly faster and yields more uniform, sharper nanoprisms than the classical one-step photodevelopment process from seeds. The ability to dynamically control nanoparticle shapes and properties with light opens up novel synthesis avenues but also, more importantly, allows one to conceive new applications that exploit the nonstatic character of these nanoparticles and the ability to control and adjust their properties at will in a highly dynamic fashion.

When exposed to corrosive anodic electrochemical environments, Pt alloy nanoparticles (NPs) undergo selective dissolution of the less noble component, resulting in catalytically active bimetallic Pt-rich core-shell structures. Structural evolution of PtNi6 and PtNi3 NP catalysts during their electrochemical activation and catalysis was studied by in situ anomalous small-angle X-ray scattering to obtain insight in element-specific particle size evolution and time-resolved insight in the intraparticle structure evolution. Ex situ high-energy X-ray diffraction coupled with pair distribution function analysis was employed to obtain detailed information on the atomic-scale ordering, particle phases, structural coherence lengths, and particle segregation. Our studies reveal a spontaneous electrochemically induced formation of PtNi particles of ordered Au3Cu-type alloy structures from disordered alloy phases (solid solutions) concomitant with surface Ni dissolution, which is coupled to spontaneous residual Ni metal segregation during the activation of PtNi6. Pt-enriched core-shell structures were not formed using the studied Ni-rich nanoparticle precursors. In contrast, disordered PtNi3 alloy nanoparticles lose Ni more rapidly, forming Pt-enriched core-shell structures with superior catalytic activity. Our X-ray scattering results are confirmed by STEM/EELS results on similar nanoparticles.

We introduce the use of ferromagnetic resonance (FMR) to actuate mechanical resonances in as grown arrays of carbon nanotubes (CNTs) loaded with Ni particles (Ni-CNTs). This contactless method is closely related to the magnetic resonance force microscopy technique and provides spatial selectivity of actuation along the array. The Ni-CNT arrays are grown by chemical vapor deposition and are composed of homogeneous CNTs with uniform length (~600 nm) and almost equal diameter (~20 nm), which are loaded with Ni catalyst particles at their tips due to the tip growth mode. The vibrations of the Ni-CNTs are actuated by relying on the driving force that appears due to the FMR excited at about 2 GHz in the Ni particles (diameter ~100 nm). The Ni-CNT oscillations (frequency ~40 MHz) are detected mechanically by atomic force microscopy. The acquired oscillation images of the Ni-CNT uniform array reveal clear maxima in the spatial distribution of the oscillation amplitudes. We attribute these maxima to the "sensitive slices", i.e., the spatial regions of the Ni-CNT array where the FMR condition is met. Similar to magnetic resonance imaging, the sensitive slice is determined by the magnetic field gradient and moves along the Ni-CNT array as the applied magnetic field is ramped. Our excitation method does not require the presence of any additional microfabricated electrodes or coils near the CNTs and is particularly advantageous in cases where the traditional electrical actuation methods are not effective or cannot be implemented. The remote actuation can be effectively implemented also for arrays of other magnetic nanomechanical resonators.

The conduction properties of graphene were tuned by tailoring the lattice by using an accelerated helium ion beam to embed low-density defects in the lattice. The density of the embedded defects was estimated to be 2-3 orders of magnitude lower than that of carbon atoms, and they functionalized a graphene sheet in a more stable manner than chemical surface modifications can do. Current modulation through back gate biasing was demonstrated at room temperature with a current on-off ratio of 2 orders of magnitude, and the activation energy of the thermally activated transport regime was evaluated. The exponential dependence of the current on the length of the functionalized region in graphene suggested that conduction tuning is possible through strong localization of carriers at sites induced by a sparsely distributed random potential modulation.

With its electrical carrier type as well as carrier densities highly sensitive to light, graphene is potentially an ideal candidate for many optoelectronic applications. Beyond the direct light-graphene interactions, indirect effects arising from induced charge traps underneath the photoactive graphene arising from light-substrate interactions must be better understood and harnessed. Here, we study the local doping effect in graphene using focused-laser irradiation, which governs the trapping and ejecting behavior of the charge trap sites in the gate oxide. The local doping effect in graphene is manifested by large Dirac voltage shifts and/or double Dirac peaks from the electrical measurements and a strong photocurrent response due to the formation of a p-n-p junction in gate-dependent scanning photocurrent microscopy. The technique of focused-laser irradiation on a graphene device suggests a new method to control the charge-carrier type and carrier concentration in graphene in a nonintrusive manner as well as elucidate strong light-substrate interactions in the ultimate performance of graphene devices.

