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The emphasis on climate change requires processes to be more efficient to minimize CO2 emissions, and nanostructured materials as catalysts could play a crucial role due to their high surface area per unit volume. Herein, we report the synthesis of silica microspheres (450–600 nm) using a modified Stober process, on which iron oxide clusters were deposited by sonolysis of iron pentacarbonyl to yield a nanostructured iron material (Si-Fe). A suite of spectroscopic techniques was used to characterize the synthesized materials. The BET surface area of freshly prepared Stober silica was 8.00 m2/g, and the Si-Fe material was 24.0 m2/g. Iron is commercially used as a Fischer–Tropsch (F–T) catalyst due to its low cost. However, catalyst attrition causes catalyst loss and lower product quality. In this study, the synthesized Si-Fe materials were evaluated for F–T synthesis to address these challenges. For comparison, two commercial materials, UCI (silica-supported micron-sized iron oxide) and BASF (unsupported nanosized iron oxide), were also evaluated. All three materials were first activated by pretreatment with either CO or synthesis gas (a mixture of CO and H2) for 24 h, then evaluated for quick screening in batch mode for F–T synthesis in a Parr batch reactor at three temperatures: 493 K, 513 K, and 533 K. The F–T data at 513 K showed that the CO-pretreated Si-Fe catalyst demonstrated lower CO2 (58%) C8–C20 selectivity (mol% C) to hydrocarbons, surpassing both reference catalysts. The temperature dependence data for Si-Fe: 17.4%, 58.3%, and 54.9% at 493 K, 513 K, and 533 K, respectively, showed that the hydrocarbon yield maximized at 513 K. The surface area increased to 27.9 m2/g for the CO-reduced Si-Fe catalyst after the F–T reaction at 513 K. The morphology and structural change of catalysts, before and after the F–T runs, were imaged. Of all the catalysts evaluated, the SEM–EDS data analysis showed the least carbon deposition on the CO-treated Si-Fe catalyst after the F–T reaction at 513 K and minimized CO2, a greenhouse gas. This could pave the way for selecting nanomaterials as F–T catalysts that effectively operate at lower temperatures and produce negligible CO2 by minimizing water-gas-shift (WGS) activity.

Plastic waste is an outstanding environmental thread. Poly (ethylene terephthalate) (PET) is one of the most abundantly produced single-use plastics worldwide, while its recycling rates are low. In parallel, additive manufacturing is a rapidly evolving technology with wide-ranging applications. Thus, there is a need for a broad spectrum of polymers to meet the demands of this growing industry and address post-use waste materials. This perspective article highlights the potential of designing microbial cell factories to upcycle PET into functionalized chemical building blocks for additive manufacturing. We present the leveraging of PET hydrolyzing enzymes and rewiring the bacterial C2 and aromatic catabolic pathways to obtain high-value chemicals and polymers. Since PET mechanical recycling back to original materials is cost-prohibitive, the biochemical technology is a viable alternative to upcycle PET into novel 3D printing materials, such as replacements for acrylonitrile butadiene styrene (ABS). The presented hybrid chemo-bio approaches potentially enable the manufacturing of environmentally friendly degradable or higher-value high-performance polymers and composites and their reuse for a circular economy.

Using a specially designed apparatus, which collects simultaneous temperature and X-ray scattering data, we performed in situ measurements of the filament during MatEx 3D printing. The data show that the MatEx 3D printing extrusion process provides sufficient shear to form shish-kebab structures, which initially nucleate at the filament surface and spread into the filament core. Time-resolved measurements show that the kebab component near the surface relaxes after deposition of the second filament and enhances chain diffusion across the interface. SEM images indicate near complete interfacial merging of the filaments, which results in excellent mechanical properties.

The scope of the work undertaken in this paper was to explore the feasibility and reliability of using the Raman signature of aromatic amino acids as a marker in the detection of the presence of breast cancer and perhaps, even the prediction of cancer development in very early stages of cancer onset. To be able to assess this hypothesis, we collected most recent and relevant literature in which Raman spectroscopy was used as an analytical tool in the evaluation of breast cell lines and breast tissue, re-analyzed all the Raman spectra, and extracted all spectral bands from each spectrum that were indicative of aromatic amino acids. The criteria for the consideration of the various papers for this study, and hence, the inclusion of the data that they contained were two-fold: (1) The papers had to focus on the characterization of breast tissue with Raman spectroscopy, and (2) the spectra provided within these papers included the spectral range of 500–1200 cm−1, which constitutes the characteristic region for aromatic amino acid vibrational modes. After all the papers that satisfied these criteria were collected, the relevant spectra from each paper were extracted, processed, normalized. All data were then plotted without bias in order to decide whether there is a pattern that can shed light on a possible diagnostic classification. Remarkably, we have been able to demonstrate that cancerous breast tissues and cells decidedly exhibit overexpression of aromatic amino acids and that the difference between the extent of their presence in cancerous cells and healthy cells is overwhelming. On the basis of this analysis, we conclude that it is possible to use the signature Raman bands of aromatic amino acids as a biomarker for the detection, evaluation and diagnosis of breast cancer.

As a rapidly growing area in materials design, the biomimetic approach at the frontier between biology and materials science aims to introduce advanced materials with structural diversities and functional versatilities by mimicking remarkable systems available in nature. Inspired by the fascinating nanostructured assembly existing in the cell walls of different plant species, we designed two fully bio-based green nanomaterials reinforced with renewable polysaccharide nanoparticles in the form of cellulose nanowhiskers (CNWs). In our initial design, the CNWs were incorporated into a cellulose acetate propionate matrix to form a bionanocomposite film, while in the second design the CNWs were entangled within a network of a collagenous medium to introduce a bionanocomposite hydrogel. Tensile and rheological measurements were carried out to study the system’s deformation as subjected to axial force or oscillatory shear. Biocompatibility was tested via incubation of human bone marrow-derived mesenchymal stem cells in vitro. Careful control of the processing conditions resulted in a three-dimensional rigid CNW network percolating within both biopolymer matrices, giving rise to an excellent performance at only a small fraction of CNWs at 3 wt.%. This study reveals that the fully bio-based green nanomaterials with enhanced mechanical percolation could construct a suitable platform for scaffolding in tissue engineering.

