Materials Science Forum Vol. 756

Abstract: Nanoscale particles of gold nowadays dominate a great deal of attention for biomedical applications. Better knowledge of the nano-bio interface will lead to advanced biomedical tools for diagnostic imaging and therapeutics. In this review, recent progress in the elucidating of how size and concentration of gold nanoparticles (AuNPs) affect cellular uptake will be discussed. Due to its small size, AuNPs can be administered conveniently via intravenous injection. The ability to enter cells is one of the factors that determine the clinical utility of nanoparti¬cles (NPs). The size of AuNPs is one of the limitations in the potential use of gold markers for medical imaging or tracking of harder tumors. Within the size range of 10-100 nm, AuNPs of diameter 50 nm demonstrate the highest uptake. Efficient accumulation of AuNPs into cells also can be achieved at higher concentration. The fewer AuNPs are in the solution, the lesser chance for a receptor to receive gold nanoparticle; “mem¬brane wrapping” time is longer, resulting to lower uptake by the cell. Theoretical models support the size- and concentration-dependent NP-uptake. Endocytosis is one of the major pathways for cellular uptake of NPs. NPs are internalized by cells through endocytosis process and trapped in endosomes, which is then fuse with lysosomes for processing before being transported to the cell periphery for excretion. Exocytosis of NPs is also dependent on the size and concentration of the NPs, however, the trend is different compared to endocytosis process. These findings provide useful information in the design and optimization of the NP-uptake at a single cell level for effective applications in imaging, diagnosis, therapeutics, and targeting.

Abstract: Lead (Pb) has been recognized to be acutely toxic to human beings and studies have shown that young children, infants and pregnant women are particularly at risk to unsafe Pb (II) level. Generally, high level of Pb(II) can be removed by using alginate beads. However, at low level, it is not possible to be removed by alginate. For that reason, low concentration (10 ppm) of Pb(II) removal by photocatalytic activity is explored in this work. Cu loaded TiO₂ nanotube was prepared by wet impregnation with different Cu concentration. The initial concentration of Cu involved were 0.01 M, 0.06 M and 0.1 M. For heavy metal removal, the initial concentration of Pb(II) solution used was 10 ppm. The remnant concentration of Pb(II) solution after irradiated under ultraviolet(UV) light was determined by using Atomic Absorption Spectroscopy (AAS). It was observed that the optimal condition of Cu loaded nanotube was at 0.01 M and it exhibited highest removal of Pb(II) with 50%. However, at high Cu concentration(> 0.06 M), it declined the performance of TiO₂ nanotubes for Pb(II) removal. The removal of Pb(II) obtained at 0.06 M and 0.01M was only 23.3% and 17.1%.

Abstract: The tungsten trioxide (WO₃) and copper(II) oxide (CuO) photoelectrodes have been fabricated from acidic aqueous solution of peroxy-tungstate and basic aqueous solution of copper sulphate-lactic acid respectively, by electrodeposition method. The samples produced were calcined at 450 °C for 30 minutes before the deposition of second layer. The CuO was layered on WO₃ sample by electrodeposition of basic aqueous solution of copper sulphate-lactic acid, followed by annealing process at 450 °C for 30 minutes. On the other hand, the WO₃ layer was casted onto CuO sample by sol-gel method and it was annealed at 450 °C for 30 minutes. The resulting samples were then characterized by XRD to confirm their structures. Photoelectrochemical characterization of the WO₃, CuO and WO₃-CuO bilayer photoelectrodes were carried out under 100 W xenon light illumination, in 0.5 M sodium sulphate solution with saturated calomel electrode (SCE) reference electrode and platinum counter electrode. The PEC stability of the electrodes was evaluated at -0.7 V vs SCE under irradiated condition.

Abstract: Nanofibers have proved to be highly efficient due to their enhanced adsorption capacity, because of high pores and very high surfacearea. Pure and Sulphur doped TiO₂ nanofibers were synthesized using electrospinning method in this study to evaluate their destruction potential for H₂S gas, using photocatalysis. Experiments were carried out under laboratory conditions using capillary glass tube reactor under UV light. 97% destruction was achieved using pure TiO₂ nanofibers while the destruction percentage decreased when S-doped TiO₂ nanofibers were replaced with the pure ones. Characterization of the nanofibers before and after running the experiments was carried out using XRD, SEM and EDX techniques. The destruction of H₂S gas was measured in ppm using BioGas Analyser fitted with GPA1.8 Gas pod for H₂S detection.

Abstract: Mononuclearmolybdenum complex with the general formula [MoTp*(NO)I(X)], where Tp* =tris(3,5-dimethylpyrazolyl)hidroborate and X =1,4-bis(pyridin-4-ylethynyl)benzene) was found to exhibit the required chemical and physical properties as a photosensitiser in photoelectrochemical cell. The complex was structurally characterised by infrared, UV-Vis and electrochemical analysis. TiO₂ electrode films were prepared by paste technique and characterised by SEM and XRD. Photoelectrochemical properties of [MoTp*(NO)I(X)]-sensitisedTiO₂ photoelectrode were carried out in 1.0 M NaOH electrolyte with a SCE reference electrode and a platinum counter electrode. The [MoTp*(NO)I(X)]-sensitised TiO₂ photoelectrode showed positive photoinduced current compared to unsensitised TiO₂ photoelectrode.

