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Chiral nanostructures exhibit strong coupling to the spin angular momentum of incident photons. The integration of metal nanostructures with semiconductor nanoparticles (NPs) to form hybrid plasmon-exciton nanoscale assemblies can potentially lead to plasmon-induced optical activity and unusual chiroptical properties of plasmon-exciton states. Here we investigate such effects in supraparticles (SPs) spontaneously formed from gold nanorods (NRs) and chiral CdTe NPs. The geometry of this new type of self-limited nanoscale superstructures depends on the molar ratio between NRs and NPs. NR dimers surrounded by CdTe NPs were obtained for the ratio NR/NP = 1:15, whereas increasing the NP content to a ratio of NR/NP = 1:180 leads to single NRs in a shell of NPs. The SPs based on NR dimers exhibit strong optical rotatory activity associated in large part with their twisted scissor-like geometry. The preference for a specific nanoscale enantiomer is attributed to the chiral interactions between CdTe NP in the shell. The SPs based on single NRs also yield surprising chiroptical activity at the frequency of the longitudinal mode of NRs. Numerical simulations reveal that the origin of this chiroptical band is the cross talk between the longitudinal and the transverse plasmon modes, which makes both of them coupled with the NP excitonic state. The chiral SP NR-NP assemblies combine the optical properties of excitons and plasmons that are essential for chiral sensing, chiroptical memory, and chiral catalysis.

DNA-bridged pairs of seemingly spherical metallic nanoparticles (NPs) have chiral geometry due to the nonideal oblong shape of the particles and scissor-like conformation. Here we demonstrate that deposition of gold and silver shells around the NP heterodimers enables spectral modulation of their chiroplasmonic bands in 400-600 nm region and results in significantly enhanced optical activity with g-factors reaching 1.21 × 10(-2). The multimetal heterodimers optimized for coupling with the spin angular momentum of incident photons enable polymerase chain reaction (PCR)-based DNA detection at the zeptomolar level. This significant improvement in the sensitivity of detection is attributed to improvement of base pairing in the presence of NPs, low background for chiroplasmonic detection protocol, and enhancement of photon-plasmon coupling for light with helicity matching that of the twisted geometry of the heterodimers.

Chirality of plasmonic films can be strongly enhanced by three-dimensional (3D) out-of-plane geometries. The complexity of lithographic methods currently used to produce such structures and other methods utilizing chiral templates impose limitations on spectral windows of chiroptical effects, the size of substrates, and hence, further research on chiral plasmonics. Here we demonstrate 3D chiral plasmonic nanostructures (CPNs) with high optical activity in the visible spectral range based on initially achiral nanopillars from ZnO. We made asymmetric gold nanoshells on the nanopillars by vacuum evaporation at different inclination and rotation angles to achieve controlled symmetry breaking and obtained both left- and right-rotating isomers. The attribution of chiral optical effects to monolithic enantiomers made in this process was confirmed by theoretical calculations based on their geometry established from scanning electron microscope (SEM) images. The chirality of the nanoshells is retained upon the release from the substrate into a stable dispersion. Deviation of the incident angle of light from normal results in increase of polarization rotation and chiral g-factor as high as -0.3. This general approach for preparation of abiological nanoscale chiral materials can be extended to other out-of plane 3D nanostructures. The large area films made on achiral nanopillars are convenient for sensors, optical devices, and catalysis.

Treatments of neurological diseases, diagnostics of brain malfunctions, and the realization of brain-computer interfaces require ultrasmall electrodes that are "invisible" to resident immune cells. Functional electrodes smaller than 50 μm are impossible to produce with traditional materials due to high interfacial impedance at the characteristic frequency of neural activity and insufficient charge storage capacity. The problem can be resolved by using gold nanoparticle nanocomposites. Careful comparison indicates that layer-by-layer assembled films from Au NPs provide more than 3-fold improvement in interfacial impedance and 1 order of magnitude increase in charge storage capacity. Prototypes of microelectrodes could be made using traditional photolithography. Integration of unique nanocomposite materials with microfabrication techniques opens the door for practical realization of the ultrasmall implantable electrodes. Further improvement of electrical properties is expected when using special shapes of gold nanoparticles.