Possibility to form three-dimensional (3D) micro-structures in silicone elastomer (polydimethylsiloxane; PDMS) doped with different photo-initiators was systematically investigated using direct laser writing with femtosecond laser pulses at different exposure conditions. Accuracy of the 3D structuring with resolution of ~5 μm and a fabrication throughput of ~720 μm(3)/s, which is exceeding the previously reported values by ~ 300(×), was achieved. Practical recording velocities of ~ 1 mm/s were used in PDMS with isopropyl-9H-thioxanthen-9-one (ISO) and thioxanthen-9-one (THIO) photo-initiators which both have absorption at around 360 nm wavelength. The 3D laser fabrication in PDMS without any photo-initiator resulting in a fully bio-compatible material has been achieved for the first time. Rates of multi-photon absorption and avalanche for the structuring of silicone are revealed: the two-photon absorption is seeding the avalanche of a radical generation for subsequent cross-linking. Direct writing enables a maskless manufacturing of molds for soft-lithography and 3D components for microfluidics as well as scaffolds for grafts in biomedical applications.

We study numerically depressed-index cladding, buried, micro-structured optical waveguides that can be formed in a lithium niobate crystal by femtosecond laser writing. We demonstrate to which extent the waveguiding properties can be controlled by the waveguide geometry at the relatively moderate induced refractive index contrasts that are typical of the direct femtosecond inscription.

We demonstrated a new method to fabricate micron-sized grooves with high aspect ratios in silicon wafers by combining femtosecond laser irradiation and oxygen-dependent acid etching. Femtosecond laser was employed to induce structure changes and incorporate oxygen into silicon, and then materials in oxygen-containing regions were etched by hydrofluoric acid (HF) solution to form grooves. The etching could be attributed to the reaction between HF and silicon oxides formed by femtosecond laser irradiation. The dependences of the aspect ratios of grooves on the laser fluence and the scanning velocity were also investigated.

Multi-pulse laser induced damage threshold (LIDT) for metallic mirrors are important issue for laser diagnostics in future fusion devices. In this paper, the mechanism of multi-pulse LIDT and the influence of the slip formation and oxidization in atmosphere were investigated experimentally with a Nd:YAG pulse laser whose pulse width and wavelength are ~ 5 ns and 1064 nm, respectively. From detailed surface analysis of laser irradiated part by transmission electron microscopy (TEM), it was found that the miniaturization of crystal size and slip formation were observed on damaged area. Oxidization feature was also revealed from the TEM analysis. It was shown that the multi-pulse LIDT could be increased under vacuum condition compared with that in air atmosphere.

UV laser induced damage (LID) on exit surface of fused silica could cause modulation effect to transmitted beam and further influence downstream propagation properties. This paper presents our experimental and analytical studies on this topic. In experiment, a series of measurement instruments are applied, including beam profiler, interferometer, microscope, and optical coherent tomography (OCT). Creating and characterizing of LID on fused silica sample have been implemented. Morphological features are studied based on their particular modulation effects on transmitted beam. In theoretical investigation, analytical modeling and numerical simulation are performed. Modulation effects from amplitude, phase, and size factors are analyzed respectively. Furthermore, we have novelly designed a simplified polygon model to simulate actual damage site with multiform modulation features, and the simulation results demonstrate that the modeling is usable and representative.

Molecules with donor (diphenylamine) and acceptor moieties (dicyano or cyanoacrylic acid moieties) were linked by fluorene or spirobisfluorene cores and the chain length has been changed by introducing a thiophene group between fluorene and diphenylamine. Four different kinds of fluorene and spirobisfluorene compounds were adsorbed from highly diluted solutions at ultra-thin nanoporous TiO2 (np-TiO2), Au and ITO surfaces. Charge separation has been investigated by surface photovoltage spectroscopy in the fixed capacitor and Kelvin probe arrangements in vacuum. Striking differences between the interaction of linking (dicyano or cyanoacrylic moieties) and different substrates were observed. Intra-molecular charge separation and electron injection have been distinguished and the directed adsorption of spiro compounds was deduced.

