We describe the fabrication of filamentous hydrogel nanoparticles using a unique soft lithography based particle molding process referred to as PRINT (Particle Replication in Non-wetting Templates). The nanoparticles possess a constant width of 80 nm, and we varied their lengths ranging from 180 nm to 5000 nm. In addition to varying the aspect ratio of the particles, the deformability of the particles was tuned by varying the cross-link density within the particle matrix. Size characteristics such as hydrodynamic diameter and persistence length of the particles were analyzed using dynamic light scattering and electron microscopy techniques, respectively, while particle deformability was assessed by atomic force microscopy. Additionally, the ability of the particles to pass through membranes containing 0.2 μm pores was assessed by means of a simple filtration technique, and particle recovery was determined using fluorescence spectroscopy. The results show that particle recovery is mostly independent of aspect ratio at all cross-linker concentrations utilized, with the exception of 96 wt% PEG diacrylate 80 x 5000 nm particles, which showed the lowest percent recovery.

Highly-ordered silver nanovoid arrays are fabricated on porous anodic alumina membranes to produce robust and cost-efficient surface-enhanced Raman scattering (SERS) substrates. Plasmonic tunability can be accomplished by adjusting the topography with different anode voltages. Evenly distributed plasmonic fields, high average enhancement factor, and excellent ambient stability due to the natural protective layer are some of the unique advantages and the silver nanovoid arrays are applicable to sensing devices.

The liquid repellence and surface topography characterstics of coatings comprising a sprayed-on mixture of fluoroalkyl-functional precipitated silica and a fluoropolymer binder were examined using contact and sliding angle analysis, electron microscopy, and image analysis for determination of fractal dimensionality. The coatings proved to be an especially useful class of liquid repellent materials due to their combination of simple and scalable deposition process, low surface energy, and the roughness characteristics of the aggregates. These characteristics interact in a unique way to prevent the build-up of binder in interstitial regions, preserving re-entrant curvature across multiple length scales and thereby enabling a wide range of liquid repellency, including superoleophobicity. In addition, rather than accumulating in the interstices, the binder becomes widely distributed across the surface of the aggregates, enabling a mechanism in which a simple shortage or excess of binder controls the extent of coating roughness at very small length scales, thereby controlling the extent of liquid repellence.

The conserved nucleotide binding site (NBS), found on the Fab variable domain of all antibody isotypes, remains a not-so-widely known and unutilized site. Here, we describe a UV photocrosslinking method (UV-NBS) that utilizes the NBS for oriented immobilization of antibodies onto surfaces, such that the antigen binding activity of the antibody remains unaffected. Indole butyric acid (IBA) has affinity for the NBS with a Kd ranging from 1 to 8 µM for different antibody isotypes, and can be covalently photocrosslinked to the antibody at the NBS upon exposure to UV light. Using the UV-NBS method, antibody was successfully immobilized on synthetic surfaces displaying IBA via UV photocrosslinking at the NBS. An optimal UV exposure of 2 J/cm2 yielded significant antibody immobilization on the surface with maximal relative antibody activity per immobilized antibody without any detectable damage to antigen binding activity. Comparison of UV-NBS method with two other commonly used methods, ε-NH3+ conjugation and physical adsorption, demonstrated that UV-NBS method yields surfaces with significantly enhanced antigen detection efficiency, higher relative antibody activity, and improved antigen detection sensitivity. Taken together, the UV-NBS method provides a practical, site-specific surface immobilization method, with significant implications in the development of a large array of platforms with diverse sensor and diagnostic applications.

Edge effect is known to hinder a sessile drop's spreading. However, the underlying thermodynamic mechanisms responsible for the edge effect still have not been well understood. In this study, a free energy model has been developed to investigate energetic state of drops on a single pillar (from upright frustum to inverted frustum geometries). An analysis of drop free energy levels before and after crossing the edge allows us to understand the thermodynamic origin of edge effect. In particular, four wetting cases for a drop on a single pillar with different edge angles have been determined by understanding the characteristics of FE plots. A wetting map describing the four wetting cases is given in terms of edge angle and intrinsic contact angle. The results show that the free energy barrier observed near the edge plays an important role in determining the drop states, i.e. 1) stable or metastable drop states at the pillar's edge; 2) drop collapse by liquid spilling over the edge completely or staying at an intermediate sidewall position of the pillar. This thermodynamic model presents an energetic framework to describe the functioning of the so-called "re-entrant" structures. Results show good consistence with the literature and expand the current understanding of Gibbs' inequality condition.

