3D printing has transitioned from the commercial and educational sectors toward tools for materia... more 3D printing has transitioned from the commercial and educational sectors toward tools for materials science. The technologies available for 3D printing have evolved rapidly, facilitating the incorporation of new materials and functionalities into filaments and resins. As the cost of 3D printing decreases, and the technologies supporting high-resolution printing become industry standard, the push toward 4D printing, a subcategory of 3D printing, that enables the fabrication of components through multiple techniques and materials will transform the energy sector. 3D printing is no longer limited to the use of plastics, and the fabrication of metal, graphene, and hybrid architectures for use as electrodes is
ECS Journal of Solid State Science and Technology, 2017
In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Pr... more In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Prize in Chemistry for the discovery of fullerenes. The advent of these new forms of carbon heralded a race to understand the physical and chemical properties. C 60 is virtually insoluble in polar solvents but is partially soluble in benzene, toluene, and carbon disulfide. This made the processing of fullerenes for new applications fairly problematic. However, the physical and chemical properties of these cage structures may be tailored for a wide range of applications. Some of the difficulties in processing have been overcome by using novel fullerene derivatives. The functionalization of the fullerene core with different chemical moieties provided a vector toward potential applications in drug delivery, optoelectronics, electrochemistry and organic photovoltaics. In this review, we will take a closer look at the features of some of the fullerene derivatives that have reinvigorated the field of fullerene research. Water-soluble polyhydroxylated fullerenes such as fullerenol have demonstrated the potential for good electron transfer and optical transmission, while hydrophobic fullerene derivatives have shown promising avenues for catalytic applications. 2015 marked the 30 th anniversary of the discovery of fullerenes, with celebrations around the world including an event by the Royal Society of Chemistry, bringing together many of Sir Harold Kroto's former students. The event also coincided with the recent discovery of C 60 + in space after a complex twenty-year search. It is with sadness that we, Harry's Research Group at Florida State University, and his international collaborators, reflect on the passing of Sir Harold Kroto. His dedication to science and commitment to science communication through the VEGA Science Trust and the Global Educational Outreach for Science Engineering and Technology (GEOSET) initiative help to raise awareness of the challenges for science in the modern world. We will continue to inspire young students through outreach activities he initiated.
Bulletin of the American Physical Society, Mar 20, 2009
The self-assembly of semi-flexible filaments, such as F-actin, in the presence of cross-linkers h... more The self-assembly of semi-flexible filaments, such as F-actin, in the presence of cross-linkers has been studied experimentally and via molecular dynamics simulation. Several imaging techniques including fluorescence and electron microscopy have been used to elucidate the structural properties of formed bundles and networks of filaments. With the help of simulation we are able to observe the dynamical process of the self-assembly and study the driving forces behind filament aggregation. The roles of different parameters such as cross-linker density and filament length have been investigated, determining the assembled system properties. We find both of these parameters to play a key role in the final structure formation. Understanding the mechanism for the self-assembly of these semi-flexible filaments will be very useful in the application of developing a new class of biological materials.
Journal of Solid State Electrochemistry, Jan 31, 2019
A noncovalent interaction based self-assembled ruthenium (II) phthalocyanine (RuPc) and N-pyridyl... more 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 TiO 2 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 TiO 2. 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.
Cross-linked papers with embedded nanoparticles are now being investigated for use in these appli... more 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.
ABSTRACT Abstract Nanoparticle embedded carbon nanotube papers can produce flexible functional fi... more ABSTRACT Abstract 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.
ABSTRACT Polyhydroxy fullerenes such as fullerenol C60(OH)22–24 have helped to bridge the gap bet... more ABSTRACT 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.