Development of multifunctional drug delivery vehicles with therapeutic and imaging capabilities as well as in situ methods of monitoring of intracellular processes will greatly benefit from a simple method of preparation of plasmonic Au structures with nanometer scale gaps between sharp metallic elements where the so-called SERS hot spots can be formed. Here the synthesis of gold lace capsules with average diameters ca. 100 nm made of a network of metallic branches 3-5 nm wide and separated by 1-3 nm gaps is reported. Biocompatible amphiphilic polyurethanes (PUs) were used as template for these particles. The unusual topology of the produced gold lace shells somewhat reminiscent of Fabergé eggs is likely to reflect the network of hydrophobic and hydrophilic domains of PU globules. The gold lace develops from initial open weblike structures by gradual enveloping the PU template. The diameter of gold lace shell is determined by the size of PUs in water and can be adjusted by the molecular mass of PUs. The close proximity between branches makes them excellent supports for surface-enhanced Raman spectroscopy (SERS), which was demonstrated using 1-naphthalenethiol upon excitation with photons with different wavelengths. The loading and releasing of pyrene as a model of hydrophobic drugs and the use of SERS to monitor it were demonstrated.

The safety, function, and longevity of implantable neuroprosthetic and cardiostimulating electrodes depend heavily on the electrical properties of the electrode-tissue interface, which in many cases requires substantial improvement. While different variations of carbon nanotube materials have been shown to be suitable for neural excitation, it is critical to evaluate them versus other materials used for bioelectrical interfacing, which have not been done in any study performed so far despite strong interest to this area. In this study, we carried out this evaluation and found that composite multiwalled carbon nanotube-polyelectrolyte (MWNT-PE) multilayer electrodes substantially outperform in one way or the other state-of-the-art neural interface materials available today, namely activated electrochemically deposited iridium oxide (IrOx) and poly(3,4-ethylenedioxythiophene) (PEDOT). Our findings provide the concrete experimental proof to the much discussed possibility that carbon nanotube composites can serve as excellent new material for neural interfacing with a strong possibility to lead to a new generation of implantable electrodes.

The idea of electronic yarns and textiles has appeared for quite some time, but their properties often do not meet practical expectations. In addition to chemicallmechanical durability and high electrical conductivity, important materials qualifications include weavablity, wearability, light weight, and "smart" functionalities. Here we demonstrate a simple process of transforming general commodity cotton threads into intelligent e-textiles using a polyelectrolyte-based coating with carbon nanotubes (CNTs). Efficient charge transport through the network of nanotubes (20 omega/cm) and the possibility to engineer tunneling junctions make them promising materials for many high-knowledge-content garments. Along with integrated humidity sensing, we demonstrate that CNT-cotton threads can be used to detect albumin, the key protein of blood, with high sensitivity and selectivity. Notwithstanding future challenges, these proof-of-concept demonstrations provide a direct pathway for the application of these materials as wearable biomonitoring and telemedicine sensors, which are simple, sensitive, selective, and versatile.

The excitation of surface plasmons in individual silver nanowires and gold nanorods is investigated by means of high-resolution electron energy loss spectroscopy in a transmission electron microscope. The transverse and longitudinal modes of these nanostructures are resolved, and the size variation of the plasmon peaks is studied. The effect of electromagnetic coupling between closely spaced nanoparticles is also observed. Finally, the relation between energy-loss measurements and optical spectroscopy of nanoparticle plasmon modes is discussed.