A comparative study of PTFE surfaces treated by the post-discharge of He and He-O2 plasmas at atmospheric pressure is presented. The characterization of treated-PTFE surfaces and the species involved in the surface modification are related. In pure He plasmas, no significant change of the surface has been observed by XPS, dWCA and AFM, in spite of important mass losses recorded. According to these observations, a layer-by-layer physical etching without any preferential orientation is proposed, where the highly energetic helium metastables are the main species responsible for the scission of -(CF2)n- chains. In He-O2 plasmas, as the density of helium metastables decreases as function of oxygen flow rate, the treatment leads to fewer species ejected from the PTFE surfaces (in agreement with mass loss measurements and the detection of fluorinated species onto an aluminium foil). However, the dWCA and AFM measurements show an increase in the hydrophobicity and the roughness of the surface. The observed alveolar structures are assumed to be caused by an anisotropic etching where the oxygen atoms etch mainly the amorphous phase.

Controlled self-assembly of amphiphilic cyclodextrin is always a challenging topic in the field of supramolecular chemistry, since it provides the spontaneous generation of a well-defined aggregation with functional host sites with great potential applications in drug-carrier systems. β-Cyclodextrin modified with an anthraquinone moiety (1) was successfully synthesized. In the aqueous solution, 1 was found to be able to self-assemble into vesicles, which was characterized in detail by TEM, SEM, EFM and DLS. The formation mechanism of the vesicles was suggested based on the 2D ROESY and UV-vis results, and further verified by the MD simulation. Subsequently, the stimuli response property of the vesicles, including to Cu2+ and H+, was also studied. The vesicles can efficiently load Paclitaxel inside the membrane with functional macrocyclic cavities available, which can further carry small molecules, such as ferrocene. The vesicles loaded with Paclitaxel have remarkable anticancer effects. This work will provide new strategy in drug-carrier systems and tumor treatment methods.

We report a simple solvothermal synthesis approach to the growth of CuInS(2) nanocrystals with zincblende- and wurtzite-phase structures. Zincblende nanocrystals with particle sizes of 10-20 nm were produced using oleylamine as the solvent. When ethylenediamine was used as the solvent, similarly sized wurtzite nanocrystals with some degree of particle aggregation were formed. Use of a mixture of these solvents gave products with mixed phases including some polyhedral nanostructures. The crystal phases of these nanocrystals were carefully determined by X-ray diffraction and transmission electron microscopy analysis. All the samples exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1300 nm. Pure-phase zincblende and wurtzite CuInS(2) nanocrystals were employed as ink in the fabrication of solar cells. The spray-coated nanocrystal layer was subjected to a selenization process. A power conversion efficiency of ∼0.74% and a good external quantum efficiency profile over broad wavelengths have been measured. The results demonstrate that wurtzite and zincblende CuInS(2) nanocrystals may be attractive precursors to light-absorbing materials for making efficient photovoltaic devices.

Large-pore ethenylene-bridged (-CH=CH-) and phenylene-bridged (-C6H4-) periodic mesoporous organosilicas (PMOs) with face-centered-cubic structure (Fm3m symmetry) of spherical mesopores were synthesized at 7 °C at low acid concentration (0.1 M HCl) using Pluronic F127 triblock copolymer surfactant in presence of aromatic swelling agents (1,3,5-trimethylbenzene, xylenes - isomer mixture, and toluene). In particular, this work reports an unprecedented block-copolymer-templated well-ordered ethenylene-bridged PMO with cubic structure of spherical mesopores, and an unprecedented block-copolymer-templated face-centered cubic phenylene-bridged PMO, which also has an exceptionally large unit-cell size and pore diameter. The unit-cell parameters of 30 and 25 nm, and the mesopore diameters of 14 and 11 nm (nominal BJH-KJS pore diameters of 12-13 and 9 nm) were obtained for ethenylene-bridged and phenylene-bridged PMOs, respectively. Under the considered reaction conditions, the unit-cell parameters and pore diameters were found to be similar when the three different methyl-substituted benzene swelling agents were employed, although the degree of structural ordering appeared to improve for phenylene-bridged PMOs in the sequence of decreased number of methyl groups on the benzene ring.

