Synthesis and Optical Properties of Highly Stabilized Peptide- Coated Silver Nanoparticles

The interaction between the silver nanoparticle and peptide surfaces has been of increased interest for the applications of bionanotechnology and tissue engineering. In order to completely understand such interactions, we have examined the optical properties of peptide-coated silver nanoparticles. However, the effect of peptide binding motif upon the silver nanoparticles surface characteristics and physicochemical properties of these nanoparticles remains incompletely understood. Here, we have fabricated sodium citrate stabilized silver nanoparticles and coated with peptide IVD (ID3). The optical properties of these peptide-capped nanomaterials were characterized by UV-visible, transmission electron microscopy (TEM), and z-potential measurement. The results indicate that the interface of silver nanoparticles (AgNP)-peptide is generated using ID3 peptide and suggested that the reactivity of peptide is governed by the conformation of the bound peptide on the silver nanoparticle surface. The interactions of peptide-nanoparticle would potentially be used to fabricate specific functionality into the various peptide-capped nanomaterials and antibacterial applications

Studies of Nanocomposites of Carbon Nanotubes and a Negative Dielectric Anisotropy Liquid Crystal

The complex specific heat is reported over a wide temperature range for a negative dielectric anisotropy alkoxyphenylbenzoate liquid crystal (9OO4) and carbon nanotube (CNT) composites as a function of carbon nanotube concentration. It has been observed that the combination of nanotubes (CNT) and liquid crystal (LC) provides a very useful way to align CNTs and also dramatically increases the order in the liquid crystal performance, which is useful in liquid display technology (LCD). The calorimetric scans were performed between 25 and 95°C temperatures, first allowed cooling and then heating for CNT concentration ranging from ϕw = 0 to 0.2 wt%. All 9OO4/CNT composite mesophases have transition temperatures about 1 K higher and a crystallization temperature 4 K higher as compared to the pure 9OO4 liquid crystal. A strongly first-order specific heat feature is observed, which is 0.5 K higher than in the pure 9OO4. The transition enthalpy for the composite mesophases is observed 10% lower than the pure liquid crystal. We interpret that these results arising from the LC-CNT surface interaction lead to pinning orientational order uniformly along the CNT, without pinning the position of the 9OO4 molecule. These effects of incorporating CNTs with LC are likely due to elastic coupling between CNT and LC. These effects of incorporating CNTs into LCs are likely due to an "anisotropic orientational" coupling between CNT and LC, the change in the elastic properties of composites and thermal anisotropic properties of the CNTs

Studies of Electrical and Thermal Conductivities of Sheared Multi-Walled Carbon Nanotube with Isotactic Polypropylene Polymer Composites

Polymer nanocomposite materials of higher thermal and electrical transport properties are important to nanotechnology applications such as thermal management, packaging, labelling and the textile industry. In this work, thermal and electrical conductivities in nanocomposites of multiwalled carbon nanotubes (MWCNT) and isotactic polypropylene (iPP) are investigated in terms of MWCNT loading, temperature dependence, and anisotropy caused by melt shearing. IPP/MWCNT nanocomposites show a significant increase in thermal and electrical conductivity with increasing MWCNT loading, reaching 17.5 W/m K and 10−6 S/m, respectively, at a MWCNT 5.0 weight percentage at 40°C. The increase in MWCNT/iPP is more than would be expected based on the additivity rule, and suggests a reduction of the interfacial thermal electrical resistance at nanotube-nanotube junctions and the nanotube-matrix interface. The anisotropy in both conductivities was observed to be larger at low temperature and to disappear at higher temperature due to isotropic electrical and thermal contact in both directions. Oriented MWCNT/iPP nanocomposites exhibit higher electrical and thermal conductivities, attributed primarily by orientation of nanotubes due to the shearing fabrication process

Calorimetric and dielectric study of a negative dielectric anisotropy alkoxy-phenyl-benzoate liquid crystal

Modulated Differential Scanning Calorimetry (MDSC) and dielectric spectroscopy have been used to measure the complex specific heat and dielectric constant over a wide temperature range on heating and cooling for a negative dielectric anisotropy alkoxyphenylbenzoate liquid crystal, denoted 9OO4. The MDSC experimental parameters were varied in order to yield quasi-static specific heat results and the same base scan rate was used for the dielectric measurements. On cooling, 9OO4 exhibits a typical weakly first-order isotropic to nematic then a continuous nematic to smectic-A phase sequence followed by a monotropic smectic-C and smectic-B phases before crystallizing. The smectic-B conversion is very slow, even for our quasi-static scan parameters. On heating, the crystal phase super-heats and exhibits a strong first-order transition into an unknown smectic phase that itself converts to the smectic-A phase via a first-order, highly rate dependent, phase transition. The nematic-smectic-A transition has an unusual character given the molecular structure of 9OO4 that may be related to combination of molecular structure and a negative dielectric anisotropy