In this study, the in situ sol−gel method has been deployed to prepare the titanium dioxide/multi... more In this study, the in situ sol−gel method has been deployed to prepare the titanium dioxide/multiwalled carbon nanotubes (TiO 2 /MWCNTs) nanocomposite (NCs) powders with varying content of MWCNTs (0.01−1.0 wt %), to construct the dye-sensitized solar cells (DSSCs). First, binder-free NCs were deposited on a transparent-conducting F:SnO 2 (FTO) glass substrate by a doctor-blade technique and then anchored with Ru(II)-based dyes to either N719 or ruthenium phthalocyanine (RuPc). The structural and optical properties and interconnectivity of the materials within the composite are investigated thoroughly by various spectral techniques (XRD, XPS, Raman, FT-IR, and UV−vis), electron microscopy (HRTEM), and BET analysis. The experimental results suggest that the ratio of MWCNTs and TiO 2 in NCs, morphology, and their interconnectivity influenced their structural, optical, and photovoltaic properties significantly. Finally, the photovoltaic performances of the assembled DSSCs with different content of MWCNTs to TiO 2 films anchored with two different dyes were tested under one sun irradiation (100 mW/cm 2). The measured current−voltage (IV) curve and incident photon-to-current conversion efficiency (IPCE) spectra of TiO 2 /0.1 wt % MWCNTs (T@0.1 C) for N719 dye show three times more power conversion efficiency (η = 6.21%) which is opposed to an efficiency (η = 2.07%
ECS Journal of Solid State Science and Technology, 2017
In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Pr... more In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Prize in Chemistry for the discovery of fullerenes. The advent of these new forms of carbon heralded a race to understand the physical and chemical properties. C 60 is virtually insoluble in polar solvents but is partially soluble in benzene, toluene, and carbon disulfide. This made the processing of fullerenes for new applications fairly problematic. However, the physical and chemical properties of these cage structures may be tailored for a wide range of applications. Some of the difficulties in processing have been overcome by using novel fullerene derivatives. The functionalization of the fullerene core with different chemical moieties provided a vector toward potential applications in drug delivery, optoelectronics, electrochemistry and organic photovoltaics. In this review, we will take a closer look at the features of some of the fullerene derivatives that have reinvigorated the field of fullerene research. Water-soluble polyhydroxylated fullerenes such as fullerenol have demonstrated the potential for good electron transfer and optical transmission, while hydrophobic fullerene derivatives have shown promising avenues for catalytic applications. 2015 marked the 30 th anniversary of the discovery of fullerenes, with celebrations around the world including an event by the Royal Society of Chemistry, bringing together many of Sir Harold Kroto's former students. The event also coincided with the recent discovery of C 60 + in space after a complex twenty-year search. It is with sadness that we, Harry's Research Group at Florida State University, and his international collaborators, reflect on the passing of Sir Harold Kroto. His dedication to science and commitment to science communication through the VEGA Science Trust and the Global Educational Outreach for Science Engineering and Technology (GEOSET) initiative help to raise awareness of the challenges for science in the modern world. We will continue to inspire young students through outreach activities he initiated.
Prize in chemistry. The subsequent years have seen a journey of discovery in the field of nanosci... more Prize in chemistry. The subsequent years have seen a journey of discovery in the field of nanoscience and nanotechnology, a journey that continues with the recent discovery of C 60 ions in space.
Large-scale production of pure carbon spheres, with diameters from 50 nm to 1 lm, has been achiev... more Large-scale production of pure carbon spheres, with diameters from 50 nm to 1 lm, 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.
3D printing is a revolutionary technology for the consumer and industrial markets. As the technol... more 3D printing is a revolutionary technology for the consumer and industrial markets. As the technology for 3D printing has expanded, the need for multi-materials that support fused deposition modeling and other forms of additive manufacturing is increasing. 3D printing filaments infused with carbon nanotubes and graphene are now commercially available, with the promise of producing conductive composites. This chapter explores some of the research, products, and challenges involved in bringing the next generation of functional printing materials to the consumer market.
An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (M... more 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 chloridefunctionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl 2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH 2). In the presence of MWNT-NH 2 , 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 flator 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.
The commercial market of Sn-Pb solder is gradually decreasing due to its toxicity, calling for Pb... more The commercial market of Sn-Pb solder is gradually decreasing due to its toxicity, calling for Pb-free substitute materials. SnAg alloy is a potential candidate in terms of good mechanical property. The major problematic issue of using SnAg 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.