The use of surface-enhanced Raman spectroscopy (SERS) to delineate between the breast epithelial cell lines MCF10A, SK-BR-3, and MDA-MB-231 is explored utilizing varied morphologies of gold nanoparticles. The nanoparticles studied had spherical, star-like, and quasi-fractal (nanocaltrop) morphologies and possessed varying degrees of surface inhomogeneity and complexity. The efficacy of Raman enhancement of these nanoparticles was a function of their size, their surface morphology, and the associated density of "hot spots," as well as their cellular uptake. The spherical and star-like nanoparticles provided strong signal enhancement that allowed for the discernment among the three cell phenotypes based solely on the acquired Raman spectra. The presence of overlapping Raman band spectral regions, as well as unique spectral bands, suggests that the underlying biological differences between these cells can be accessed without the need for tagging the nanoparticles or for specific cell targeting, demonstrating the potential ubiquity of this technique in imaging any cancer. This work provides clear evidence for the potential application of SERS as a tool for mapping cancerous lesions, possibly during surgery and under histopathological analysis.

Quasi-fractal gold nanoparticles can be synthesized via a modified and temperature controlled procedure initially used for the synthesis of star-like gold nanoparticles. The surface features of nanoparticles lead to improved enhancement of Raman scattering intensity of analyte molecules due to the increased number of sharp surface features possessing numerous localized surface plasmon resonances (LSPR). The LSPR is affected by the size and shape of surface features as well as inter-nanoparticle interactions, as these affect the oscillation modes of electrons on the nanoparticle surfaces. The effect of the particle morphologies on the localized surface plasmon resonance (LSPR) and on the surface-enhancing capabilities of these nanoparticles is explored by comparing different nanoparticle morphologies and concentrations. We show that in a fixed nanoparticle concentration regime, quasi-fractal gold nanoparticles (gold nanocaltrop) provide the highest level of surface enhancement, whereas spherical nanoparticles provide the largest enhancement in a fixed gold concentration regime. The presence of highly branched features enables these nanoparticles to couple with a laser wavelength, despite having no strong absorption band and hence no single surface plasmon resonance. This cumulative LSPR may allow these nanoparticles to be used in a variety of applications in which laser wavelength flexibility is beneficial, such as in medical imaging applications where fluorescence at short laser wavelengths may be coupled with non-fluorescing long laser wavelengths for molecular sensing.

The synthesis of star-like gold nanoparticles (SGNs) in a temperature-controlled environment allows for temperature modulation and facilitates the growth of highly branched nanoparticles. By increasing the synthesis temperature, the level of branching increases as well. These highly branched features represent a distinctly novel, quasi-fractal nanoparticle morphology, referred to herein as gold nano caltrops (GNC). The increased surface roughness, local curvature and degree of inhomogeneity of GNC lend themselves to generating improved enhancement of the scattering signals in surface-enhanced Raman spectroscopy (SERS) via a mechanism in which the localized surface plasmon sites, or "hot spots," provide the engine for the signal amplification, rather than the more conventional surface plasmon. Here, the synthesis procedure and the surface-enhancing capabilities of GNC are described and discussed.

A bone graft is a complicated structure that provides mechanical support and biological signals that regulate bone growth, reconstruction, and repair. A single-component material is inadequate to provide a suitable combination of structural support and biological stimuli to promote bone regeneration. Multicomponent composite biomaterials lack adequate bonding among the components to prevent phase separation after implantation. We have previously developed a novel multistep polymerization and fabrication process to construct a nano-hydroxyapatite-poly(D,L-lactide-co-glycolide)-collagen biomaterial (abbreviated nHAP-PLGA-collagen) with the components covalently bonded to each other. In the present study, the mechanical properties and osteogenic potential of nHAP-PLGA-collagen are characterized to assess the material's suitability to support bone regeneration. nHAP-PLGA-collagen films exhibit tensile strength very close to that of human cancellous bone. Human mesenchymal stem cells (hMSCs) are viable on 2D nHAP-PLGA-collagen films with a sevenfold increase in cell population after 7 days of culture. Over 5 weeks of culture, hMSCs deposit matrix and mineral consistent with osteogenic differentiation and bone formation. As a result of matrix deposition, nHAP-PLGA-collagen films cultured with hMSCs exhibit 48% higher tensile strength and fivefold higher moduli compared to nHAP-PLGA-collagen films without cells. More interestingly, secretion of matrix and minerals by differentiated hMSCs cultured on the nHAP-PLGA-collagen films for 5 weeks mitigates the loss of mechanical strength that accompanies PLGA hydrolysis.

Complementary techniques were applied to characterize the structure property relationships of FDM printed isotactic polypropylene/graphene nanocomposites. Raman spectroscopy indicated that graphene was mostly exfoliated during the nozzle extrusion process. Rheological measurements of the viscosity indicated that the presence of graphene induced shear thinning during extrusion. Azimuthal scans of wide angle x-ray scattering indicate correlated thermal fluctuations of the graphene platelets which stops abruptly at the onset of transcrystallization, or templating of the iPP chains on the graphene. X-ray microbeam SAXS analysis show the formation of ‘shish-kebab’ structures at the core of the unfilled filaments, where the ‘kebab’ component vanishes at the fiber-fiber interface enabling interdiffusion. Weak lamellar structure, and a corresponding decrease in the storage modulus are observed with the addition of 5% graphene. The lamellar structure disappears entirely with the addition of 10% graphene, while the storage modulus is decreased by nearly 50%. Thermal imaging of heat flux dissipation across molded and printed samples shows no orientational effects in pure iPP despite differences in crystal structure. Thermal conductivity increases dramatically in the samples with 10% graphene, and strong orientational effects are observed where the thermal coefficients differ by 180% between samples printed parallel or perpendicular to the heat flux.