Objective: To investigate the influence of the reprocessing technique of enzymatic bath with ultrasonic cleaning and ethylene oxide sterilization on the chemical properties and morphological structure of polymeric coatings of guide wire for regular guiding catheter., Methods: These techniques simulated the routine of guide wire reprocessing in many hemodynamic services in Brazil and other countries. Samples from three different manufacturers were verified by scanning electron microscopy and X-ray photoelectron spectroscopy., Results: A single or double sterilization of the catheters with ethylene oxide was not associated with morphological or chemical changes. However, scanning electron microscopy images showed that the washing method was associated with rough morphological changes, including superficial holes and bubbles, in addition to chemical changes of external atomic layers of polymeric coating surfaces, as detected by the X-ray photoelectron spectroscopy method, which is compatible with extended chemical changes on catheter surfaces., Conclusion: The reprocessing of the catheters with ethylene oxide was not associated with morphological or chemical changes, and it seemed appropriate to maintain guide wire coating integrity. However, the method combining chemical cleaning with mechanical vibration resulted in rough anatomical and chemical surface deterioration, suggesting that this reprocessing method should be discouraged.

The stabilizing encapsulation of a microbubble-based ultrasound contrast agent (UCA) critically affects its acoustic properties. Polymers, which behave differently from materials commonly used (i.e., lipids or proteins) for monolayer encapsulation, have the potential for better stability and improved control of encapsulation properties. Air-filled microbubbles coated with poly(DL-lactic acid) (PLA) are characterized here using in vitro acoustic experiments and several models of encapsulation. The interfacial rheological properties of the encapsulation are determined according to each model using attenuation of ultrasound through a suspension of microbubbles. Then the model predictions are compared with scattered non-linear (sub- and second harmonic) responses. For this microbubble population (average diameter, 1.9 μm), the peak in attenuation measurement indicates a weighted-average resonance frequency of 2.5-3 MHz, which, in contrast to other encapsulated microbubbles, is lower than the resonance frequency of a free bubble of similar size (diameter, 1.9 μm). This apparently contradictory result stems from the extremely low surface dilational elasticity (around 0.01-0.07 N/m) and the reduced surface tension of the poly(DL-lactic acid) encapsulation, as well as the polydispersity of the bubble population. All models considered here are shown to behave similarly even in the non-linear regime because of the low surface dilational elasticity value. Pressure-dependent scattering measurements at two different excitation frequencies (2.25 and 3 MHz) revealed strongly non-linear behavior with 25-30 dB and 5-20 dB enhancements in fundamental and second-harmonic responses, respectively, for a contrast agent concentration of 1.33 μg/mL in the suspension. Sub-harmonic responses are registered above a relatively low generation threshold of 100-150 kPa, with up to 20 dB enhancement beyond that pressure. Numerical predictions from all models show good agreement with the experimentally measured fundamental response, but not with the experimental second-harmonic response. The characteristic features of sub-harmonic responses and the steady response beyond the threshold are matched well by model predictions. However, prediction of the threshold value depends on estimated properties and size distribution. The variation in size distribution from sample to sample leads to variation in estimates of encapsulation properties: the lowest estimated value for surface dilational viscosity better predicts the sub-harmonic threshold., (Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

Laser direct write techniques represent a prospective alternative for engineering a new generation of hybrid biomaterials via the creation of patterns consisting of biological proteins onto practically any type of substrate. In this paper we report on the characterization of fibronectin features obtained onto titanium substrates by UV nanosecond laser transfer. Fourier-transform infrared spectroscopy measurements evidenced no modification in the secondary structure of the post-transferred protein. The molecular weight of the transferred protein was identical to the initial fibronectin, no fragment bands being found in the transferred protein's Western blot migration profile. The presence of the cell-binding domain sequence and the mannose groups within the transferred molecules was revealed by anti-fibronectin monoclonal antibody immunolabelling and FITC-Concanavalin-A staining, respectively. The in vitro tests performed with MC3T3-E1 osteoblast-like cells and Swiss-3T3 fibroblasts showed that the cells' morphology and spreading were strongly influenced by the presence of the fibronectin spots.

The nano-precursors in the subsurface of Nd:YLF crystal were limiting factor that decreased the laser-induced damage threshold (LIDT) of HfO(2)/SiO(2) high reflection (HR) coatings irradiated from crystal-film interface. To investigate the contribution of electric-field (E-field) to laser damage originating from nano-precursors and then to probe the distribution of vulnerable nano-precursors in the direction of subsurface depth, two 1064 nm HfO(2)/SiO(2) HR coatings having different standing-wave (SW) E-field distributions in subsurface of Nd:YLF c5424181043036123rystal were designed and prepared. Artificial gold nano-particles were implanted into the crystal-film interface prior to deposition of HR coatings to study the damage behaviors in a more reliable way. The damage test results revealed that the SW E-field rather than the travelling-wave (TW) E-field contributed to laser damage. By comparing the SW E-field distributions and LIDTs of two HR coating designs, the most vulnerable nano-precursors were determined to be concentrated in a thin redeposition layer that is within 100 nm from the crystal-film interface.

