Table of contents

In this study, we have developed a novel carrier, micelle-type bioconjugated PLGA-4-arm-PEG branched polymeric nanoparticles (NPs), for the detection and treatment of pancreatic cancer. These NPs contained 4-arm-PEG as corona, and PLGA as core, the particle surface was conjugated with cyclo(arginine–glycine–aspartate) (cRGD) as ligand for in vivo tumor targeting. The hydrodynamic size of the NPs was determined to be 150–180 nm and the critical micellar concentration (CMC) was estimated to be 10.5 mg l ^{− 1}. Our in vitro study shows that these NPs by themselves had negligible cytotoxicity to human pancreatic cancer (Panc-1) and human glioblastoma (U87) cell lines. Near infrared (NIR) microscopy and flow cytometry demonstrated that the cRGD conjugated PLGA-4-arm-PEG polymeric NPs were taken up more efficiently by U87MG glioma cells, over-expressing the α_vβ₃ integrin, when compared with the non-targeted NPs. Whole body imaging showed that the cRGD conjugated PLGA-4-arm-PEG branched polymeric NPs had the highest accumulation in the pancreatic tumor site of mice at 48 h post-injection. Physical, hematological, and pathological assays indicated low in vivo toxicity of this NP formulation. These studies on the ability of these bioconjugated PLGA-4-arm-PEG polymeric NPs suggest that the prepared polymeric NPs may serve as a promising platform for detection and targeted drug delivery for pancreatic cancer.

We report the novel assembly method of CdSe quantum dot (QD)/pyridine/multi-walled carbon nanotube (CdSe–py–MWNT) hybrid material between electrodes using two-step dielectrophoresis (DEP). At the first step, we assembled the individual MWNT between electrodes by the DEP method. At the second step, the CdSe–py materials were assembled onto the MWNT by DEP method again, which enables site specific and density controlled assembly of QDs. As the photoresponse results, the recovery time of the device fabricated was about 250 times faster than that of a similar CdSe–py–SWNT device using a single-walled carbon nanotube (SWNT) instead of a MWNT. Moreover, it was demonstrated that the optoelectronic property of the device could be modulated by the size of CdSe NQD assembled on a MWNT. We characterized the material and the device by using SEM, TEM, absorption spectroscopy, and optoelectronic instruments.

We study the effects of different nanopore geometries (double-conical, single-conical, cylindrical) on the electrostatic potential distribution and ionic conductivity in a double-layered semiconductor nanopore device as functions of the applied membrane bias. Ionic current–voltage characteristics as well as their rectification ratios are calculated using a simple ion transport model. Based on our calculations, we find that the double-layered semiconductor membrane with a single-conical nanopore with a narrow opening in the n-Si layer exhibits the largest range of available potential variations in the pore and, thus, may be better suited for control of polymer translocation through the nanopore.

Here we investigate high frequency AC transport through narrow graphene nanoribbons with top-gate potentials that form a localized quantum dot. We show that as a consequence of the finite dwell time of an electron inside the quantum dot (QD), the QD behaves like a classical inductor at sufficiently high frequencies  GHz. When the geometric capacitance of the top-gate and the quantum capacitance of the nanoribbon are accounted for, the admittance of the device behaves like a classical serial RLC circuit with resonant frequencies ω ∼ 100–900 GHz and Q-factors greater than 10⁶. These results indicate that graphene nanoribbons can serve as all-electronic ultra-high frequency oscillators and filters, thereby extending the reach of high frequency electronics into new domains.

In this paper, we describe wafer-scale fabrication and characterization of plasmonic chips—containing different sizes and spacings of metallic micro- and nanoline structures—using deep UV lithography. Using a high dose (25 mJ cm ^{− 2}) and a proper lift-off process, feature sizes as small as 25 nm are obtained. Moreover, we study the dependence of surface plasmon resonance on the angle of incidence and wavelength for different micro- and nanoline size and spacing values, yielding localized to quasi-propagative plasmonic behaviors. Rigorous coupled wave analysis (RCWA) techniques are employed to numerically confirm these experimental observations. Finally, the refractive index of media around the SPRI sensor chips is varied, showing the angulo-spectral regions of higher sensitivity for each type of structure.

We show that both the morphology and the optoelectronic properties of SiGe islands growing in the pits of periodically pre-patterned Si(001) substrates are determined by the amount of Ge deposited per unit cell of the pattern. Pit-periods (p) ranging from 300 to 900 nm were investigated, and Ge growth was performed by molecular beam epitaxy (MBE) at temperatures of 690 and 760 °C. The ordered SiGe islands show photoluminescence (PL) emission, which becomes almost completely quenched, once a critical island volume is exceeded. By atomic force and transmission electron microscope images we identify the transition from pyramid-shaped to dome-shaped islands with increasing p. Eventually, the nucleation of dislocations in the islands leads to PL quenching. Below a critical Ge coverage a narrowing and a blue shift of the PL emission is observed, as compared to islands grown on a planar reference area of the same sample.