Quasi-fractal gold nanoparticles can be synthesized via a modified and temperature controlled procedure initially used for the synthesis of star-like gold nanoparticles. The surface features of nanoparticles leads to improved enhancement of Raman scattering intensity of analyte molecules due to the increased number of sharp surface features possessing numerous localized surface plasmon resonances (LSPR). The LSPR is affected by the size and shape of surface features as well as inter-nanoparticle interactions, as these affect the oscillation modes of electrons on the nanoparticle surfaces. The effect of the particle morphologies on the LSPR and further on the surface-enhancing capabilities of these nanoparticles is explored by comparing different nanoparticle morphologies and concentrations. We show that in a fixed nanoparticle concentration regime, Quasi-fractal gold nanoparticles provide the highest level of surface enhancement, whereas spherical nanoparticles provide the largest enhancement in a fixed gold concentration regime. The presence of highly branched features enables these nanoparticles to couple with a laser wavelength despite having no strong absorption band and hence no single surface plasmon resonance. This cumulative LSPR may allow these nanoparticle to be used in a variety of applications where laser wavelength flexibility is beneficial, such as in medical imaging applications where fluorescence at short laser wavelengths may be coupled with non-fluorescing long laser wavelengths for molecular sensing.

Orientation of cellulose nanowhiskers (CNWs) within various matrices is an effective approach that affords the exploitation of the high stiffness of CNWs as a reinforcement phase in nanocomposites. One potential engineering method to achieve orientation is to incorporate magnetic properties into the CNWs by tethering magnetic nanoparticles onto the surface of these nanoparticles, followed by their alignment in an externally-applied magnetic field. In this work we report the successful in-situ tethering of iron oxide nanoparticles (IONPs) onto CNWs by the thermal decomposition of Fe(CO)5 in a H2O/DMF suspension. Following this procedure, IONPs consisting of mixtures of Fe3O4 and Fe2O3 with an average diameter of 20 nm were attached to the CNWs. The type of iron oxide species that was generated was determined by selected area electron diffraction (SAED) and energy dispersive spectroscopy (EDS) and the particle size was evaluated by transmission electron microscopy (TEM). Raman spectroscopy was used to characterize the presence and the nature of the molecular interaction between the IONPs and the CNWs.

Mesoscale crumpled graphene oxide roses (GO roses) were synthesized by using colloidal graphene oxide (GO) variants as precursors for a hybrid emulsification/rapid evaporation approach. This process produced rose-like, spherical, reduced mesostructures of colloidal graphene oxide, with corrugated surfaces and particle sizes ranging from ~800 nm to 15 μm. The morphology and chemical structure of these produced GO roses was investigated using electron microscopy and spectroscopy techniques. The proposed synthesis route provides control over particle size, morphology and chemical properties of the synthesized GO roses.

We have developed a novel multicomponent nano-hydroxyapatite-poly(D,L-lactide-co-glycolide)-collagen biomaterial (nHAP-PLGA-collagen) with mechanical properties similar to human cancellous bone. To demonstrate the bone forming capacity of nHAP-PLGA-collagen prior to in vivo experiments, nHAP-PLGA-collagen films and 3D porous scaffolds were seeded with human mesenchymal stem cells (hMSCs) to characterize cell proliferation and osteogenic differentiation. Over 21 days hMSCs seeded on 2D nHAP-PLGA-collagen films proliferate, form nodules, deposit mineral and express high alkaline phosphatase activity (ALP) indicating commitment of hMSCs towards osteogenic lineage. When seeded in 3D scaffolds, hMSCs migrate throughout the connected porous network of the nHAP-PLGA-collagen scaffold and proliferate to fill the scaffold voids. Over 35 days, cells express ALP, osteocalcin and deposit minerals with kinetics similar to osteogenesis in vivo. Adipogenic or chondrogenic differentiation is not detected in 3D constructs, indicating that in an osteogenic environment the presence of bone ECM specific molecules in nHAP-PLGA-collagen scaffolds support homogeneous bone tissue development. This ability of nHAP-PLGA-collagen matrices to provide biochemical stimulation to support osteogenesis from stem cells along with its high mechanical strength suggests that nHAP-PLGA-collagen is a suitable biomaterial for bone regeneration. This platform technology of covalently attaching ECM proteins and molecules with synthetic and natural polymers to adjust material properties and biochemical signaling has a potential for a wider range of applications in tissue engineering and regenerative medicine.

In the synthesis of the microporous metal–organic framework copper 1,4-benzenedicarboxylate [Cu(BDC)], solvent exchange with methanol prior to recrystallization lowers the desolvation temperature to 160 °C and produces more crystalline Cu(BDC). The solution to the crystal structure of Cu(BDC) has been determined by using ab initio quantum molecular calculations and refinement with synchrotron X-ray powder diffraction data. This solution is in the P space group with a = 5.25 A, b = 9.67 A, c = 10.77 A, α = 90.29°, β = 91.06°, γ = 92.413°, and V = 546.04 A3. The Brunauer–Emmett–Teller (BET) surface area was 903 m2 g–1 with 777 m2 g–1 of micropore surface area. The uptake of CO2 and CH4 up to 20 bar were 5.2 and 2.7 mmol g–1, respectively. These values are compared to those of 1,3,5-benzenetricarboxylate [Cu3(BTC)2, HKUST-1] and used to show that the elevated metal-site density per unit volume is responsible for a proportionally higher uptake on the basis of relative surface areas. The platelike particles with perpendicular pores are promising candidates for mixed-matrix membranes.