We report a facile approach to the conjugation of protein-encapsulated gold fluorescent nanoclusters to the iron oxide nanoparticles through catechol reaction. This method eliminates the use of chemical linkers and can be readily extended to the conjugation of biological molecules and other nanomaterials onto nanoparticle surfaces. The key to the success was producing water soluble iron oxide nanoparticle with active catechol groups. Further, advanced electron microscopy analysis of the integrated gold nanoclusters and iron oxide nanoparticles provided direct evidence of the presence of a single fluorescent nanocluster per protein template. Interestingly, the integrated nanoparticles exhibited enhanced fluorescent emission in biological media. These studies will provide significantly practical value in chemical conjugation, the development of multifunctional.

The phase separation mechanism in semi-dilute aqueous poly(N-isopropylacrylamide)(PNIPAM) solutions is investigated with small angle neutron scattering (SANS). The nature of the phase transition is probed in static SANS measurements and with time dependent SANS measurements after a temperature jump. The observed critical exponents of the phase transition describing the temperature dependence of the Ornstein-Zernicke amplitude and correlation length are smaller than values from mean field theory. Time dependent SANS measurements show that the specific surface decreases with increasing time after a temperature jump above the phase transition. Thus, the formation of additional hydrogen bonds in the collapsed state is a kinetic effect: A certain fraction of water remains as bound water in the system. Moreover, H-D exchange reactions observed in PNIPAM have to be taken into account.

A detailed analysis of the cooperative two-electron transfer of surface-confined cytochrome c peroxidase (CcP) in contact with pH 6.0 phosphate buffer solution has been undertaken. This investigation is prompted by the prospect of achieving a richer understanding of this biologically important system via the employment of kinetically sensitive, but background devoid, higher harmonic components available in the large-amplitude Fourier transform ac voltammetric method. Data obtained from conventional dc cyclic voltammetric method are also provided for comparison. Theoretical considerations based on both ac and dc approaches are presented for cases where reversible or quasi-reversible cooperative two-electron transfer involves variation in the separation of their reversible potentials, including potential inversion (as described previously for solution phase studies). Comparison is also made with respect to the case of a simultaneous two-electron transfer process that is unlikely to occur in the physiological situation. Theoretical analysis confirms that the ac higher harmonic components provide greater sensitivity to the various mechanistic nuances that can arise in two electron surface-confined processes. Experimentally, the ac perturbation with amplitude and frequency of 200 mV and 3.88 Hz, respectively was employed to detect the electron transfer when CcP is confined to the surface of a graphite electrode. Simulations based on cooperative two-electron transfer with the employment of reversible potentials of 0.745±0.010 V, heterogeneous electron transfer rate constants of between 3 and 10 s(-1) and charge transfer coefficients of 0.5 for both processes satisfactorily fitted experimental data for the fifth to eighth ac harmonics. Imperfections in theory-experiment comparison are consistent with kinetic and thermodynamic dispersion and other non-idealities not included in the theory used to model the voltammetry of surface-confined CcP.

In this work, a new antifouling silica hydrogel was developed for potential biomedical applications. A zwitterionic polymer, poly(carboxybetaine methacrylate)(pCBMA), was produced via atom transfer radical polymerization and was appended to the hydrogel network in a two-step acid-base catalyzed sol-gel process. The pCBMA silica aerogels were obtained by drying the hydrogels under supercritical conditions using CO2. To understand the effect of pCBMA on gel structure, pCBMA silica aerogels with different pCBMA content were characterized using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy, and surface area from Brauner-Emmet-Teller (BET) measurements. The antifouling property of pCBMA silica hydrogel to resist protein (fibrinogen) adsorption was measured using enzyme-linked immunosorbent assay (ELISA) methods. SEM images revealed that particle size and porosity of the silica network decreased at low pCBMA content and increased at above 33 wt% of the polymer. The presence of pCBMA increased the surface area of the material by 91% at a polymer content of 25 wt%. NMR results confirmed that pCBMA was incorporated completely into the silica structure at polymer content below 20 wt%. Protein adsorption test revealed a reduction of fibrinogen adhesion by 83% at 25 wt% pCBMA content in the hydrogel compared to the unmodified silica hydrogel.