Thermal Physical Properties Of Nanocomposites Of Complex Fluids

Composites of nanoparticles with complex fluids represent a unique physical system where thermal physical properties of the components partially or fully mix and new behavior can emerge. Traditional composites are relatively well understood as the superposition, weighted by volume or mass, of the components properties and the interfacial interactions play the role of holding the composite together. As the filler component, nanoparticle, decreases in size, the surface area begins to dominate, leading to unique behavior of the nanocomposites. The richness of the nanocomposites that can be designed by coupling various nanoparticles and complex fluid materials opens a wide field of active research. This dissertation presents a series of experimental studies on various nanocomposites using modulated differential scanning calorimetry, spectroscopic ellipsometry, dielectric spectroscopy, polarizing microscopy, and conductivity measurements of nanoparticles such as multi-wall carbon nanotubes and quantum dots on the phase transitions of several liquid crystals and polymers. The liquid crystals (LCs) and liquid crystalline polymer (LCP) of interest are: negative dielectric anisotropy alkoxyphenylbenzoate (9OO4), octylcyanobiphenyl (8CB), decylcyanobiphenyl (10CB), and isotactic polypropylene (iPP) which can form smectic liquid crystal (LC) phase. Studies have been carried out as a function of concentration and temperature spanning through various ordered phases. The results indicate a mixture of ordering and disordering effects of the nanoparticles on the phases of the complex fluids. In 9OO4/CNT system, dipole moment of liquid crystal and graphene like surface can allow a random dispersion of CNT to promote both orientational and positional order. For nCB/CNT, nCB/Quantum dot (QD) systems, nanoparticles induce net disordering effect in LC media. The effect of QDs on LC depends on the anchoring conditions and the QDs size. The results clearly demonstrate that the nematic phase imposes self-assembly on QDs to form one dimensional arrays. This leads to net disordering effect. The thermal/electrical conductivity changes in thin films of iPP/CNT sheared/un-sheared samples and it also varies with temperature for the purpose of inducing anisotropy of those properties in parallel and perpendicular to average orientation. The percolation threshold is clearly pronounced in both conductivities due to pressing and shearing treatment of the films. This will further our abilities to nano-engineer material for many important applications

Engineering micro/nano-fibrous scaffolds with silver coating for tailored wound repair applications

Electrospun scaffolds originating from polymeric amalgams, specifically poly(glycerol sebacate/poly(ε-caprolactone) (PGS/PCL) and poly(methyl methacrylate)–poly(ε-caprolactone) (PMMA/PCL), have emerged as a versatile substrate within the realm of biomedical tissue engineering. Their salience is underscored by their remarkable thermal, optical, and mechanical attributes. In this investigation, we harnessed conventional electro-spinning methodologies to fabricate nano/micro-fibrous scaffolds from a hybrid composite, amalgamating PMMA/PCL and PGS/PCL fibers. A pivotal innovation lay in the precise deposition of silver nanoparticles (AgNPs) on one facet of these scaffolds, endowing them with anti-bacterial functionality. This AgNP coating not only forestalled melting proclivities but also meticulously tuned structural facets, engendering a diminution in pore diameter and augmentation in fiber diameter, thereby engendering an elevation in thermo-mechanical performance. Comparative scrutiny delineated that the PMMA/PCL composite fibrous scaffolds manifested superior mechanical attributes, including augmented modulus (E) and ultimate tensile strength (UTS), accompanied by attenuated tensile strain, obviating the requisite for supplementary post-processing steps. These AgNP-endowed composite fibrous scaffolds engender sanguine prospects for biomedical applications, encompassing surgical meshes, bandages, and band-aids, underpinned by their amplified anti-bacterial characteristics, which are instrumental in the context of wound healing

Facile Synthesis of Silver Nanoparticles Using Green Tea Leaf Extract and Evolution of Antibacterial Activity

The scientific society is exploiting the use of nanoparticles in nano-medicine and biomedical applications. In the field of biomaterial and bio-nanotechnology, silver nanoparticles (AgNPs) are playing an important role due to their potential physical, chemical, and biological properties ranging in activities from antibacterial, antiviral, antifungal, and anticancer treatment. Green synthesis technology is one of the most cost-effective, eco-friendly, and biologically safe methods. Green tea leaf extract can reduce silver to AgNPs and enhance antibacterial activity. In this work, we demonstrate the antibacterial activity effect employing green synthesis of AgNPs with green tea leaf extract. The UV–Vis and FTIR results showed, confirming the formation of AgNPs and the presence of chemical groups enhancing the antibacterial activity of AgNPs. The synthesized AgNPs with green tea leaf extract were crystalline with a quasi-spherical shape with a diameter from 30 to 150 nm. The antibacterial activity of the AgNPs in three different concentrations showed that the 120 mg/ml sample possesses higher antibacterial activity (significantly high killing ability) against E. coli than chemically produced AgNPs. These results confirm a more significant antibacterial effect of the biogenic AgNPs with low cytotoxicity than the AgNPs produced chemically. These findings can be used to treat chronic infections, diseases, and other biomedical applications. Graphical Abstract: [Figure not available: see fulltext.]