Molecular engineering of multilayered composites by layer-by-layer assembly (LBL) made possible easy replication of mechanical properties of nacre. Taking advantage of the ability of LBL to finely control the structure of the composite, one can further improve the mechanical properties of the multilayers, e.g., increase the strength and stiffness, and gain better understanding of the nanoscale and molecular scale mechanics of the materials critical for a variety of advanced technologies. In this study, we have replaced poly(diallyldimethylammonium chloride) (PDDA) (sigmaUTS approximately 12 MPa, E approximately 0.2 GPa) with a much stronger polysaccharide polycation, chitosan (CH, sigmaUTS approximately 108 MPa, E approximately 2 GPa), considering that its superior molecular strength will improve the macroscale mechanical properties of the nanocomposite: strength and stiffness. Free-standing films of the CH and montmorillonite (MTM) have been successfully made, and the resulting films revealed high uniformity with very high loading of MTM closely comparable to that in the natural nacre, approximately 80 wt %. Contrary to our expectations and theoretical predictions, the CH-MTM composite revealed lower strength and stiffness than those of PDDA-MTM and lower strength than CH polymer itself: sigmaUTS approximately 80 MPa and E approximately 6 GPa. Analysis of the morphology of adsorbing CH chains with atomic force microscopy revealed highly elongated molecules, which is opposite to the observations made for PDDA. Plane-to-plane adhesion showed a factor of approximately 4 lower strength when compared to PDDA-MTM nanocomposite. Altogether these facts support the conclusion that CH lacks flexibility necessary for strong adhesion and efficient load transfer between the organic matrix and MTM platelets. High rigidity of the CH chains does not allow them to acquire a conformation necessary for maximizing the interfacial attraction with nanoscale component of the composite. These observations create an important foundation in the experimental design of the high-performance nanocomposite materials.

We describe the physical properties of excitons in hybrid complexes composed of semiconductor and metal nanoparticles. The interaction between individual nanoparticles is revealed as an enhancement or suppression of emission. Enhanced emission comes from electric field amplified by the plasmon resonance, whereas emission suppression is a result of energy transfer from semiconductor to metal nanoparticles. The emission intensity and energy transfer rate depend strongly on the geometrical parameters of the superstructure and the physical and material properties of the nanoparticles. In particular, the emission enhancement effect appears for nanoparticles with relatively small quantum yield, and silver nanoparticles have stronger enhancement compared to gold ones. Using realistic models, we review and analyze available experimental data on energy transfer between nanoparticles. In hybrid superstructures conjugated with polymer linkers, optical emission is sensitive to environmental parameters such as, for example, temperature. This sensitivity comes from expansion or contraction of a linker. With increasing temperature, emission of polymer-conjugated complexes can decrease or increase depending on the organization of a superstructure. The structures described here have potential as sensors and actuators.

Nanoparticle/nanowire assemblies with a degree of radial organization were prepared around luminescent semiconducting CdTe nanowires using bioconjugation with streptavidin and D-biotin linkers. Red-emitting nanowires (6.62 +/- 1.55 nm diameter, 512 +/- 119 nm length) and green-emitting nanoparticles (3.2 +/- 0.7 nm diameter) were surface-modified with biotin, while orange-emitting nanoparticles (4.1 +/- 1.2 nm diameter) were decorated with streptavidin. CdTe nanocrystals produced two fuzzy layers around the nanowires in which the diameter of CdTe nanoparticles decreased with the distance from the nanowire axis. Förster resonance energy transfer (FRET) from the outside layer of nanoparticles to the central nanowire was observed for nanowires conjugated with 4.1 nm CdTe. Addition of 3.2 nm CdTe resulted in a red-orange-green optical progression with band gaps of CdTe decreasing toward the axis of the superstructure. In this case, 4-fold luminescence enhancement of the nanowire luminescence was observed and was attributed to multistep FRET. This observation indicated the accumulation of photogenerated excitons in the cascade terminal. A simple model of multiconjugated superstructure with cascade energy transfer is developed and used to describe and understand the experimental data. The experimental data and theoretical model suggest the possibility of utilization of the prepared superstructures with radial symmetry in several classes of optoelectronic devices including nanomaterials for energy collection. They can also be a convenient model object for the investigation of methods of energy funneling in nanoscale assemblies.