Abstract: Bacterial are highly transmitted in our environment and have been identified as a primary contributor to the problem of indoor air quality and consequently lead to the illness of the occupants. Recently, nanotechnology represents an innovative approach to develop new formulations based on metallic nanoparticles with antimicrobial properties. TiO₂ has great promise to diminish bacterial activity. Antimicrobial activity of TiO₂and Ag-TiO₂ nanoparticles against Escherichia coli was examined in this study. TiO₂ nanoparticles with various silver contents were synthesized by sol gel method to produce uniform size, unagglomerated state and homogeneous nanoparticles. The nanoparticles were characterized by X-Ray diffraction (XRD) and transmittance electron microscopy (TEM). The effects of different silver concentration were studied using cotton diffusion test under fluorescence light irradiation. 0.06 mol % Ag-TiO₂ revealed best antibacterial activity. 0.06 mol % Ag-TiO₂ have antibacterial inhibition zone of 38 mm at the concentration of 2.0 M against E. coli. Swab test bacterial counts on left palm, tile, mouse pad and cotton have been tested before and after spraying with 0.06 mol % Ag-TiO₂. It showed that the bacterial count decreased for entire samples. The significant enhancement in the antibacterial properties of Ag-TiO₂ nanoparticles under visiblelight irradiation is related to the effect of noble metal Ag by acting as electron traps in TiO₂ band gap. The phase structure, crystallite size and crystallinity of TiO₂ also play an important role inantibacterial activity. The killing mechanism of Ag-TiO₂ undervisible light irradiation antibacterial activity over Ag-TiO₂nanoparticles was proposed based on our observations.

Abstract: Ruthenium (Ru)-II complexes such as the Ruthenium-tris(4,7-diphenyl-1,10-phenanthroline)dichloride (Ru(dpp)₃²⁺) is commonly used for dissolved oxygen sensing because of their profound advantages such as visible absorption, a large Stokes’ shift, good fluorescence quantum yields, long excitation lifetimes and good oxygen quenching efficiency. In this study, we report on the absorption characteristics of (Ru(dpp)₃²⁺) when it is exposed to dissolved oxygen where the absorption was determined using ultraviolet-visible (UV-Vis) absorbance spectroscopy. The results show that by decreasing the concentration ofRu(ddp)₃²⁺, the absorbance remained constant at optical wavelength of 455nm while the intensity changes with the presence of dissolved oxygen. The sensitivity of detecting dissolved oxygen was proven to improve by increasing the amount of Ru(ddp)₃²⁺ used.

Abstract: Synthesis and characterization of Ga-doped ZnO nanodisk and the formation of nanodisk/nanorod hybrid morphologies on AlN/Si substrate by polymer assisted one-pothydrothermal process have been studied. The morphology and structural properties were determined by field emission scanning electron microscopy (FESEM) and X-ray diffraction techniques. FESEM images clearly confirm the pure nanodisk formation for Ga-ZnO(0.5) at optimized ZnO concentration and hybrid nanodisk/nanorod formation obtained for Ga-ZnO (0.2) at lower ZnO concentration. The pure Ga-ZnO (0.5) nanodisk on AlN/Si thin film substrate showed effective response and fast recovery time towards UV light sensing in dark condition compared to low concentration route preparedGa-ZnO (0.2)/AlN/Si sample.

Abstract: In the current work p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 powders synthesized by solid-state microwave route were used to fabricating thermally evaporated thin films. The micro-thermoelectric devices were composedof 20-pairs and 10-pairs p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 thin films on glass substrates. Overall size of the thin films thermoelectric generators which consist of 20-pairs and 10-pairs of legs connected by aluminumelectrodes were 23 mm×20 mm and 12 mm×10 mm, respectively. The 20-pairs p–n thermocouples in series device generated output maximum open-circuit voltage of 275.3 mV and a maximum output power up to 54.4 nW at temperature difference ∆T= 162 K, and 109.4 mV and 16.7 nW at ∆T=162 K, for 10-pairs, respectively.

Abstract: Nanosilica powder produced from rice husk ash (RHA) via NaOH treatment has particle size in the range of 10-20 nm as revealed by transmission electron microscopy (TEM). The inhibitive action of nanosilicate from RHA on the corrosion of carbon steel SAE1045 in 0.5M HCl solution was studied using weight loss and potentio dynamic polarization methods. Result shows that the inhibition efficiency was increased with increasing of the inhibitor concentration. Nanosilicate was tremendously effective on carbon steel; exhibiting high inhibition efficiency attained 99%at optimum concentration of 175 ppm. Pitting was not observed on surface of carbon steel when the inhibitor was present. This finding was confirmed from surface morphology by scanning electron microscopy (SEM).