Environmentally friendly and cyanide-free sulfate bath under continuous current and the corrosion behavior of electrodeposits of zinc-iron alloys were studied by means of electrochemical tests in a solution of 3.5% NaCl in presence and absence of glycine. The effects of pH on the quality of Zn-Fe coatings were investigated in order to improve uniformity and corrosion protection performance of the coating films. The deposit morphology was analyzed using scanning electron microscopy (SEM), and X-ray diffraction (XRD) was used to determine the preferred crystallographic orientations of the deposits. It was found that the uniformity and corrosion resistance of Zn-Fe coating films were strongly associated with pH of the coating electrolyte. To obtain the effect of pH on the film quality and corrosion performances of the films, the corrosion test was performed with potentiodynamic anodic polarization method. It was also observed that uniformity and corrosion resistivity of the coating films were decreased towards pH = 5 and then improved with increasing pH value of the electrolyte. The presence of glycine in the plating bath decreases the corrosion resistance of Zn-Fe coatings.

The formation mechanism of space charges in polyimide (PI) which was exposed to dielectric barrier discharge (DBD) in SF6 medium and the effects of the space charges on interfacial and electrical properties of PI were investigated. The variation of normalized surface charge density on PI sample was calculated and illustrated for different DBD exposure times. The surface potential was measured to determine the effect of the space charges on the sample. Then, the contact angle values were measured to obtain the relation between the surface energy and the surface charge density. The expressions for the total charge and the concentration of trapped electrons were derived by using Poisson and continuity equations at stationary state. The space charges were determined experimentally by using thermally stimulated depolarization current (TSDC) method. Also, SEM image and FTIR spectrum of virgin and treated samples were presented to observe the structural variations. It was seen that the approach for the formation mechanism of the space charges agreed with the experimental data. However, it was concluded particularly for the short-time DBD treatments that the space charges accumulated in the sample should be considered besides the effects of surface functionalization in the determination of the surface energy.

The relationship between the profile of the structures obtained by multiphoton polymerization and the optical parameters of nanofabrication systems has been studied theoretically for a multipulse scheme. We find that the profile of sub-wavelength structures is greatly affected by the evanescent waves affect. Not only is the photocured polymer voxel affected by the beam profile, but the beam propagation behavior is influenced by the photocured polymer voxel. This gives us a new view of matter-light interactions in multipulse polymerization process, which is useful to the accurate control of the nanofabrication profile and the selection of new nanofabrication materials.

Purpose: Weekly disposable soft contact lenses have been widely used recently, but their shield effects against ultraviolet (UV) irradiation remain to be evaluated. This study investigated the bioprotective effects of several weekly soft contact lenses against UVB irradiation on the corneal surface in a mouse model., Methods: Fifty ICR mice were randomly divided into five groups: (1) blank control, (2) exposed to UVB without contact lens protection, (3) exposed to UVB and protected with Vifilcon A contact lenses, (4) exposed to UVB and protected with Etafilcon A contact lenses, and (5) exposed to UVB and protected with HEMA+MA contact lenses. The exposure to UVB irradiation was performed at 0.72 J/cm²)/day after anesthesia for a 7-day period, followed by cornea surface assessment for smoothness, opacity, and grading of lissamine green staining. Tissue sections were prepared for hematoxylin and eosin staining and immunohistochemical detection by using antibodies against myeloperoxidase, cytokeratin-5, P63, Ki-67, nuclear factor-kappa B (p65), cyclooxygenase-2, Fas L, and Fas., Results: The results showed impaired corneal surface with myeloperoxidase+ polymorphonuclear leukocyte infiltration into the stroma after UVB exposure, in contrast to the intact status of the blank controls. The corneas with Etafilcon A and HEMA+MA contact lenses maintained more cells positive for cytokeratin-5, P63, and Ki-67 compared to those with Vifilcon A or without contact lens protection. Furthermore, less proinflammatory factors, including nuclear factor-kappa (p65), cyclooxygenase-2, Fas L, and Fas, were induced in the corneas protected by Etafilcon A and HEMA+MA., Conclusions: This study demonstrated various protective effects of weekly disposable contact lenses against UVB irradiation. The mouse model used in the present study may be used extensively for in vivo assessment of UV shield efficacy.