ABSTRACT Hybrid membranes based on composites of polyvinyl alcohol (PVA) and low-hydroxylated ful... more ABSTRACT Hybrid membranes based on composites of polyvinyl alcohol (PVA) and low-hydroxylated fullerenol C60(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.
Self-assembling systems are found extensively in biology. [1] An improved understanding of these ... more Self-assembling systems are found extensively in biology. [1] An improved understanding of these systems would fuel efforts to engineer novel, bioinspired assemblies through de novo design. Interest in the area is intense because an ability to engineer or design water-soluble self-assembling systems offers routes to novel biomaterials with potential applications in nanobiotechnology. [2-6] Self-assembling systems based on peptides, proteins, DNA, and RNA are all being explored. [2-6] Furthermore, "living templates", namely fungal hyphae, are being used to direct the hierarchical assembly of nanoparticles. [7] Our focus has been on peptide-based assemblies. [8-10] Specifically, we are interested in making self-assembling fibers and networks from straightforward, synthetically accessible peptide building blocks. Considerable work has been done to mimic fibrous protein assemblies by using predominantly b-structured peptides that form amyloid-like fibrils. [2, 11, 12] Relatively less has been done with a-helix-based assemblies. [3, 8, 13] We have focused on fibrous assemblies based on the a-helical coiled coil, which is a widespread and well-understood proteinprotein interaction motif. [14-16] Specifically, we have combined rules for coiled-coil assembly to design a self-assembling-fiber (SAF) system comprising two complementary peptides, SAF-p1 and SAF-p2. [8] Unlike natural and previously designed coiled coils, which form blunt-ended structures, [14, 17] the SAF peptides were engineered to make offset dimers with complementary sticky ends to promote longitudinal assembly into fibers (Figure 1). Helical assembly was confirmed by using circular dichroism spectroscopy and X-ray fiber diffraction, [8] and
Nanoparticles of a promising lead-free solder alloy (Sn3.5Ag (wt.%, SnAg) and Sn3.0Ag0.5Cu (wt.%,... more 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 SnAg 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.
3D printing has transitioned from the commercial and educational sectors toward tools for materia... more 3D printing has transitioned from the commercial and educational sectors toward tools for materials science. The technologies available for 3D printing have evolved rapidly, facilitating the incorporation of new materials and functionalities into filaments and resins. As the cost of 3D printing decreases, and the technologies supporting high-resolution printing become industry standard, the push toward 4D printing, a subcategory of 3D printing, that enables the fabrication of components through multiple techniques and materials will transform the energy sector. 3D printing is no longer limited to the use of plastics, and the fabrication of metal, graphene, and hybrid architectures for use as electrodes is
ECS Journal of Solid State Science and Technology, 2017
In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Pr... more In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Prize in Chemistry for the discovery of fullerenes. The advent of these new forms of carbon heralded a race to understand the physical and chemical properties. C 60 is virtually insoluble in polar solvents but is partially soluble in benzene, toluene, and carbon disulfide. This made the processing of fullerenes for new applications fairly problematic. However, the physical and chemical properties of these cage structures may be tailored for a wide range of applications. Some of the difficulties in processing have been overcome by using novel fullerene derivatives. The functionalization of the fullerene core with different chemical moieties provided a vector toward potential applications in drug delivery, optoelectronics, electrochemistry and organic photovoltaics. In this review, we will take a closer look at the features of some of the fullerene derivatives that have reinvigorated the field of fullerene research. Water-soluble polyhydroxylated fullerenes such as fullerenol have demonstrated the potential for good electron transfer and optical transmission, while hydrophobic fullerene derivatives have shown promising avenues for catalytic applications. 2015 marked the 30 th anniversary of the discovery of fullerenes, with celebrations around the world including an event by the Royal Society of Chemistry, bringing together many of Sir Harold Kroto's former students. The event also coincided with the recent discovery of C 60 + in space after a complex twenty-year search. It is with sadness that we, Harry's Research Group at Florida State University, and his international collaborators, reflect on the passing of Sir Harold Kroto. His dedication to science and commitment to science communication through the VEGA Science Trust and the Global Educational Outreach for Science Engineering and Technology (GEOSET) initiative help to raise awareness of the challenges for science in the modern world. We will continue to inspire young students through outreach activities he initiated.