Orchestrated structure evolution (OSE) is a scalable manufacturing method that combines the advantages of top-down (tool-directed) and bottom-up (self-propagating) approaches. The method consists of a seed patterning step that defines where material nucleates, followed by a growth step that merges seeded islands into the final patterned thin film. We develop a model to predict the completed pattern based on a computationally efficient approximate Green's function solution of the diffusion equation plus a Voronoi diagram based approach that defines the final grain boundary structure. Experimental results rely on electron beam lithography to pattern the seeds, followed by the mass transfer limited growth of copper via electrodeposition. The seed growth model is compared with experimental results to quantify nearest neighbor seed-to-seed interactions as well as how seeds interact with the pattern boundary to impact the local growth rate. Seed-to-seed and seed-to-pattern interactions are shown to result in overgrowth of seeds on edges and corners of the shape, where seeds have fewer neighbors. We explore how local changes to the seed location can be used to improve the patterning quality without increasing the manufacturing cost. OSE is shown to enable a unique set of trade-offs between the cost, time, and quality of thin film patterning.

Nanochannels of the order of 20 nm in diameter and forming arrangements that were a few micrometres wide were fabricated on nanometre-thick ice-like deposits on planar mica surfaces at room temperature. Because an atomic force microscopy tip can write lines on ice-like layers covering mica substrates in air that are stable under invariant conditions of humidity and temperature, the water films were modulated with nanochannels. By analysing the shape and morphology of the material removed after channel fabrication for various time intervals, the channel profile was shown to vary with a scale of a tenth of a second. In this configuration (hydrophobic tip and hydrophilic substrate, 65% RH), at the channel top region there were only aggregates of loose flakes formed after the film inscription but no liquid. Apparently, the Kelvin effect is responsible for the nanochannel profile variation with time, but the calculated and measured values of the drainage time constant are at variance by six orders of magnitude. This reduction of the mass transfer is associated with the small dimensions of the ∼ 10 nm-wide channels.

The rapid and sensitive detection of DNA has recently attracted worldwide attention for a variety of disease diagnoses and detection of harmful bacteria in food and drink. In this paper, we carried out a comparative study based on surface plasmon resonance enhanced ellipsometry (SPREE) for the detection of oligodeoxynucleotides (ODNs) using micro- and nano-array platforms. The micro-arrayed surfaces were fabricated by a photolithography approach using different types of mask having varying size and shape. Well-ordered arrays of high aspect ratio polymeric nanotubes were also obtained using high molecular weight polystyrene (PS) and anodic aluminum oxide (AAO) membranes having 200 nm pore diameters. The SPREE sensors were then prepared by direct coupling of thiolated probe-ODNs, which contain suitable spacer arms, on gold-coated micro- and nano-arrayed surfaces. We experimentally demonstrated that, for the first time, gold-coated free standing polymeric nano-arrayed platforms can easily be produced and lead to a significant sensor sensitivity gain compared to that of the conventional SPREE surfaces of about four times. We believe that such an enhancement in sensor response could be useful for next generation sensor systems.

The fabrication and characterization of single-walled carbon nanotube (SWCNT) composite thin film micropatterns and suspended beams prepared by lithography-compatible layer-by-layer (LbL) nano-self-assembly are demonstrated. Negatively charged SWCNTs are assembled with a positively charged polydiallyldimethylammonium chloride, and the composite thin film is patterned by oxygen plasma etching with a masking layer of photoresist, resulting in a feature size of 2 µm. Furthermore, the SWCNT nanocomposite stripe pattern with a metal clamp on both ends is released by etching a sacrificial layer of silicon dioxide in the hydrofluoric acid vapor. I–V measurement reveals that the resistance of SWCNT nanocomposite film decreases by 23% upon release, presumably due to the effect of reorientation of CNTs caused by the deflection of about 50 nm. A high Young's modulus is found in a range of 500–800 GPa based on the characterization of a fixed–fixed beam using nanoindentation. This value is much higher than those of the other CNT–polymer composites reported due to organization of structures by self-assembly and higher loading of CNTs. The stiff CNT–polymer composite thin film micropattern and suspended beam have potential applications to novel physical sensors, nanoelectromechanical switches, other M/NEMS devices, etc.

Atomic layer deposition (ALD) was used to synthesize graphene-based metal oxide nanocomposites. This strategy was fulfilled on the preparation of TiO₂–graphene nanosheet (TiO₂–GNS) nanocomposites using titanium isopropoxide and water as precursors. The synthesized nanocomposites demonstrated that ALD exhibited many benefits in a controllable means. It was found that the as-deposited TiO₂ was tunable not only in its morphologies but also in its structural phases. As for the former, TiO₂ was transferable from nanoparticles to nanofilms with increased cycles. With regard to the latter, TiO₂ was changeable from amorphous to crystalline phase, and even a mixture of the two with increased growth temperatures (up to 250 °C). The underlying growth mechanisms were discussed and the resultant TiO₂–GNS nanocomposites have great potentials for many applications, such as photocatalysis, lithium-ion batteries, fuel cells, and sensors.