Electrical and mechanical properties of Dermatan Sulfated (DS) molecules are studied in aqueous environment as a function of pH. DS molecules linked at various points distributed on the surface of mica previously silanizated along with a suitable functionalized microsphere, attached to the cantilever of the atomic force microscope (AFM), provided suitable surfaces for testing interactions through the colloidal probe methodology. The repulsive force between the surfaces indicated that the charge of DS increases with pH as a result of the gradual deprotonation of acidic groups. Pulling experiments revealed increasing adhesion of DS to the monolayer as a function of pH, presumably due both to the electrical nature of the interaction between these molecules and the progressive increase of the charge of DS with pH. Serrations exhibited by the force in pulling experiments indicate that more than a single DS molecule is stretched at the same time. In addition, pulling force remained significant even at extensions that went beyond the average contour length of a single DS molecule which suggests the existence of significant link between DS molecules.

The nanofiber surface modified with physical or chemical gradients is very useful in a wide range of areas including tissue engineering, regenerative medicine, drug screening and biomaterial chemistry. In this work, we presented a novel and straightforward microfluidic assisted approach to produce electrospining nanofibers containing gradients in different compositions, nanoparticles and biomolecule concentrations. The series of gradient nanofibers were mainly produced by using a two inlet microfluidic device in combination with an electrospinning nozzle on a 3-D controllable platform, which exhibited different functions and properties. The controlled nanofibers with incorporated biomolecule gradient were used for guiding the spatial differentiation in mesenchymal stem cells (MSCs). This established approach is very simple, and flexible to operate, which might find enormous potentials for biology and tissue engineering applications.

We describe a simple method for synthesizing superparamagnetic nanoparticles (SPIONs) as small, stable contrast agents for magnetic resonance imaging (MRI) based on sulfobetaine zwitterionic ligands. SPIONs synthesized by thermal decomposition were coated with zwitterions to impart water dispersibility and high in vivo stability through the nanoemulsion method. Zwitterion surfactant coating layers are formed easily on oleic acid stabilized SPIONs via hydrophobic and van der Waals interactions. Our zwitterion coated SPIONs (ZSPIONs) had ultra-thin (~5 nm) coating layers with mean sizes of 12.0 ± 2.5 nm, measured by dynamic light scattering (DLS). Upon incubation in 1 M NaCl and 10% FBS, the ZSPIONs showed high colloidal stabilities without precipitating, as monitored by DLS. The T2 relaxivity coefficient of the ZSPIONs, obtained by measuring the relaxation rate based on the iron concentration was 261 mM-1s-1. This value was much higher than that of the commercial T2 contrast agent due to ultra-thin coating layer. Furthermore, we confirmed that ZSPIONs can be used as MR contrast agents for in vivo applications such as tumor imaging and lymph node mapping.

Self-assembled monolayers inherently possess polarizable dielectric components. In contact with a solution phase, these components are present in addition to the more generalized framework of non faradaic processes encompassing double layer capacitance and electrolyte resistance. The presence of such films, then, introduces additional capacitative and resistive terms that can have a profound impact of subsequently observed electronic characteristics but are not directly resolvable by standard electrochemical means. A capacitive analysis of such interfaces (Self-assembled Monolayer Capacitance Spectroscopy), introduced here, enables a clean mapping of these features and additionally presents a means of studying layer polarisability and Cole-Cole relaxation effects. The resolved resistive term contributes directly to an intrinsic monolayer uncompensated resistance that has a linear dependence on layer thickness. The dielectric model proposed is fully aligned with the classic Helmholtz plate capacitor model and additionally explains their inherently associated resistive features.

