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A noncovalent interaction based self-assembled ruthenium (II) phthalocyanine (RuPc) and N-pyridyl-peryleneimide (PyPMI) dyad has been exploited to fabricate n-type dye-sensitized solar cells (DSSCs). This supramolecular dyad design is an alternative method to replace the most challenging synthesis of covalent-linked dyads. Metal-coordinated-based dyad complex improved the light-harvesting properties of the photoanodes as opposed to when individual dye anchored on TiO2 surface alone. DSSCs comprise of RuPc⋅PyPMI dyad convert light-to-electrical energy more efficiently (η = 2.29%) than those made of single dye under one sun irradiation (100 mW cm−2) condition. The enhanced photovoltaic performance of the dyad-based devices is due to the broader light absorption of the dyad in the longer wavelengths, enabling better electron injection into the conduction band of TiO2. The combined effect of efficient electron-hole charge separation and the long-lived charge-separated states facilitated the higher short-circuit current density (Jsc) and open-circuit voltage (Voc) of the devices. The enhancement of Voc and Jsc of the devices is confirmed by measuring current–voltage (I–V) curve and incident photon to current conversion efficiency (IPCE) spectrum of each device.

Pure anatase titania (TiO2) nanoparticles were anchored on the surface of functionalized multi-walled carbon nanotubes (MWCNTs) using a solution-based synthetic method at room temperature. X-ray diffraction and Raman patterns were used to analyze the structural and phase composition of these nanocomposites, highlighting the formation of anatase TiO2 nanoparticles with MWCNTs up to 0.5 wt.%. The non-spherical particles of TiO2 in the order of 7–12 nm, were confirmed through transmission electron microscopy analysis and these particles were well dispersed on the MWCNTs. The optical absorption spectra of these structures were studied by diffuse reflectance UV–visible spectroscopy. The optical energy band gap of the various nanocomposites was observed from 3.2 to 2.6 eV with an increasing amount of MWCNTs, up to 0.5 wt.%. The generation of OH species in nanocomposites in the presence of visible light irradiation was investigated by photoluminescence spectroscopy. Photoelectrochemical cell performance of TiO2-MWCNTs for 0.5 wt.% content of MWCNTs under light intensity 100 mW/cm2 showed a significant improvement of short-circuit current density from 1.23 to 12.1 mA/cm2 and a cell efficiency (0.090–3.46%) that is better than many reported anatase-based compositions without sensitizer.

This work focuses on the incorporation of fullerenol nanoparticles to get PVA-fullerenol mixed matrix membranes for alcohol dehydration by pervaporation. Cross-linked hybrid membranes based on composites of polyvinyl alcohol (PVA) and low-hydroxylated fullerenol C60(OH)12 have been prepared by two different procedures. To improve the dispersion of the functionalized fullerene in the PVA network, the hydrodynamic properties of PVA, fullerenol and PVA/fullerenol composites in dilute solutions were studied by viscometry and dynamic light scattering. It was shown that the aggregate sizes increased with the increase of fullerenol content in the PVA/fullerenol composite solutions. The effect of low-hydroxylated fullerenol on the structure and morphology of PVA membranes was investigated by small-angle X-ray scattering and atomic force microscopy. It was observed that the incorporation of 5 wt.% fullerenol and cross-linking with maleic acid led to a more uniform distribution of the amorphous PVA phase. As a result, membrane transport characteristics were improved for the dehydration of n-butanol–water mixtures by pervaporation. The PVA membranes containing 35 wt.% maleic acid and 5 wt.% fullerenol exhibited the best transport properties. Keywords: Polyvinyl alcohol, Fullerenol, Composite, n-Butanol, Pervaporation

Hybrid membranes based on composites of polyvinyl alcohol (PVA) and low-hydroxylated fullerenol C 60 (OH) 12 have been assembled. In this study, two different procedures for PVA membrane cross-linking were applied including a thermal treatment, with elevated temperatures (140 °C 100 min) and chemical treatment with the addition of 35% maleic acid to the polymer matrix and thermal treatment (110 °C 120 min). The structure of the membranes was examined by wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). Thermal properties and stability were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that fullerenol, being an effective cross-linker for PVA, prevented the crystallization of the polymer during annealing, resulting in the increase of membrane permeability for chemically cross-linked membranes. Transport properties of hybrid membranes containing up to 5 wt% fullerenol were studied by the pervaporation of (1) chemical-equilibrium quaternary mixtures of n -propyl acetate, acetic acid, n -propanol and water in order to identify the properties of the membranes used in the hybrid process of esterification+pervaporation, and (2) ternary azeotropic n -propyl acetate– n -propanol–water mixtures. All the membranes were selective with respect to water and the optimal transport properties were obtained for the PVA-5% fullerenol membranes containing maleic acid.