A sub-monolayer distribution of isolated molecular Fe14 (bta)6 nanomagnets is deposited intact on a Au(111) surface and investigated by X-ray magnetic circular dichroism spectroscopy. The entropy variation with respect to the applied magnetic field is extracted from the magnetization curves and evidences high magnetocaloric values at the single molecule level., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We show that surface swelling is the first step in the interaction of a single femtosecond laser pulse with PMMA. This is followed by perforation of the swollen structure and material ejection. The size of the swelling and the perforated hole increases with pulse energy. After certain energy the swelling disappears and the interaction is dominated by the ablated hole. This behaviour is independent of laser polarization. The threshold energy at which the hole size coincides with size of swelling is 1.5 times that of the threshold for surface swelling. 2D molecular dynamics simulations show surface swelling at low pulse energies along with void formation below the surface within the interaction region. Simulations show that at higher energies, the voids coalesce and grow, and the interaction is dominated by material ejection.

A surface micro/nano structuring technique was demonstrated by utilizing a picosecond laser beam to rapidly modify the optical property of copper surfaces with a scanning speed up to tens of millimeters per second. Three kinds of surface micro/nanostructures corresponding to three levels of reflectance were produced which are obviously different from those induced by a femtosecond or nanosecond laser. Specifically, a porous coral-like structure results in over 97% absorptivity in the visible spectral region and over 90% absorptivity in average in the UV, visible, and NIR regions (250 - 2500 nm). Potential applications may include solar energy absorbers, thermal radiation sources, and radiative heat transfer devices.

Many kinds of subsurface defects are always present together in the subsurface of fused silica optics. It is imperfect that only one kind of defects is isolated to investigate its impact on laser damage. Therefore it is necessary to investigate the impact of subsurface defects on laser induced damage of fused silica optics with a comprehensive vision. In this work, we choose the fused silica samples manufactured by different vendors to characterize subsurface defects and measure laser induced damage. Contamination defects, subsurface damage (SSD), optical-thermal absorption and hardness of fused silica surface are characterized with time-of-flight secondary ion mass spectrometry (TOF-SIMS), fluorescence microscopy, photo-thermal common-path interferometer and fully automatic micro-hardness tester respectively. Laser induced damage threshold and damage density are measured by 351 nm nanosecond pulse laser. The correlations existing between defects and laser induced damage are analyzed. The results show that Cerium element and SSD both have a good correlation with laser-induced damage thresholds and damage density. Research results evaluate process technology of fused silica optics in China at present. Furthermore, the results can provide technique support for improving laser induced damage performance of fused silica.

We demonstrate the fine tuning capability of femtosecond laser surface modification as a permanent trimming mechanism for silicon photonic components. Silicon microring resonators with a 15 µm radius were irradiated with single 400 nm wavelength laser pulses at varying fluences. Below the laser ablation threshold, surface amorphization of the crystalline silicon waveguides yielded a tuning rate of 20 ± 2 nm/J · cm(-2)with a minimum resonance wavelength shift of 0.10nm. Above that threshold, ablation yielded a minimum resonance shift of -1.7 nm. There was some increase in waveguide loss for both trimming mechanisms. We also demonstrated the application of the method by using it to permanently correct the resonance mismatch of a second-order microring filter.

This paper studies the variations in morphology of SnO2 nanostructures thin films deposited by using e-beam technique with the substrate temperature, oxygen partial pressure and the film thickness. The e-beam conditions were optimized to get crystalline nanosheets of SnO2. The films of 100-700 nm thickness were deposited on quartz substrates at temperatures ranging from room temperature (RT) to 300 degrees C and oxygen partial pressure ranging from 0 to 200 sccm. The nanostructured films have been characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and Energy dispersive spectroscopy (EDS) measurements. XRD results show that the films deposited at RT and 100 degrees C were amorphous, however, for 200 degrees C and 300 degrees C, the films showed crystalline nature with rutile structure. Also, the crystallinity increased with the increase of oxygen partial pressure. FE-SEM images revealed that at RT and 100 degrees C of substrate temperature, the film consist of spherical particles, whereas, the films deposited at 200 degrees C and 300 degrees C consist of sheet like morphology having thickness -40 nm and lateral dimension of 1 microm, respectively. The size of the nanosheets increased with the increase of substrate temperature and oxygen partial pressure due to the enhancement in the crystallinity of the films. A possible growth mechanism of the formation of SnO2 nanosheets is discussed.