Bulletin of the American Physical Society, Mar 20, 2009
The self-assembly of semi-flexible filaments, such as F-actin, in the presence of cross-linkers h... more The self-assembly of semi-flexible filaments, such as F-actin, in the presence of cross-linkers has been studied experimentally and via molecular dynamics simulation. Several imaging techniques including fluorescence and electron microscopy have been used to elucidate the structural properties of formed bundles and networks of filaments. With the help of simulation we are able to observe the dynamical process of the self-assembly and study the driving forces behind filament aggregation. The roles of different parameters such as cross-linker density and filament length have been investigated, determining the assembled system properties. We find both of these parameters to play a key role in the final structure formation. Understanding the mechanism for the self-assembly of these semi-flexible filaments will be very useful in the application of developing a new class of biological materials.
Journal of Solid State Electrochemistry, Jan 31, 2019
A noncovalent interaction based self-assembled ruthenium (II) phthalocyanine (RuPc) and N-pyridyl... more 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 TiO 2 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 TiO 2. 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.
Cross-linked papers with embedded nanoparticles are now being investigated for use in these appli... more 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.
ABSTRACT Abstract Nanoparticle embedded carbon nanotube papers can produce flexible functional fi... more ABSTRACT Abstract 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.
ABSTRACT Polyhydroxy fullerenes such as fullerenol C60(OH)22–24 have helped to bridge the gap bet... more ABSTRACT 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.
In this study, the in situ sol−gel method has been deployed to prepare the titanium dioxide/multi... more In this study, the in situ sol−gel method has been deployed to prepare the titanium dioxide/multiwalled carbon nanotubes (TiO 2 /MWCNTs) nanocomposite (NCs) powders with varying content of MWCNTs (0.01−1.0 wt %), to construct the dye-sensitized solar cells (DSSCs). First, binder-free NCs were deposited on a transparent-conducting F:SnO 2 (FTO) glass substrate by a doctor-blade technique and then anchored with Ru(II)-based dyes to either N719 or ruthenium phthalocyanine (RuPc). The structural and optical properties and interconnectivity of the materials within the composite are investigated thoroughly by various spectral techniques (XRD, XPS, Raman, FT-IR, and UV−vis), electron microscopy (HRTEM), and BET analysis. The experimental results suggest that the ratio of MWCNTs and TiO 2 in NCs, morphology, and their interconnectivity influenced their structural, optical, and photovoltaic properties significantly. Finally, the photovoltaic performances of the assembled DSSCs with different content of MWCNTs to TiO 2 films anchored with two different dyes were tested under one sun irradiation (100 mW/cm 2). The measured current−voltage (IV) curve and incident photon-to-current conversion efficiency (IPCE) spectra of TiO 2 /0.1 wt % MWCNTs (T@0.1 C) for N719 dye show three times more power conversion efficiency (η = 6.21%) which is opposed to an efficiency (η = 2.07%
ECS Journal of Solid State Science and Technology, 2017
In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Pr... more In 1996 Sir Harold W. Kroto, Robert F. Curl and Richard E. Smalley were honored with the Nobel Prize in Chemistry for the discovery of fullerenes. The advent of these new forms of carbon heralded a race to understand the physical and chemical properties. C 60 is virtually insoluble in polar solvents but is partially soluble in benzene, toluene, and carbon disulfide. This made the processing of fullerenes for new applications fairly problematic. However, the physical and chemical properties of these cage structures may be tailored for a wide range of applications. Some of the difficulties in processing have been overcome by using novel fullerene derivatives. The functionalization of the fullerene core with different chemical moieties provided a vector toward potential applications in drug delivery, optoelectronics, electrochemistry and organic photovoltaics. In this review, we will take a closer look at the features of some of the fullerene derivatives that have reinvigorated the field of fullerene research. Water-soluble polyhydroxylated fullerenes such as fullerenol have demonstrated the potential for good electron transfer and optical transmission, while hydrophobic fullerene derivatives have shown promising avenues for catalytic applications. 2015 marked the 30 th anniversary of the discovery of fullerenes, with celebrations around the world including an event by the Royal Society of Chemistry, bringing together many of Sir Harold Kroto's former students. The event also coincided with the recent discovery of C 60 + in space after a complex twenty-year search. It is with sadness that we, Harry's Research Group at Florida State University, and his international collaborators, reflect on the passing of Sir Harold Kroto. His dedication to science and commitment to science communication through the VEGA Science Trust and the Global Educational Outreach for Science Engineering and Technology (GEOSET) initiative help to raise awareness of the challenges for science in the modern world. We will continue to inspire young students through outreach activities he initiated.