Cellulose-based nanocomposites could potentially function as structural materials for prosthetic vascular conduits given their moldability, mechanical strength in the wet state, stability, and durability as well as their ability to integrate a nanofibrous porous network with superior structural diversity and functional versatility. In this study, we have developed a cellulose-based nanocomposite consisting of cellulose nanowhiskers (CNWs) embedded and aligned in a cellulose acetate propionate (CAP) matrix. When compared to non-biocompatible inclusions such as carbon nanotubes and Kevlar fillers, CNWs imparted significant strength and directional rigidity to the CNW-CAP composite even at 0.2 wt.%. In addition, a significant improvement in critical properties was observed when the CNWs were aligned in an externally-applied relatively weak magnetic field (0.3 T). Magnetically induced alignment not only improved the directionality and percolation limits of the nanoparticles within the medium, but also drastically lowered the optimum amount of CNWs required to obtain the best composite performance. Therefore, highly desirable properties can be induced in cellulose-based biocompatible composites by modifying the processing methods, with potential use as scaffolds for vascular tissue engineering of a small diameter graft.

Reduced graphene oxide (rGO) tethered with maghemite (γ-Fe2O3) was synthesized using a novel modified sol–gel process, where sodium dodecylbenzenesulfonate was introduced into the suspension to prevent the undesirable formation of an iron oxide 3D network. Thus, nearly monodispersed and homogeneously distributed γ-Fe2O3 magnetic nanoparticles could be obtained on surface of graphene sheets. The utilized thermal treatment process did not require a reducing agent for reduction of graphene oxide. The morphology and structure of the composites were investigated using various characterization techniques. As-prepared rGO/Fe2O3 composites were utilized as anodes for half lithium ion cells. The 40 wt.%-rGO/Fe2O3 composite exhibited high reversible capacity of 690 mA h g−1 at current density of 500 mA g−1 and good stability for over 100 cycles, in contrast with that of the pure-Fe2O3 nanoparticles which demonstrated rapid degradation to 224 mA h g−1 after 50 cycles. Furthermore, the composite showed good rate capability of 280 mA h g−1 at 10C (∼10,000 mA g−1). These characteristics could be mainly attributed to both the use of an effective binder, poly(acrylic acid) (PAA), and the specific hybrid structures that prevent agglomeration of nanoparticles and provide buffering spaces needed for volume changes of nanoparticles during insertion/extraction of Li ions.

Bone grafts, commonly performed to augment bone regeneration from autologous or alleogeneic sources, carry an enormous cost, estimated at upwards of 21 billion dollars per year. Hydroxyapatite (HAP) bio-ceramic has been widely used in clinic as a bone graft substitute material due to its biocompatibility and the similarity of its structure and composition to bone mineral. However, its applications are limited due to its lack of strength and toughness. Researchers have attempted to overcome these issues by combining HAP bio-ceramics into resorbable polymers to improve their mechanical properties. However, poor bonding between the HAP and the polymer caused separation at the polymer-filler interface. To overcome this, short chains of polymers were grafted directly from the hydroxyl groups on the surface of nanocrystalline HAP. Collagens, being the most abundant proteins in the body, and having suitable properties such as biodegradability, bioabsorbability with low antigenicity, high affinity to water, and the ability to interact with cells through integrin recognition, makes them a very promising candidate for the modification of the polymer surface. In this study, a novel method of synthesizing nano-hydroxyapatite (nHAP)-g-poly(lactide-co-glycolide)-g-collagen polymer was introduced. The synthesis process was carried out in several steps. First, poly (lactide-co-glycolide) (PLGA) polymer was directly grafted onto the hydroxyl group of the surface of n-HAP particles by ring-opening polymerization, and subsequently coupled with succinic anhydride. In order to activate the co-polymer for collagen attachment, the carboxyl end group obtained from succinic anhydride was reacted with N-hydroxysuccinimide (NHS) in the presence of dicyclohexylcarbodiimide (DCC) as the cross-linking agent. Finally, the activated co-polymer was attached to calf skin collagen type I, in hydrochloric acid/phosphate buffer solution and the precipitated co-polymer with attached collagen was isolated. The synthesis was monitored by 1H NMR and FTIR spectroscopies and the products after each step were characterized by thermal analysis (TGA and DSC). These composite materials will be tested as potential scaffolds for tissue engineering applications.

This paper examines the wetting characteristics of porous polyethylene surfaces modified by exposure to reactive oxygen glow discharge gas plasma, through the direct measurement of the wicking properties of the modified material. It is well-known that oxygen plasma can be used to chemically alter the surface of polyethylene to enhance wetting properties. Chemical and physical modification of a polymer's surface is the consequence of reactions initiated by the collision of high-energy species in the plasma with the polymer surface. The conditions of the plasma treatment, such as electric field strength (power), exposure time, and chamber pressure, govern the frequency and energy of collisions and, thus, determine the nature and degree of the chemical modification of the polyethylene surface. Comparisons of the chemical modification of sintered porous polyethylene surfaces achieved through treatments with reactive oxygen glow discharge gas plasmas generated at various powers, chamber pressures, and times of exposure were made by measuring the wicking rate of distilled and deionized water in the modified materials. A strong correlation was observed between the electric field power used to generate the plasma and the degree of chemical modification of the polyethylene surfaces. In addition, the rate of chemical modification was also found to be a function of the electric field power.

A series of Zn–Cu 1,4-benzenedicarboxylate(bdc) metal organic frameworks(MOF) have been synthesized by introducing N,N-dimethylformamide(DMF) solutions of 1,4-benzenedicarboxylic acid to metal salt solutions with a range of concentrations of Cu(NO3)2 and Zn(NO3)2 across the entire composition range. At the Zn-rich side of the range, the presence of Cu(II) had the effect of changing the polymorph of the solid from the predominantly P21/n structure, associated with MOF-2, to the C2/m structure, shared with Cu(bdc). There was an associated change in crystal morphology that accompanied the addition of a Cu salt impurity. BET surface area measurements of the thermally desolvated product showed that the surface area of the Zn(bdc) increased with the addition of Cu. At the Cu-rich side, magnetic susceptibility measurements indicated that the presence of the Zn impurity increased the fraction of paramagnetic Cu centers, suggesting the formation of a large fraction of heterometallic secondary building units(hSBU) ...