Carbon is a commonly used p-type dopant in planar III–V semiconductors, however its use in nanowire (NW) growth has been much less reported. In this work we show that the morphology of gold assisted GaAs NWs can be strongly modified by the presence of CBr₄ vapor during growth by metalorganic vapor phase epitaxy. GaAs NWs were grown under conditions which result in strong tapering and lateral growth at low growth temperatures by the use of triethylgallium (TEGa) instead of the more usual precursor, trimethylgallium (TMGa). Under these conditions, NWs grown in the presence of CBr₄ exhibit higher axial and lower radial growth rates, and negligible tapering compared with NWs grown in the absence of CBr₄ under the same conditions. We attribute this primarily to the suppression of the 2d growth rate by CBr₄, which enhances the axial growth rate of the nanowires. NWs grown with CBr₄ show stacking-fault-free zincblende structure, while the NWs grown without CBr₄ show a high density of stacking faults. This work underlines the striking effects which precursor chemistry can have on nanowire morphology.

A catalyst-free and highly efficient synthetic method for growing carbon nano-onions (CNOs) in open air has been developed through the laser resonant excitation of a precursor molecule, ethylene, in a combustion process. Highly concentric CNO particles with improved crystallinity were obtained at a laser wavelength of 10.532 µm through the resonant excitation of the CH₂ wagging mode of the ethylene molecules. A higher growth rate up to 2.1 g h ^{− 1} was obtained, compared with that without a laser (1.3 g h ^{− 1}). Formation of the CNOs with ordered graphitic shells is ascribed to the decomposition of polycyclic aromatic hydrocarbons (PAHs) into C₂ species. The optical limiting performances of the CNOs grown by the combustion processes were investigated. CNOs grown at 10.532 µm laser excitation demonstrated improved optical limiting properties due to the improved crystallinity.

Increasing interest in graphene research in basic sciences and applications emphasizes the need for an economical means of synthesizing it. We report a method for the synthesis of graphene on commercially available stainless steel foils using direct thermal chemical vapor deposition. Our method of synthesis and the use of relatively cheap precursors such as ethanol (CH₃CH₂OH) as a source of carbon and SS 304 as the substrate proved to be economically viable. The presence of single- and few-layer graphene was confirmed using confocal Raman microscopy/spectroscopy. X-ray photoelectron spectroscopic measurements were further used to establish the influence of various elemental species present in stainless steel on graphene growth. The role of cooling rate on surface migration of certain chemical species (oxides of Fe, Cr and Mn) that promote or hinder the growth of graphene is probed. Such analysis of the chemical species present on the surface can be promising for graphene based catalytic research.

This study investigated the mechanical properties of vibrating cantilevered multiwall carbon nanotubes in terms of energy loss in a vibrating nanotube. Young's moduli of the nanotubes show a clear dependence of the perfection of the sp² carbon network, as determined from Raman spectroscopy. The energy loss corresponding to the inverse of the quality factor increases with increasing tube diameter, although the nanotube maintains high mechanical strength around 0.5 TPa. This fact implies that the vibration energy is dissipated mainly not by defects, but by van der Waals interactions between walls.

Particle–polymer nanocomposites often exhibit mechanical properties described poorly by micromechanical models that include only the particle and matrix phases. Existence of an interfacial region between the particle and matrix, or interphase, has been posited and indirectly demonstrated to account for this effect. Here, we present a straightforward analytical approach to estimate effective elastic properties of composites comprising particles encapsulated by an interphase of finite thickness and distinct elastic properties. This explicit solution can treat nanocomposites that comprise either physically isolated nanoparticles or agglomerates of such nanoparticles; the same framework can also treat physically isolated nanoparticle aggregates or agglomerates of such aggregates. We find that the predicted elastic moduli agree with experiments for three types of particle–polymer nanocomposites, and that the predicted interphase thickness and stiffness of carbon black–rubber nanocomposites are consistent with measured values. Finally, we discuss the relative influence of the particle–polymer interphase thickness and stiffness to identify maximum possible changes in the macroscale elastic properties of such materials.

Excellent photoconductive properties have been found in Sb₂O₃ nanobelts synthesized by a surfactant-assisted solvothermal method. Visible-light photodetectors have been designed from Sb₂O₃ nanobelt networks using micrometer-wide gold wires as masks. Photodetectors show high sensitivity to visible light, high stability, and reproducibility. Fast response and decay times (<0.3 s) are comparable or even better than these parameters in many other metal oxide nanoscale photodetectors. The dominant mechanism of excellent photoconductivity is attributed to the barrier height modulations in the nanobelt-to-nanobelt contact regions. These results demonstrate that Sb₂O₃ nanobelt networks can indeed serve as high-performance photodetectors in the visible light range.

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