Prize in chemistry. The subsequent years have seen a journey of discovery in the field of nanosci... more Prize in chemistry. The subsequent years have seen a journey of discovery in the field of nanoscience and nanotechnology, a journey that continues with the recent discovery of C 60 ions in space.
Large-scale production of pure carbon spheres, with diameters from 50 nm to 1 lm, has been achiev... more Large-scale production of pure carbon spheres, with diameters from 50 nm to 1 lm, 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.
3D printing is a revolutionary technology for the consumer and industrial markets. As the technol... more 3D printing is a revolutionary technology for the consumer and industrial markets. As the technology for 3D printing has expanded, the need for multi-materials that support fused deposition modeling and other forms of additive manufacturing is increasing. 3D printing filaments infused with carbon nanotubes and graphene are now commercially available, with the promise of producing conductive composites. This chapter explores some of the research, products, and challenges involved in bringing the next generation of functional printing materials to the consumer market.
An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (M... more 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 chloridefunctionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl 2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH 2). In the presence of MWNT-NH 2 , 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 flator 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.
The commercial market of Sn-Pb solder is gradually decreasing due to its toxicity, calling for Pb... more The commercial market of Sn-Pb solder is gradually decreasing due to its toxicity, calling for Pb-free substitute materials. SnAg alloy is a potential candidate in terms of good mechanical property. The major problematic issue of using SnAg 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.
ABSTRACT Hybrid membranes based on composites of polyvinyl alcohol (PVA) and low-hydroxylated ful... more ABSTRACT Hybrid membranes based on composites of polyvinyl alcohol (PVA) and low-hydroxylated fullerenol C60(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.
Self-assembling systems are found extensively in biology. [1] An improved understanding of these ... more Self-assembling systems are found extensively in biology. [1] An improved understanding of these systems would fuel efforts to engineer novel, bioinspired assemblies through de novo design. Interest in the area is intense because an ability to engineer or design water-soluble self-assembling systems offers routes to novel biomaterials with potential applications in nanobiotechnology. [2-6] Self-assembling systems based on peptides, proteins, DNA, and RNA are all being explored. [2-6] Furthermore, "living templates", namely fungal hyphae, are being used to direct the hierarchical assembly of nanoparticles. [7] Our focus has been on peptide-based assemblies. [8-10] Specifically, we are interested in making self-assembling fibers and networks from straightforward, synthetically accessible peptide building blocks. Considerable work has been done to mimic fibrous protein assemblies by using predominantly b-structured peptides that form amyloid-like fibrils. [2, 11, 12] Relatively less has been done with a-helix-based assemblies. [3, 8, 13] We have focused on fibrous assemblies based on the a-helical coiled coil, which is a widespread and well-understood proteinprotein interaction motif. [14-16] Specifically, we have combined rules for coiled-coil assembly to design a self-assembling-fiber (SAF) system comprising two complementary peptides, SAF-p1 and SAF-p2. [8] Unlike natural and previously designed coiled coils, which form blunt-ended structures, [14, 17] the SAF peptides were engineered to make offset dimers with complementary sticky ends to promote longitudinal assembly into fibers (Figure 1). Helical assembly was confirmed by using circular dichroism spectroscopy and X-ray fiber diffraction, [8] and
Nanoparticles of a promising lead-free solder alloy (Sn3.5Ag (wt.%, SnAg) and Sn3.0Ag0.5Cu (wt.%,... more 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 SnAg 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.
Uploads
Papers by Steve Acquah