Objective: To evaluate and compare the root surface morphological changes after 980-nm diode laser-aided circumferential supracrestal fiberotomy (CSF) on fluorosed and non-fluorosed teeth., Materials and Methods: The sample comprised 27 orthodontic patients (14 males and 13 females; mean age  =  17.3 years) with and without fluorosis, from whom 40 fluorosed and 40 non-fluorosed premolar teeth were extracted for orthodontic reasons. Conventional (control group) and laser-aided (experimental group) CSF was performed on fluorosed and non-fluorosed teeth indicated for orthodontic extraction, using a scalpel and a 980-nm diode laser at 2.5 W power, respectively. Subsequently, teeth were extracted, sectioned, and examined by scanning electron microscope to assess the ultrastructural changes., Results: There were differences in surface morphology among fluorosed and non-fluorosed roots in the control group. The root specimens of both fluorosed and non-fluorosed teeth irradiated by diode laser exhibited no evidence of smear layer, laser-induced pitting or cavitation, linear cuts/markings, carbonization of surface, and heat-induced surface cracking. However, a glazed or slightly melted appearance was observed in root specimens of fluorosed teeth after diode laser irradiation., Conclusions: These findings suggest that the diode laser-aided CSF procedure is free from thermal hazard on non-fluorosed root surfaces but may provoke some thermal changes on fluorosed root surfaces.

Large-area nanopatterning technology has demonstrated high potential which can significantly enhance the performance of a variety of devices and products such as LEDs, solar cells, hard disk drives, laser diodes, wafer-level optics, etc. But various existing patterning technologies cannot well meet industrial-level application requirements in term of high resolution, high throughput, low cost, large patterned areas, and the ability to pattern on non-ideal surfaces or waters. Soft UV-nanoimprint lithography (UV-NIL) by using a flexible mold has been proven to be a cost-effective mass production method for patterning large-area structures up to wafer-level (300 mm) in the micrometer and nanometer scale, fabricating complex 3-D micro/nano structures, especially making large-area patterns on the non-planar surfaces even curved substrates at low-cost and with high throughput. In particular, it provides an ideal solution and a powerful tool for mass producing micro/nanostructures over large areas at low cost for the applications in compound semiconductor optoelectronics and nanophotonic devices, especially for LED patterning. That opens the way for many applications not previously conceptualized or economically feasible. The flexible mold is the most critical elements for soft UV-NIL. The performance of the flexible mold has a decisive effect on the soft UV-NIL in term of resolution, patterning area, throughput, uniformity of the imprinted patterns, and repeatability of multi-imprinting. The key enabler that can fulfill mass production of micro-and nanostructures over large areas by NIL is the continual advancement of mold techniques (structures, materials and fabrication processes) towards higher resolution over a larger area at a lower cost. This paper provides a comprehensive review on the structural types, materials used and fabrication methods of various flexible molds in soft UV-NIL, surveys major progress in various flexible molds, particularly highlights some concluding remarks and generalizations. Two key issues for flexible molds, deformation mechanism and controlling solution of soft molds as well as fabrication of large area (wafer level) master template, are described in detail. Furthermore, prospects, challenges and future directions for flexible molds are addressed. Finally, some potential or promising solutions for improving the performance of flexible molds and soft UV-NIL process, as well as some important conclusions are presented.