Nanoscale superstructures made from CdTe nanowires (NWs) and metal nanoparticles (NPs) are prepared via bioconjugation reactions. Prototypical biomolecules, such as d-biotin and streptavidin pair, were utilized to connect NPs and NWs in solution. It was found that Au NPs form a dense shell around a CdTe NW. The superstructure demonstrated unusual optical effects related to the long-distance interaction of the semiconductor and noble metal nanocolloids. The NW−NP complex showed 5-fold enhancement of luminescence intensity and a blue shift of the emission peak as compared to unconjugated NW. The system was theoretically examined in a simple model of CdTe NW coaxially surrounded by an Au shell, which gives excellent agreement with experimental data. The combination of time-resolved luminescence and calculations demonstrated that increase of fluorescence intensity occurs due to stimulation of photon emission by an electromagnetic field generated around the Au NP. The process is reminiscent of SERS, although d...

We report formation of polyelectrolyte/multiwall carbon nanotube (MWNT) multilayers by the layer-by-layer assembly technique. Both “hollow” and “bamboo” type MWNTs were employed. Scanning electron and atomic force microscopy indicate high structural homogeneity of the prepared composites. Ellipsometry and the absorbance spectroscopy confirm sequential adsorption of oppositely charged nanotubes and the polyelectrolyte resulting in uniform growth of the polyelectrolyte/MWNT films. Measurements of the mechanical properties show that these are strong composite hybrid films with mechanical properties exceeding many carbon nanotube composites made by mixing, or in-situ polymerization. Bamboo-type carbon nanotube composites display ultimate tensile strength of 150 ± 35 MPa and Young modulus of 4.5 ± −0.8 GPa as compared to 110 ± 25 MPa and 2 ± 0.5 GPa in composites made from common hollow MWNTs. This indicates that the morphology of the fibers can substantially improve matrix connectivity on the material mitigat...

Variation of band gap across the nanowire length would be an exceptionally attractive property for the fabrication of on-nanowire devices such as resonance tunneling diodes (RTD). Band gap variation can be achieved by selective thinning of semiconductor wires by scanning probe lithography (SPL) technique. The external bias applied to a conductive AFM tip during scanning of CdTe nanowires was chosen so as to exceed the threshold of electric field-assisted evaporation of CdTe, estimated to be 5.5 V. Relatively high external voltages of 10−11 V cause fast and complete disintegration of a nanowire portion under the tip. In this way the nanowire can be cut to a desired length. Selection of a voltage between 5.5 and 10 V allows one to control the speed of CdTe evaporation. Thus, one can modulate the thickness of the semiconductor with angstrom scale precision along the nanowire length. Smaller diameter of the nanowire results in increase of quantum confinement in selected areas. The double barrier quantum well ...

CdTe nanowires with bristled SiO2 coatings resembling nanoscale centipedes were produced in a modified Stober process when mercaptosuccinic acid was used as a stabilizer. The reason for the unusual morphology of the coating is believed to be the nonuniform distribution of the stabilizers on the surface of the nanowire. Atomistic calculations of CdTe nanoparticles as a simplified model of a nanowire surface reveal that phase separation of the mercaptosuccinic acid and (3-mercaptopropyl)trimethoxysilane is an energetically favorable process. These data indicate that the heterogeneity of the nanocolloid surface is an important property that may be taken advantage of for preparation of nanostructures of high complexity. From a practical perspective, the centipede nanowires can be a uniquely useful material for high-strength nanoscale composites.

Nanostructured thin films fabricated from semiconductor nanoparticles (NPs) are of great interest for biomedical applications, but NP materials based on heavy metals can be cytotoxic. In this work, the preparation of semiconductor NPs followed the protocol of layer-by-layer (LBL) assembly, which alleviates this problem. Collagen/poly(acrylic acid) bilayers were added to CdTe/polycation LBL films to produce porous collagen bilayers. Such stratified multilayer systems showed successful cell attachment and survival while native NP films were strongly cytotoxic.