The microstructure and wettability of titanium (Ti) surfaces directly impact osteoblast differentiation in vitro and in vivo. These surface properties are important variables that control initial interactions of an implant with the physiological environment, potentially affecting osseointegration. The objective of this study was to use polyelectrolyte thin films to investigate how surface chemistry modulates response of human MG63 osteoblast-like cells to surface microstructure. Three polyelectrolytes, chitosan, poly(l-glutamic acid), and poly(l-lysine), were used to coat Ti substrates with two different microtopographies (PT, Sa = 0.37 µm and SLA, Sa = 2.54 µm). The polyelectrolyte coatings significantly increased wettability of PT and SLA without altering micron-scale roughness or morphology of the surface. Enhanced wettability of all coated PT surfaces was correlated with increased cell numbers whereas cell number was reduced on coated SLA surfaces. Alkaline phosphatase specific activity was increased on coated SLA surfaces than on uncoated SLA whereas no differences in enzyme activity were seen on coated PT compared to uncoated PT. Culture on chitosan-coated SLA enhanced osteocalcin and osteoprotegerin production. Integrin expression on smooth surfaces was sensitive to surface chemistry, but microtexture was the dominant variable in modulating integrin expression on SLA. These results suggest that surface wettability achieved using different thin films has a major role in regulating osteoblast response to Ti, but this is dependent on the microtexture of the substrate.

Magnetic carbon nanotubes (m-CNTs) were tethered with γ-Fe 2 O 3 nanoparticles that were formed via a novel modified sol-gel approach. These nanohybrid materials were readily aligned parallel to the direction of a magnetic field in polyethylene oxide (PEO) matrices under a relatively weak magnetic field. The composite films were characterized by XRD, and the crystallization kinetics of PEO in the presence of m-CNTs was measured by differential scanning calorimetry. The results indicated that the surface-tethered magnetic nanoparticles provided nucleation sites for the PEO crystal growth, while maintaining the spherulitic-shaped crystal morphology. The conductivity of the PEO-m-CNTs composite films increased with increasing m-CNTs content in the polymer matrix. Furthermore, the conductivities parallel to the direction of m-CNT alignment were higher than those in the perpendicular direction, indicating that the alignment of the m-CNTs contributed to the enhancement of the anisotropic electrical properties of the composites in the direction of alignment. The mechanical properties of the samples also show anisotropic behavior similar to that of the electrical properties.

Titanium (Ti) has been widely used as an implant material due to the excellent biocompatibility and corrosion resistance of its oxide surface. Biomaterials must be sterile before implantation, but the effects of sterilization on their surface properties have been less well studied. The effects of cleaning and sterilization on surface characteristics were bio-determined using contaminated and pure Ti substrata first manufactured to present two different surface structures: pretreated titanium (PT, Ra = 0.4 μm) (i.e. surfaces that were not modified by sandblasting and/or acid etching); (SLA, Ra = 3.4 μm). Previously cultured cells and associated extracellular matrix were removed from all bio-contaminated specimens by cleaning in a sonicator bath with a sequential acetone–isopropanol–ethanol–distilled water protocol. Cleaned specimens were sterilized with autoclave, gamma irradiation, oxygen plasma, or ultraviolet light. X-ray photoelectron spectroscopy (XPS), contact angle measurements, profilometry, and scanning electron microscopy were used to examine surface chemical components, hydrophilicity, roughness, and morphology, respectively. Small organic molecules present on contaminated Ti surfaces were removed with cleaning. XPS analysis confirmed that surface chemistry was altered by both cleaning and sterilization. Cleaning and sterilization affected hydrophobicity and roughness. These modified surface properties affected osteogenic differentiation of human MG63 osteoblast-like cells. Specifically, autoclaved SLA surfaces lost the characteristic increase in osteoblast differentiation seen on starting SLA surfaces, which was correlated with altered surface wettability and roughness. These data indicated that recleaned and resterilized Ti implant surfaces cannot be considered the same as the first surfaces in terms of surface properties and cell responses. Therefore, the reuse of Ti implants after resterilization may not result in the same tissue responses as found with never-before-implanted specimens.

Ideal outcomes in the field of tissue engineering and regenerative medicine involve biomaterials that can enhance cell differentiation and production of local factors for natural tissue regeneration without the use of systemic drugs. Biomaterials typically used in tissue engineering applications include polymeric scaffolds that mimic the 3-D structural environment of the native tissue, but these are often functionalized with proteins or small peptides to improve their biological performance. For bone applications, titanium (Ti) implants, or more appropriately the titania (TiO2) passive oxide layer formed on their surface, have been shown to enhance osteoblast differentiation in vitro and to promote osseointegration in vivo. In this study we evaluated the effect on osteoblast differentiation of pure TiO2 nano-fiber meshes with different surface micro-roughness and nano-fiber diameters, prepared by the electrospinning method. MG63 cells were seeded on TiO2 meshes, and cell number, differentiation markers and local factor production were analyzed. The results showed that cells grew throughout the entire surfaces and with similar morphology in all groups. Cell number was sensitive to surface micro-roughness, whereas cell differentiation and local factor production was regulated by both surface roughness and nano-fiber diameter. These results indicate that scaffold structural cues alone can be used to drive cell differentiation and create an osteogenic environment without the use of exogenous factors.