Nanoparticle embedded carbon nanotube papers can produce flexible functional films, whose function is based on the electronic coupling of the nanoparticles with the network of carbon nanotubes. Here we report on the expansion of a synergistic light-free catalyst system that requires both the molecular wire capability of multi-walled carbon nanotubes and the piezoelectric properties of ZnO nanoparticles. The electron–hole pairs can be induced by the piezoelectric effect of ZnO nanoparticles under the effect of pressure. The strong oxidizing radicals interact with the electron–hole pairs and aqueous solution to induce the degradation of methylene blue without the requirement of light. This study highlights the use of nanoparticles for the piezoelectric – light free catalyst system and the limitations of increased nanoparticle loading on the catalytic degradation of methylene blue.

Polyhydroxy fullerenes such as fullerenol C60(OH)22–24 have helped to bridge the gap between fullerenes and their innate solubility issues, where fullerenol solubility in water is 50 mg/ml whereas C60 solubility is 1.3 × 10−11 mg/ml. The improved solubility of these fullerene derivatives allows them to be better integrated into composite materials. Here we investigated the transport properties of cross-linked fullerenol–polyvinyl alcohol membranes with the addition of maleic acid for increased stability. High humidity causes the mechanical properties of polyvinyl alcohol to decrease. Using fullerenol as a cross-linker, we were able to decrease the sorption of water with these PVA membranes.

The commercial market of Sn–Pb solder is gradually decreasing due to its toxicity, calling for Pb-free substitute materials. Sn–Ag alloy is a potential candidate in terms of good mechanical property. The major problematic issue of using Sn–Ag is their high melting temperature, consequently this study is dedicated to lowering the melting temperature of Sn3.5Ag (wt%) alloy by developing nanomaterials using a chemical reduction approach. The resultant nanocrystalline Sn3.5Ag is characterized by field emission scanning electron microscope. The size dependence of the melting temperature is discussed based on differential scanning calorimetry results. We have reduced the melting temperature to 209.8 °C in the nanocrystalline Sn3.5Ag of (32.4 ± 8.0) nm, compared to ~221 °C of the bulk alloy. The results are consistent with the prediction made by a relevant theoretical model, and it is possible to further lower the melting temperature using the chemical reduction approach developed by this study.

Carbon nanotube papers have many potential applications from actuators to electrodes. Cross-linked papers with embedded nanoparticles are now being investigated for use in these applications. Here we report on the development of piezoelectric multi-walled carbon nanotube paper. The piezoelectric effect of the paper was enhanced by four orders of magnitude by embedding zinc oxide nanoparticles into the carbon nanotube network, resulting in a simple method for producing flexible piezoelectric carbon nanotube paper.

High content carbon nanotubes mats have been produced to a range of thicknesses and diameters by covalent bonded cross-linking of thiolated multi-walled carbon nanotubes. The Michael addition pathway was used to cross-link benzoquinone to thiol groups attached to the surface of the nanotubes. The mats were characterized by a variety of techniques including X-ray photoelectron spectroscopy, tensile strength as well as qualitative structural analysis by scanning electron microscopy. It was found that the optimum ratio by weight for cross-linking benzoquinone to thiolated carbon nanotubes was ca. 5:1. This work provided a simple route to the production of mats without high pressure processing or irradiation techniques generally used to produce Buckypaper which can require pressure control chambers, argon and hydrogen ion beams and high temperatures. The mat surface can be further functionalized with nanoparticles to form advanced carbon composite materials.

Large-scale production of pure carbon spheres, with diameters from 50 nm to 1 μm, has been achieved via direct pyrolysis of a wide range of hydrocarbons, including styrene, toluene, benzene, hexane, cyclohexane and ethene, in the absence of catalyst. Specific systematic studies using styrene as the feedstock indicate that the sizes of the resulting of carbon nanospheres can be controlled quite well by adjusting the experimental conditions. The resulting materials have been fully characterized using SEM, TEM, AFM, HRTEM, EDX, elemental analysis, density measurement, XPS, FTIR, XRD, Raman, and TGA. The results show that the spheres, which are 99% carbon, consist of concentric incompletely closed graphitic shells. The dangling bonds on the edges of the shells result in high chemical reactivity.

Bioinspiration: Polar assembly (a feature of many natural protein-based fibrous structures, such as actin, microtubules, intermediate filaments, and collagens) is demonstrated in a straightforward, synthetic, peptide-based fiber system of de novo design (see false-color confocal-microscope image of fibers). This finding opens up possibilities for engineering self-assembling soft materials from the bottom up and with nano-to-microscale precision.

Here we report on the construction and operation of a cross-linked aminated multi-walled carbon nanotube paper as a hydrogen sensor. The incorporation of palladium onto the surface of the paper resulted in p-type conduction as the resistance of the paper was measured, under exposure to hydrogen gas. When palladium nanocrystals were embedded into the cross-linked paper, n-type conduction was observed during hydrogen sensing. This investigation highlights the next stage in the development of functional nanotube paper.

With careful removal of acid-oxidative lattice fragments and use of acid–base titrations, the covalent reactivity of covalently bound carboxylic groups on multi-walled carbon nanotube surfaces has been directly confirmed, including intermediate states, for carbodiimide promoted amidation reactions.