Property degradation of the medical grade polymers after gamma irradiation is the primary concern that limits longevity of them. Though the conventional antioxidant material helps to reduce the degradation but it limits the degree of crosslinking of the polymer. The objective of the present work is to study the influence of multi walled carbon nanotubes (MWCNTs) on restricting the degradation of mechanical properties of medical grade ultra high molecular weight polyethylene (UHMWPE) after its irradiation. UHMWPE was reinforced by chemically treated MWCNTs at different concentrations such as 0.5, 1.0, 1.5, and 2.0 wt%. The test samples were then subjected to Co⁶⁰ gamma irradiation with an integral dose of 25, 50, 75 and 100 kGy in air. The mechanical properties of irradiated samples were evaluated within 10 days, 60 and 120 days after irradiation. It was observed that the mechanical properties of virgin UHMWPE and nanocomposites were enhanced immediately after irradiation but they were found to be reduced at later stages. It was also observed that the presence of MWCNTs limited the ageing degradation of the mechanical properties of UHMWPE. Raman spectroscopic and TEM studies confirmed the formation of irradiation induced defects on the MWCNTs. Electron spin resonance studies showed that the relative radical intensity of virgin UHWMPE was reduced significantly with an increase of MWCNTs concentration confirming the radical scavenging ability of them. It is concluded that MWCNTs restricted the ageing degradation of irradiated UHMWPE., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objectives: The aim of this study was to compare the effects of three different surface treatments in enhancing porcelain zirconia bonding., Methods: Totally, 160 densely sintered zirconia specimens were prepared and randomly divided into four study groups: control (no treatment, Group C), sandblasting (Group S), sandblasting followed by regeneration firing (Group SH), and laser irradiation (pulse mode) on a CO₂ laser system (Group L). After surface treatment, porcelain powders were veneered on zirconia surface. Half of the specimens in each group were evaluated without aging (initial shear bond strength - initial SBS), and the other half was tested after being stored in water for one month (aging SBS). X-ray diffractometry (XRD) was used to observe any crystallographic transformation at zirconia surface. Results were statistically analyzed using analysis of variance (ANOVA) and Turkey test (=0.05)., Results: The initial average SBS values of Group S, Group SH, and Group L were 31.3 ± 5.7 MPa, 29.2 ± 7.0 MPa and 32.1 ± 7.5 MPa, respectively. The differences among these three groups were not significant. The control group had significantly lower value, 24.8 ± 6.7 MPa, than those of Group S and Group L. Furthermore, there was no significant difference between initial and aging values in each group. XRD analysis showed that sandblasting caused tetragonal to monoclinic phase transformation. Regeneration firing reversed such a transformation. However, crystallographic transformation could not be detected in laser treated specimens., Significance: Both sandblasting and laser irradiation increased porcelain zirconia bond strength. The presented new modified laser pre-treatment might be an alternative way to sandblasting for improving zirconia/porcelain integration., (Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

This study evaluated the effects of the photoactivation source and restorative material on the development of caries-like lesions on human enamel after an in vitro pH challenge. Enamel cavities were prepared in 36 blocks, which were assigned to two groups according to the restorative material: resin-modified glass ionomer (RMGI) and composite resin (CR). Samples were exposed to quartz-tungsten-halogen lamp, argon-ion laser, or light-emitting diode (n = 6). The Knoop microhardness (KHN) values of the top surface of all materials were evaluated. Restored enamel blocks were thermocycled and subjected to 10 demineralization-remineralization cycles at 37°C. KHN analysis of the superficial enamel was performed by four indentations located 100 μm from the restoration margin. The material KHN was not affected by the photoactivation source. No significant difference in KHN was noted between CR and RMGI. The enamel surface around RMGI exhibited a higher KHN (272.8 KHN) than the enamel around CR (93.3 KHN), regardless of the photoactivation source. Enamel demineralization around the dental restoration was not influenced by the photoactivation source. Less enamel demineralization was observed around the RMGI than around the CR restoration.

Patterning of nanowires in a controllable, tunable manner is important for the fabrication of functional nanodevices. Here we present a simple approach for tunable nanowire patterning using standing surface acoustic waves (SSAW). This technique allows for the construction of large-scale nanowire arrays with well-controlled patterning geometry and spacing within 5 s. In this approach, SSAWs were generated by interdigital transducers, which induced a periodic alternating current (ac) electric field on the piezoelectric substrate and consequently patterned metallic nanowires in suspension. The patterns could be deposited onto the substrate after the liquid evaporated. By controlling the distribution of the SSAW field, metallic nanowires were assembled into different patterns including parallel and perpendicular arrays. The spacing of the nanowire arrays could be tuned by controlling the frequency of the surface acoustic waves. Additionally, we observed 3D spark-shaped nanowire patterns in the SSAW field. The SSAW-based nanowire-patterning technique presented here possesses several advantages over alternative patterning approaches, including high versatility, tunability, and efficiency, making it promising for device applications.

We demonstrate, for the first time, time- and cost-effective replication of sub-micrometer features from a soft PDMS mold onto a bulk chalcogenide glass over a large surface area. A periodic array of sub-micrometer lines (diffraction grating) with period 625 nm, amplitude 45 nm and surface roughness 3 nm was imprinted onto the surface of the chalcogenide AsSe(2) bulk glass at temperature 225°C, i.e. 5°C below the softening point of the glass. Sub-micrometer soft lithography into chalcogenide bulk glasses shows good reliability, reproducibility and promise for feasible fabrication of various dispersive optical elements, anti-reflection surfaces, 2D photonic structures and nano-structured surfaces for enhanced photonic properties and chemical sensing.