The local conformation of RNA molecules is an important factor in determining their catalytic and binding properties. The analysis of such conformations is particularly difficult due to the large number of degrees of freedom, such as the measured torsion angles per residue and the interatomic distances among interacting residues. In this work, we use a nearest-neighbor search method based on the statistical mechanical Potts model to find clusters in the RNA conformational space. The proposed technique is mostly automatic and may be applied to problems, where there is no prior knowledge on the structure of the data space in contrast to many other clustering techniques. Results are reported for both single residue conformations, where the parameter set of the data space includes four to seven torsional angles, and base pair geometries, where the data space is reduced to two dimensions. Moreover, new results are reported for base stacking geometries. For the first two cases, i.e., single residue conformations and base pair geometries, we get a very good match between the results of the proposed clustering method and the known classifications with only few exceptions. For the case of base stacking geometries, we validate our classification with respect to geometrical constraints and describe the content, and the geometry of the new clusters.

The success rate of titanium implants for dental and orthopedic applications depends on the ability of surrounding bone tissue to integrate with the surface of the device, and it remains far from ideal in patients with bone compromised by physiological factors. The electrical properties and electrical stimulation of bone have been shown to control its growth and healing and can enhance osseointegration. Bone cells are also sensitive to the chemical products generated during corrosion events, but less is known about how the electrical signals associated with corrosion might affect osseointegration. The metallic nature of the materials used for implant applications and the corrosive environments found in the human body, in combination with the continuous and cyclic loads to which these implants are exposed, may lead to corrosion and its corresponding electrochemical products. The abnormal electrical currents produced during corrosion can convert any metallic implant into an electrode, and the negative impact on the surrounding tissue due to these extreme signals could be an additional cause of poor performance and rejection of implants. Here, we review basic aspects of the electrical properties and electrical stimulation of bone, as well as fundamental concepts of aqueous corrosion and its electrical and clinical implications.

Titanium (Ti) osseointegration is critical for the success of dental and orthopaedic implants. Previous studies have shown that surface roughness at the micro- and submicro-scales promotes osseointegration by enhancing osteoblast differentiation and local factor production. Only relatively recently have the effects of nanoscale roughness on cell response been considered. The aim of the present study was to develop a simple and scalable surface modification treatment that introduces nanoscale features to the surfaces of Ti substrates without greatly affecting other surface features, and to determine the effects of such superimposed nano-features on the differentiation and local factor production of osteoblasts. A simple oxidation treatment was developed for generating controlled nanoscale topographies on Ti surfaces, while retaining the starting micro-/submicro-scale roughness. Such nano-modified surfaces also possessed similar elemental compositions, and exhibited similar contact angles, as the original surfaces, but possessed a different surface crystal structure. MG63 cells were seeded on machined (PT), nano-modified PT (NMPT), sandblasted/acid-etched (SLA), and nano-modified SLA (NMSLA) Ti disks. The results suggested that the introduction of such nanoscale structures in combination with micro-/submicro-scale roughness improves osteoblast differentiation and local factor production, which, in turn, indicates the potential for improved implant osseointegration in vivo.

Maghemite (γ-Fe 2 O 3 )/multi-walled carbon nanotubes (MWCNTs) hybrid-materials were synthesized and their anisotropic electrical conductivities as a result of their alignment in a polymer matrix under an external magnetic field were investigated. The tethering of γ-Fe 2 O 3 nanoparticles on the surface of MWCNT was achieved by a modified sol–gel reaction, where sodium dodecylbenzene sulfonate (NaDDBS) was used in order to inhibit the formation of a 3D iron oxide gel. These hybrid-materials, specifically, magnetized multi-walled carbon nanotubes (m-MWCNTs) were readily aligned parallel to the direction of a magnetic field even when using a relatively weak magnetic field. The conductivity of the epoxy composites formed in this manner increased with increasing m-MWCNT mass fraction in the polymer matrix. Furthermore, the conductivities parallel to the direction of magnetic field were higher than those in the perpendicular direction, indicating that the alignment of the m-MWCNT contributed to the enhancement of the anisotropic electrical properties of the composites in the direction of alignment.

In this work, we present a novel surface-mount placement process that could potentially overcome the inadequacies of the currently used stencil-printing technology, when applied to devices in which either their lateral and/or their horizontal dimensions approach the nanometric scale. Our novel process is based on the "bottom-up" design of an adhesive layer, operative in the molecular/nanoscale level, through the use of self-assembled monolayers (SAMs) that could form protective and conductive bridges between pads and components. On the basis of previous results, 1,4-phenylene diisocyanide (PDI) and terephthalic acid (TPA) were chosen to serve as the best candidates for the achievement of this goal. The quality and stability of these SAMs on annealed Cu surfaces (Rrms=0.15-1.1 nm) were examined in detail. Measurements showed that the SAMs of TPA and PDI molecules formed on top of Cu substrates created thermally stable organic monolayers with high surface coverage (∼90%), in which the molecules were closely packed and well-ordered. Moreover, the molecules assumed a standing-up phase conformation, in which the molecules bonded to the Cu substrate through one terminal functional group, with the other terminal group residing away from the substrate. To examine the ability of these monolayers to serve as "molecular wires," i.e., the capability to provide electrical conductivity, we developed a novel fabrication method of a parallel plate junction (PPJ) in order to create symmetric Cu-SAM-Cu electrical junctions. The current-bias measurements of these junctions indicated high tunneling efficiency. These achievements imply that the SAMs used in this study can serve as conductive molecular bridges that can potentially bind circuital pads/components.

Mixed matrix membranes (MMMs) for gas separations are traditionally comprised of zeolites dispersed in a polymer matrix in order to improve desired penetrant permeability and selectivity. Zeolites have a variety of drawbacks for this application – chiefly, a limited number of possible zeolite structures – that limit their potential for use in MMMs. Metal organic frameworks (MOFs), a relatively new class of microporous materials, are not well studied for use in MMMs. MOFs are an attractive alternative to the use of zeolites in MMMs because the number of possible structures is effectively infinite. In this work, a MOF of copper and terephthalic acid (CuTPA) was synthesized, characterized, and used to make MMMs. The gas transport properties of these CuTPA MMMs showed improvements over the pure polymer gas transport properties.