Coupling magnetic materials to plasmonic structures provides a pathway to increase dramatically the magneto-optical response of the resulting composite architecture. Although such optical enhancement has been demonstrated in a variety of systems, some basic aspects are scarcely known. In particular, reflectance/transmission modulations and electromagnetic field intensification -both triggered by plasmon excitations- can contribute to the magneto-optical enhancement. However, a quantitative evaluation of the impact of both factors on the magneto-optical response is lacking. To address this issue, we have measured magneto-optical Kerr spectra on corrugated gold/dielectric interfaces with magnetic (nickel and iron oxide) nanoparticles. We find that the magneto-optical activity is enhanced by up to an order of magnitude for wavelengths that are correlated to the excitation of propagating or localized surface plasmons. Our work sheds light on the fundamental principles for the observed optical response and demonstrates that the outstanding magneto-optical performance is originated by the increase of the polarization conversion efficiency, whereas the contribution of reflectance modulations is negligible.

A fundamental and systematic study on the fabrication of a supramolecularly assembled nanostructure of an organic ligand-capped CdS nanocrystal (NC) and multiple heptamine β-cyclodextrin ((NH2)7βCD) molecules in aqueous solution has been here reported. The functionalization process of pre-synthesized hydrophobic CdS NCs by means of (NH2)7βCD has been extensively investigated by using different spectroscopic and structural techniques, as function of different experimental parameters, such as the composition and the concentration of CD, the concentration of CdS NCs, the nature of the NC surface capping ligand (oleic acid and octylamine), and the organic solvent. The formation of a complex based on the direct coordination of the (NH2)7βCD amine groups at the NC surface has been demonstrated and found responsible for the CdS NC phase transfer process. The amine functional group in (NH2)7βCD and the appropriate combination of pristine capping agent coordinating the NC surface, and a suitable solvent have been found decisive for the success of the CdS NC phase transfer process. Furthermore, a layer-by-layer assembly experiment has indicated that the obtained (NH2)7βCD functionalized CdS NCs are still able to perform the host-guest chemistry. Thus, they offer a model of a nanoparticle-based material with molecular receptors, useful for bio applications.

This work investigates the effect of gold nanoparticles'(AuNPs) addition to paper substrate and examines the ability of these composite materials to amplify the Surface Enhanced Raman Scattering (SERS) signal of a dye adsorbed. Paper has a three dimensional (3D), porous and heterogeneous morphology. The manner in which paper adsorbs the nanoparticles is crucial to its SERS properties, particularly with regards to aggregation. In this work, we sought to maintain the same degree of aggregation, whilst changing the concentration of nanoparticles deposited on paper. We achieved this by dipping paper into AuNP solutions of different, known concentration and found that the initial packing density of AuNPs in solutions was retained on paper with the same degree of aggregation. The surface coverage of AuNPs on paper was found to scale linearly to their concentration profile in solutions. The SERS performances of the AuNPs-treated papers were evaluated with 4-aminothiophenol (4-ATP) as the Raman molecule, and their SERS intensities increased linearly with the AuNPs' concentration. Compared to AuNPs-treated silicon, the Raman enhancement factor (EF) from paper was relatively higher due to a more uniform and greater degree of adsorption of AuNPs. The effect of the spatial distribution of AuNPs in their substrates on SERS activity was also investigated. In this experiment, the number of AuNPs was kept constant (a 1µL droplet of AuNPs was deposited on all substrates), and the distribution profile of AuNPs was controlled by the nature of the substrate; paper, silicon and hydrophobized paper. The AuNP droplet on paper showed the most reproducible and sensitive SERS signal. This highlighted the role of the z-distribution (through film) of AuNPs within the bulk of the paper, producing a 3-dimensional (3D) multilayer structure to allow inter- and intralayer plasmon coupling, and hence amplifying the SERS signal. The SERS performance of nanoparticles-functionalized paper can thus be optimized by controlling the 3D distribution of the metallic nanoparticles, and such control is critical if these systems are to be implemented as a low-cost and highly sensitive bioassay platform. Keywords: SERS, gold nanoparticles (AuNPs), paper, heterogeneity, 3-dimensional, amplification, sensitivity, bioassay.