We describe the fabrication of nanostructures on SiGe film by KrF excimer laser with nanosecond pulse width, and find a more direct and clear relationship between the laser irradiation conditions and the nanoscale structures. Perfect annular nanostructures around scattering points on the SiGe film are firstly obtained after the irradiation of a KrF excimer pulse laser beam (100 mJ/cm(2)) at different incident angles. The different shapes of annular structures are related to different energy distributions due to the optical interference between the scattered light and the incident beam. As laser energy increases, a threshold of pulse energy (230 mJ/cm(2)) is found, above which a droplet-like morphology completely replacing the surface annular structures. And the disorder morphology is mainly caused by the thermal effect of the incident beam.

A method for precise multi-spot parallel ultrafast laser material structuring is presented based on multi-beam interference generated by dynamic spatial phase engineering. A Spatial Light Modulator (SLM) and digitally programming of phase masks are used to accomplish the function of a multi-facet pyramid lens, so that the laser beam can be spatially modulated to create beam multiplexing and desired two-dimensional (2D) multi-beam interference patterns. Various periodic microstructures on metallic alloy surfaces are fabricated with this technique. A method of preparing extended scale periodic microstructures by loading dynamic time-varying phases is also demonstrated. Scanning electron microscopy (SEM) reveals the period and morphology of the microstructures created using this technique. The asymmetry of interference modes generated from the beams with asymmetric wave vector distributions is equally explored. The flexibility of programming the period of the microstructures is demonstrated.

We perform plasmon-enhanced femtosecond laser ablation of silicon using gold nanorods to produce sub-diffraction limit features. While the observed hole shape seems inconsistent with calculated field distribution, we show that using a carrier diffusion-based model, both shape and depth of the nanoholes can be reliably explained. The laser energy is first deposited into electron-hole pairs that are created in the nanostructure's enhanced near-field. Those carriers then diffuse and transfer their energy to the silicon lattice, producing ablation. Increased importance of the carrier diffusion process is shown to arise from the extreme localization of the deposited energy around the nanostructure, due to the plasmonic effect. The characteristic shape of holes is revealed as a striking signature of the screened charge carriers-phonon coupling that is shown to channel the heat transfer to the lattice and control ablation.

A novel technique is introduced that dramatically increases the quality and spatial resolution of directly ablated periodic nanostructures on materials. The presented method utilizes a PMMA confinement layer spin coated on the surface of the ablated material reducing the violence and speed of expansion of the molten material. As a result, droplet formation deteriorating the achievable resolution can be completely avoided. Moreover, motion control of the molten material leads to structural details with dimensions well below the irradiation wavelength.

We demonstrate the improvement and formation of UV-induced damage on LBO crystal output surface during long-term (130 h) high-power (20 W) high-repetition-rate (80 kHz) third-harmonic generation. The output surface was super-polished (RMS surface roughness <0.6 nm) to sub-nanometer scale super smooth roughness. The surface lifetime has been improved more than 20-fold compared with the as-polished ones (RMS surface roughness 4.0~8.0 nm). The damage could be attributed to the consequence of thermal effects resulted from impurity absorptions. Simultaneously, it was verified that the impurities originated in part from the UV-induced deposition.

The surface localized polymer alignment (SLPA) method allows complete control of the polar pretilt angle as a function of position in liquid crystal devices. In this work, a liquid crystal (LC) cylindrical lens is fabricated by the SLPA method. The focal length of the LC lens is set by the polymerization conditions, and can be varied by a non-segmented electrode. The LC lens does not require a shaped substrate, or complicated electrode patterns, to achieve a desired parabolic phase profile. Therefore, both fabrication and driving process are relatively simple.

InGaN films with 33% and 60% indium contents were deposited by pulsed laser deposition (PLD) at a low growth temperature of 300 °C. The films were then annealed at 500-800 °C in the non-vacuum furnace for 15 min with an addition of N(2) atmosphere. X-ray diffraction results indicate that the indium contents in these two films were raised to 41% and 63%, respectively, after annealing in furnace. In(2)O(3) phase was formed on InGaN surface during the annealing process, which can be clearly observed by the measurements of auger electron spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. Due to the obstruction of indium out-diffusion by forming In(2)O(3) on surface, it leads to the efficient increment in indium content of InGaN layer. In addition, the surface roughness was greatly improved by removing In(2)O(3) with the etching treatment in HCl solution. Micro-photoluminescence measurement was performed to analyze the emission property of InGaN layer. For the as-grown InGaN with 33% indium content, the emission wavelength was gradually shifted from 552 to 618 nm with increasing the annealing temperature to 800 °C. It reveals the InGaN films have high potential in optoelectronic applications.