Unidirectional reinforced nanocomposite paper was fabricated from cellulose nanowhiskers and wood pulp under an externally applied magnetic field. A 1.2 Tesla magnetic field was applied in order to align the nanowhiskers in the pulp as it was being formed into a sheet of paper. The magnetic alignment was driven by the characteristic negative diamagnetic anisotropy of the cellulose nanowhiskers. ESEM micrographs demonstrated unidirectional alignment of the nanowhiskers in the all-cellulose composite paper. Comparing with control paper sheets made from wood pulp only, the storage modulus in the all-cellulose nanocomposites increased dramatically. The storage modulus along the direction perpendicular to the magnetic field was much stronger than that parallel to the magnetic field. This new nanocomposite, which contains preferentially oriented microstructures and has improved mechanical properties, demonstrates the possibility of expanding the functionality of paper products and constitutes a promising alternative to hydrocarbon based materials and fibers.

The use of diblock copolymers as chemical templates for the self-assembly of patterned and periodic materials has been the focus of extensive research in recent years. In this current work we show how a “one-pot” solution synthesis, which is based solely on the differences in the chemical reactivity of the two blocks towards metallic moiety, can be extended to create 1-, 2- and 3-dimensional ordered arrays of nanoparticles, conforming to the microstructure of the diblock copolymer. Chromium oxide nanoparticles (Cr 2 O 3 ) synthesized in a poly(styrene- b -methyl methacrylate) diblock copolymer solution form, after solvent evaporation and annealing, thin films consisting of a periodic composite material. We show that the preferential incorporation of the Cr 2 O 3 nanoparticles into the diblock copolymer through the direct polymer block – metal interactions does not hinder the self-assembly mechanism or the thermodynamically-driven microstructure formation of the diblock copolymer. Results show that the preferential segregation that occurred as early as the mixing stage of the reaction components was maintained throughout the annealing stage and the formation of the bulk ordered composite material.

In this work we describe a novel, facile method for the decoration of multiwalled carbon nanotubes (MWNTs) with nearly monodisperse γ-Fe2O3 magnetic (maghemite) nanoparticles and their alignment in a magnetic field. The tethering of the nanoparticles was achieved by the initial activation of the surface of the MWNTs with carboxylic acid groups, followed by the attachment of the γ-Fe2O3 nanoparticles via their synthesis using a modified sol−gel process. Sodium dodecylbenzenesulfonate (NaDDBS) was introduced into the suspension as a surfactant in order to prevent the formation of an iron oxide 3D network. Various characterization methods were used to confirm the formation of well-defined maghemite nanoparticles and show that they were tethered to the walls of the MWNTs. The tethered γ-Fe2O3 nanoparticles imparted magnetic characteristics to the MWNTs and allowed their alignment in the direction of an externally applied magnetic field. This facile alignment of MWNTs could promote the enhancement of various p...

The weak physical gelation of cellulose acetate propionate–butyl butyrate solutions as a result of the in-situ decomposition of iron pentacarbonyl complexes was explored. Viscometry and infrared spectroscopy were used to monitor the iron pentacarbonyl decomposition reaction progress and its effect on viscosity. Changes in viscosity in of the cellulosic fluids in general and gelation in particular were found to be dependent upon the environment in which the Fe(CO) 5 decompositions occurred. Systems under inert atmospheres exhibited a marked increase in viscosity, while systems under oxidative atmospheres exhibited a general decrease in viscosity. We propose a hypothesis that explains the dependence of the viscosity of these cellulosic fluids as a function of the environmental conditions during the precursor decomposition. Under nitrogen atmospheres, zero-valent nanoparticles with highly reactive surfaces are synthesized, which form weak, transient bonds with the cellulosic polymer. The iron particles, under these circumstances, serve as weak bridges between adjacent polymer chains. Conversely, the primary particles synthesized under an oxidative atmosphere are metal oxides, which are less attractive to the polymer chain and, therefore, do not yield such bridges. This work demonstrates the capability to apply a simple method to control the viscosity of cellulose ester fluids.

An investigation of the optical and magnetic properties of a unique hydrogen-linked conjugate nanostructure, comprised of superparamagnetic gamma-Fe(2)O(3) nanoparticles (NPs) and near-infrared PbSe nanocrystal quantum dot (NQD) chromophores, is reported. The results show retention of the NQDs' emission quantum efficiency and radiative lifetime, and only a small red shift of its band energy, upon conjugation to the dielectric surroundings of gamma-Fe(2)O(3) NPs. The study also shows the sustainability of the superparamagnetism of the NPs after conjugation, with only a slight decrease of the ferromagnetic-superparamagnetic transition temperature with respect to that of the individual NPs. Thus, the conjugate nanostructure can be considered as a useful medical platform when PbSe NQDs act as fluorescent tags, while the gamma-Fe(2)O(3) NPs are used as a vehicle driven by an external magnetic field for targeted delivery of tags or drugs.

In this paper, we report on a high-throughput (gram quantities) solvothermal method for the synthesis of copper terephthalate metal–organic frameworks in dmf. While the structure of MOF-2 and some of the associated polymorphs are well known, we know of no equivalent structural studies for the isostructural copper terephthalate (Cu–tpa). The material we have made crystallizes in the C2/m space group. Cu–tpa also exhibits reversible solvent-exchange properties. These properties make this material useful for potential applications in gas storage and catalysis applications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The self-assembly and selective distribution of metal or metal oxide nanoparticles in block copolymer matrices was designed to produce photonic bandgap materials through a bottom-up method rather than the more common top-down approach. The synthesis of such materials consists of the in situ thermolysis of metal carbonyl precursors in a diblock copolymer solution. Reaction rates of the formation of nanoparticles in solution were measured to better understand and control the course and final products of the reactions. Our results showed that the rates for reactions performed in a diblock copolymer solution are much faster than the rates of the same reactions performed in a homopolymer solution. The reaction rates for the thermolysis of three different metal carbonyl precursors, Cr(CO)6, Fe(CO)5, and Co2(CO)8, show that this phenomenon is not specific to the type of metal carbonyl precursor, but rather, to the type of polymer in solution. Polystyrene (PS) and poly(methyl methacrylate) (PMMA) were used as a m...