Layer-by-layer sequential adsorption technique (LBL) can be utilized as a deposition method for nanostructured coatings on highly curved micrometer to millimeter scale surfaces, which is demonstrated in this work on a model films of strongly luminescent CdTe nanoparticles. Unlike LBL on colloids and flat surfaces, such procedure opens the door for the preparation of conformal nanostructured coatings for a variety of photonics and lab-on-the chip devices with predictable technological importance. Confocal microscopy data showed that prepared CdTe/PDDA coatings were found to be uniform and continuous. Strong coupling of the nanoparticle luminescence into the optical fiber attributed to high refractive index of CdTe/PDDA composite was obtained. As applied to nanoparticle coatings, two unanticipated effects were observed: (1) gradual red shift of the luminescence spectrum as the layer thickness increases; (2) two-stage luminescence transient including the significant enhancement of the luminescence during fi...

Complementary bioconjugates based on antibody−antigen interactions were synthesized from luminescent CdTe nanoparticles (NPs). Antigen (bovine serum albumin) was conjugated to red-emitting CdTe NPs, while green-emitting NPs were attached to the corresponding anti-BSA antibody (IgG). The NP bioconjugates were characterized by native and SDS−PAGE electrophoresis, gel-permeation HPLC, and circular dichroism. Antigen−antibody binding affinity was evaluated by enzyme-linked immunosorbent assay (ELISA). The formation of BSA−IgG immunocomplex resulted in the Forster resonance energy transfer (FRET) between the two different NPs: the luminescence of green-emitting NPs was quenched whereas the emission of the red-emitting NPs was enhanced. The luminescence recovered when the immunocomplex was exposed to an unlabeled antigen. The immunocomplexes can be considered as a prototype of NP superstructures based on biospecific ligands, while the competitive FRET inhibition can be used in an immunoassay protocol.

Layer-by-layer (LBL) films of a fulleropyrrolidinium−androstane−ferrocene dyad revealed a surprisingly high level of intermolecular organization. In particular, in every adsorption layer, the films self-assemble into linear nanowire superstructures. Given the inherent intramolecular charge transfer performance of the dyads, such a film organization facilitates the charge diffusion from the photoactive centers to the electrodes, due to extensive interpenetration of the layers, which leads to multiple contacts between the fullerene−ferrocene nanowires.

Conjugates of bovine serum albumin and CdTe nanoparticles capped with l-cysteine have been synthesized via a one-pot glutaric dialdehyde cross-linking procedure. Diads (1:1) with some amount of 2:1 albumin−nanoparticle assemblies preferably form in this reaction, as evidenced by gel electrophoresis. Circular dichroism spectroscopy demonstrates that the tertiary structure of the protein remains largely intact after the conjugation. Attachment of protein moieties result in a significant increase of CdTe emission, which is attributed to the resonance energy transfer from the tryptophan moieties of albumin to CdTe nanoparticles acting as receptors for the protein antennae.

Safety of water was for a long time and still is one of the most pressing needs for many countries and different communities. Despite the fact that there are potentially many methods to evaluate water safety, finding a simple, rapid, versatile, and inexpensive method for detection of toxins in everyday items is still a great challenge. In this study, we extend the concept of composites obtained impregnation of porous fibrous materials, such as fabrics and papers, by single walled carbon-nanotubes (SWNTs) toward very simple but high-performance biosensors. They utilize the strong dependence of electrical conductivity through nanotubes percolation network on the width of nanotubes-nanotube tunneling gap and can potentially satisfy all the requirements outlined above for the routine toxin monitoring. An antibody to the microcystin-LR (MC-LR), one of the common culprits in mass poisonings, was dispersed together with SWNTs. This dispersion was used to dip-coat the paper rendering it conductive. The change in conductivity of the paper was used to sense the MC-LR in the water rapidly and accurately. The method has the linear detection range up to 10 nmol/L and non-linear detection up to 40 nmol/L. The limit of detection was found to be 0.6 nmol/L (0.6 ng/mL), which satisfies the strictest World Health Organization standard for MC-LR content in drinking water (1 ng/mL), and is comparable to the detection limit of traditional ELISA method of MC-LR detection, while drastically reducing the time of analysis by more than an order of magnitude, which is one of the major hurdles in practical applications. Similar technology of sensor preparation can also be used for a variety of other rapid environmental sensors.