This is the final version of the article. Available from Hindawi Publishing Corporation via the DOI in this record.

Understanding the compatibility between spider silk and conducting materials is essential to advance the use of spider silk in electronic applications. Spider silk is tough, but becomes soft when exposed to water. Here we report a strong affinity of amine-functionalised multi-walled carbon nanotubes for spider silk, with coating assisted by a water and mechanical shear method. The nanotubes adhere uniformly and bond to the silk fibre surface to produce tough, custom-shaped, flexible and electrically conducting fibres after drying and contraction. The conductivity of coated silk fibres is reversibly sensitive to strain and humidity, leading to proof-of-concept sensor and actuator demonstrations., The use of spider silk in electronic devices is dependent on its compatibility with electrically conductive materials. Here the authors modify spider silk with carbon nanotubes to produce a strong, flexible and electrically conductive thread.

Concerns about depleting natural resources have been circulating for decades with alarming predictions that have turned out to be less than accurate. What has become clear, however, is the need for a decrease in the utility of a fossil based economy and a focus on a more sus‐ tainable one. This chapter reviews some of the recent progress made in the use of intercon‐ nected carbon nanotubes (CNTs) in the hydrogen, photovoltaics and thermoelectric alternative energy based economies.

Nanoparticles of a promising lead-free solder alloy (Sn3.5Ag (wt.%, SnAg) and Sn3.0Ag0.5Cu (wt.%, SAC)) were synthesized through a chemical reduction method by using anhydrous ethanol and 1,10-phenanthroline as the solvent and surfactant, respectively. To illustrate the formation process of Sn-Ag alloy based nanoparticles during the reaction, X-ray diffraction (XRD) was used to investigate the phases of the samples in relation to the reaction time. Different nucleation and growth mechanisms were compared on the formation process of the synthesized nanoparticles. The XRD results revealed different reaction process compared with other researchers. There were many contributing factors to the difference in the examples found in the literature, with the main focus on the formation mechanism of crystal nuclei, the solubility and ionizability of metal salts in the solvent, the solid solubility of Cu in Ag nuclei, and the role of surfactant on the growth process. This study will help define the parameters necessary for the control of both the composition and size of the nanoparticles.

Since the inception of the research field on carbon nanotubes (CNTs), there has been an enormous effort to understand how the tubes form and how to best garner their unique electronic and mechanical properties. It soon became apparent that in order to develop the next generation of functional materials, a way to modify the surface of the tubes and connect them was required. The development of the oxidation process with acids was the first revolution in the field of CNTs, potentially opening the door to an extensive library of modifications. Research progressed by integrating the nanotubes into composites at low concentrations with some success, but the goal of producing high nanotube component covalently cross-linked materials was still problematic. Two decades after the report by Sumio Ijima on their discovery, cross-linked CNT materials are still difficult to produce, and this has shifted the field towards a back-to-basics approach to try and solve the problem. One key problem identified was the presence of lattice fragments immobilized on the surface of the CNTs (Fig. 1.). The current methods of characterization such as X-ray photoelectron, Infrared and Raman spectroscopy are indirect and generally fail to distinguish between the surface attached functional groups and oxidized lattice fragments. A CNT washing technique has been developed to remove these fragments and any electrostatically attached products to allow pure covalent interactions with the surface of the nanotube (Wang et al., 2010). With an industry now thriving on the production of cheap functionalized carbon vapor deposition (CVD) CNTs, priced according to the percentage surface functionalization, and the decline in published materials on arc-produced CNTs, the need for effective characterization and quality control increases. It is the intention of this chapter to review some of the successful approaches used to crosslink CNTs with a focus on the importance of the chemistry and techniques involved, and highlight two areas of research we are currently investigating at Florida State University.

An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (MWNTs), resulting in various linear or hyperbranched polycondensed polymers [e.g., polyureas, polyurethanes, and poly(urea-urethane)-bonded carbon nanotubes]. The quantity of the grafted polymer can be easily controlled by the feed ratio of monomers. As a typical example, the polyurea-functionalized MWNTs were measured and characterized in detail. The oxidized MWNTs (MWNT-COOH) were converted into acyl chloride-functionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH2). In the presence of MWNT-NH2, the polyurea was covalently coated onto the surfaces of the nanotube by in situ polycondensation of diisocyanate [e.g., 4,4'-methylenebis(phenylisocyanate)] and 1,6-diaminohexane, followed by the removal of free polymer via repeated filtering and solvent washing. The coated polyurea content can be controlled to some extent by adjusting the feed ratio of the isocyanato and amino groups. The structure and morphology of the resulting nanocomposites were characterized by FTIR, NMR, Raman, confocal Raman, TEM, EDS, and SEM measurements. The polyurea-coated MWNTs showed interesting self-assembled flat- or flowerlike morphologies in the solid state. The signals corresponding to that of the D and G bands of the carbon nanotubes were strongly attenuated after polyurea was chemically tethered to the MWNT surfaces. Comparative experiments showed that the grafted polymer species and structures have a strong effect on the Raman signals of polymer-functionalized MWNTs.