In this work, we employed an in situ polymerization approach to produce polyfurfuryl alcohol (PFA) nanocomposites without the use of solvents or surfactants. On the one hand, furfuryl alcohol (FA) has a dual function, serving both as an effective dispersant for the cellulose whisker (CW) and montmorillonite clay (MMT) nanoparticles and as the matrix precursor for the in situ polymerization. On the other hand, the CW and MMT nanoparticles also serve multiple functions, by first catalyzing the polymerization of FA, and then acting as an effective matrix modifier, increasing the thermal stability of the consolidated PFA nanocomposite. In the case of CW-PFA nanocomposites, the polymerization is catalyzed by sulfonic acid residues at the CW surface, left over from the whisker preparation. In the case of MMT-PFA nanocomposites, the polymerization is catalyzed by Lewis acid sites inherent to the MMT surface. Thermal analysis showed that both types of polymer nanocomposites (PNCs) were characterized by significan...

In this work, we probed the effects of a common surfactant, sodium dodecylbenzene sulfonate (NaDDBS), on the particle size of iron (III) oxides formed via a modified sol–gel synthesis. The goal was to create tunable nanosized particles via a method that combines the efficiency and advantages of the sol–gel process, but inhibits the formation of a gel. Two different metal salt precursors were used, ferric nitrate nonahydrate, Fe(NO 3 ) 3 · 9H 2 O, and ferric chlorate hexahydrate, FeCl 3 · 6H 2 O. The particle size of the dried gel was 4.5 nm for Fe(NO 3 ) 3 · 9H 2 O and 3.6 nm for FeCl 3 · 6H 2 O. In the presence of the surfactant FeCl 3 · 6H 2 O formed a gel and Fe(NO 3 ) 3 · 9H 2 O was unable to gel, but the new particle sizes were 4.9 nm and 3.2 nm, respectively. The addition of the surfactant in the later stages of the process afforded the stabilization of independent nanoparticles of the same size as those obtained in the systems that gelled.

In this paper, we have developed a geometric-based scaling model that describes the adsorption of diblock copolymer chains from good solvents and theta-solvents onto reactive surfaces of varying curvatures. To evaluate the impact of particle size on the adsorption process, we probed the adsorption of poly(styrene-b-methymethacrylate) (PS-PMMA) diblock copolymers from solvents with different degrees of selectivity on aluminum oxide (Al(2)O(3)) surfaces belonging to particles of different sizes. When the adsorbed PMMA layer is dense enough (in the case of a theta-solvent for the PMMA block), our results show good correlation between the theory and experimental results, pointing to the formation of a PMMA adsorption layer and a brushlike PS layer. Conversely, when adsorption occurs from a nonpreferential solvent, particularly on particles with high curvature, the PMMA adsorption layer at the surface becomes less dense and the grafted PS moiety exhibits a transitional morphology consisting of several layers of increasingly sparsely spaced blobs.

Water-soluble PbSe semiconductor quantum dots (QDs) with near-infrared absorption of 1100–2520 nm (corresponding to a diameter of 3–13 nm) were synthesized using 2-aminoethanthiol (AET). The oleic acid-stabilizing ligands used in the traditional synthesis of PbSe were exchanged with the 2-AET ligands, which promoted the solubilization of the QDs in an aqueous medium. This occurred due to the attraction of the surrounding water molecules to the exposed amino group, thus allowing the particles to reside in the water environment. The water-soluble PbSe QDs have very narrow size distribution (σ ≈ 4.5–5.5%). Transmission electron microscopy, spectrophotometric measurements, and Fourier transform infrared spectroscopy indicate that the morphology, size, size distribution, and chemical composition of the PbSe QDs remained unchanged during the transfer to an aqueous medium. In conclusion, the ability to synthesize water-soluble PbSe QDs with stable properties and uniform size distribution will allow them to have substantial advantages for biological applications such as biosensors and drug delivery.

The synthesis of metal nanoclusters in a polymeric environment has been shown to yield nearly monodisperse particles, whose size is controlled by the strength of the polymer/metal interactions. Although the phenomenon is quite general, little is known regarding the mechanism by which the polymer controls nanocluster size. Previous studies of the kinetics of nanocluster growth in polymeric melts above the glass transition temperature (Tg) suggest that the nanoparticle size is set by the critical cluster size (nucleation stage) rather than the rate of metal precursor transport, namely, growth. In this paper, we examine the kinetics of iron oxide (Fe2O3) nanocluster formation below the glass temperature (Tg) in two polymer melts: polystyrene (PS) and poly(methyl methacrylate) (PMMA). We find that the morphology of the nanoclusters formed below Tg is highly sensitive to the system temperature and differs significantly from the morphology above Tg. However, the kinetics of cluster formation is exponential wit...

Qualitative and quantitative studies of the oxidation of polycrystalline copper (Cu) thin films upon exposure to ambient air conditions for long periods (on the order of several months) are reported in this work. Thin films of Cu, prepared by thermal evaporation, were analyzed by means of X-ray photoelectron spectroscopy (XPS) to gain an understanding on the growth mechanism of the surface oxide layer. Analysis of high-resolution Cu LMM, Cu2p3/2, and O1s spectra was used to follow the time dependence of individual oxide overlayer thicknesses as well as the overall oxide composite thickness. Transmission electron microscopy (TEM) and spectroscopic ellipsometry (SE) were used to confirm the results obtained from XPS measurements. Three main stages of copper oxide growth were observed: (a) the formation of a Cu2O layer, most likely due to Cu metal ionic transport toward the oxide−oxygen interface, (b) the formation of a Cu(OH)2 metastable overlayer, due to the interactions of Cu ions with hydroxyl groups pr...