X-ray based computed tomography (CT), is among the most convenient imaging/diagnostic tools in hospitals today in terms of availability, efficiency and cost. However, in contrast to magnetic resonance imaging (MRI) and various nuclear medicine imaging modalities, CT is not considered a molecular imaging modality since targeted and molecularly specific contrast agents have not yet been developed. Here we describe a targeted molecular imaging platform that enables, for the first time, cancer detection at the cellular and molecular level with standard clinical CT. The method is based on gold nano-probes that selectively and sensitively target tumor selective antigens, while inducing distinct contrast in CT imaging (increased x-ray attenuation). We present an in vitro proof of principle demonstration for head and neck cancer, showing that the attenuation coefficient for the molecularly targeted cells is over 5 times higher than for identical but untargeted cancer cells or for normal cells. We expect this novel imaging tool to lead to significant improvements in cancer therapy, due to earlier detection, accurate staging and micro-tumor identification.

Polymerase chain reaction (PCR) was realized on the surface of gold nanoparticles (NPs) as a tool for self-organization at nanoscale and as a step toward programmable production of sufficient quantities of functional metallic superstructures. The assembly is controlled by varying the density of the primer on the surface of gold NPs and the number of PCR cycles generating a mixture of dimers, trimers, tetramers, etc., with gradually increasing complexity. This process leads to strong chirality of the assemblies arising from the three-dimensional positioning of NPs in space which had never been observed before. A circular dichroism band of the superstructures coincides with the plasmon oscillations of the multi-NP systems of Au colloids. This new collective optical property of NPs embracing the diversity of shapes and diameters in the starting dispersions opens unique opportunities for the development of negative index materials.

One of the key challenges to engineering neural interfaces is to minimize their immune response toward implanted electrodes. One potential approach is to manufacture materials that bear greater structural resemblance to living tissues and by utilizing neural stem cells. The unique electrical and mechanical properties of carbon nanotubes make them excellent candidates for neural interfaces, but their adoption hinges on finding approaches for "humanizing" their composites. Here we demonstrated the fabrication of layer-by-layer assembled composites from single-walled carbon nanotubes (SWNTs) and laminin, which is an essential part of human extracellular matrix. Laminin-SWNT thin films were found to be conducive to neural stem cells (NSC) differentiation and suitable for their successful excitation. We observed extensive formation of functional neural network as indicated by the presence of synaptic connections. Calcium imaging of the NSCs revealed generation of action potentials upon the application of a lateral current through the SWNT substrate. These results indicate that the protein-SWNT composite can serve as materials foundation of neural electrodes with chemical structure better adapted with long-term integration with the neural tissue.

Layer-by-layer (LBL) assembly is one of the most ubiquitous coating techniques today. It also offers a pathway for multifunctional/multicomponent materials with molecular-scale control of stratified structures. However, technological applications of LBL are impeded by laborious and fluid-demanding nature of the process. While vertical organization of LBL films is natural for this technique, the control of lateral organization of the films is fairly difficult. Using the deposition of carbon nanotubes (SWNTs) and other nanoscale colloids, we introduce here a new approach to LBL based on dewetting phenomena, d-LBL. Its strengths include: (1) elimination of rinsing steps, (2) significant acceleration of the process, (3) improvement of lateral organization of LBL films, and (4) ability to produce nanostructured coatings from colloids when classical LBL fails. The generality of d-LBL can compete with traditional LBL and is demonstrated for cellulose nanowires, polyelectrolyte pairs, and semiconductor nanoparticles, metal oxides, and Au nanorods.

The development of a contrast agent for a laser optoacoustic imaging system (LOIS) can significantly widen preclinical and clinical applications of this imaging modality for early detection of cancerous tumors. Gold nanorods were engineered to enhance the contrast for optoacoustic imaging. Under in vivo conditions, 25 microL of gold nanorods solution at a concentration of 1.25 pM were injected into nude mice and detected using a single-channel acoustic transducer. LOIS was used to visualize the distribution of gold nanoparticles at a concentration of 125 pM in vivo when 100 microL of solution of gold nanoparticles was delivered subcutaneously. Our results suggest that LOIS can be used for in vivo detection of gold nanorods at low concentrations and the nanoparticles can be engineered to enhance the diagnostic power of optoacoustic imaging.

Recent experiments have reported the self-assembly of TGA- and DMAET-stabilized CdTe nanoparticles (NPs) into wires and sheets, respectively, depending upon the stabilizer used. We develop a mesoscale model based on quantum mechanical calculations and perform Monte Carlo simulations of these NPs to elucidate the conditions under which these two structures will form. We show that consideration of NP shape, directional attraction, and electrostatic interactions is key to determining the anisotropy of the NP-NP interaction and final self-assembled structures.

The same properties that made carbon nanotube (CNT) composites interesting for electronics, sensing, and ultrastrong structural materials also make them an asset for biomedical engineering. The combination of electron conductivity, corrosion resistance, and strength are essential for neuroprosthetic devices. All of the studies in this area demonstrating cellular adhesion and signal transduction activity on CNT matrixes were conducted, so far, with terminally differentiated primary cells and cancerous cell lines. Neural stem cells are very plastic neural precursors capable of adapting to environmental conditions and recreating signal transduction pathways. Their intrinsic biological functionality not only makes the transition to stem cell cultures a difficult-to-avoid step but also implies several fundamentally important challenges. Here we demonstrate that mouse embryonic neural stem cells (NSCs) from the cortex can be successfully differentiated to neurons, astrocytes, and oligodendrocytes with clear formation of neurites on layer-by-layer (LBL) assembled single-walled carbon nanotube (SWNT)-polyelectrolyte multilayer thin films. Biocompatibility, neurite outgrowth, and expression of neural markers were similar to those differentiated on poly-L-ornithine (PLO), one of the most widely used growth substratums for neural stem cells.

The remarkable optical and electrical properties of nanostructured materials are considered now as a source for a variety of biomaterials, biosensing, and cell interface applications. In this study, we report the first example of hybrid bionanodevice where absorption of light by thin films of quantum confined semiconductor nanoparticles of HgTe produced by the layer-by-layer assembly stimulate adherent neural cells via a sequence of photochemical and charge-transfer reactions. We also demonstrate an example of nanoscale engineering of the material driven by biological functionalities.

CdTe nanowires made by self-organization of CdTe nanoparticles in aqueous media were separately conjugated with complementary biological connectors, such as antigen-antibody and biotin-streptavidin. Transmission electron microscopy images and Forster resonance energy transfer measurements in nanowire superstructures with different diameters indicate that biological affinity of the attached proteins results in the formation of crossbar and end-to-side connections between the nanowires. A prototype of a logical circuit made from a triangular arrangement of the nanowires spontaneously assembled on a Si substrate was examined by conducting atomic force microscopy. While diode-like behavior was observed in the sides of the triangle, the nanowire junction points were found to be nonconductive. It was attributed to high tunneling barrier created by protein molecules wedged between the nanowires. Suggestions are made how to reduce it or use the insulating gap between the nanowires as a framework for single-electron devices.