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Compounds and composites with high dielectric performance are in high demand in electronic industry due to their ability to store more charge and lower energy dissipation. In this paper we present synthesis of flexible three phase nanocomposite films of graphene/titania/polydimethylsiloxane with reasonably high real part of permittivity and very low imaginary part of permittivity. Dielectric permittivity of polydimethylsiloxane was raised by addition of graphene and rutile titania used as conducting and ceramic additives, respectively added in various weight ratios. Dielectric studies of synthesized three phase graphene/titania/polydimethylsiloxane nanocomposite films with weight/weight of 2:15:20 exhibits dielectric permittivity of 34.8 even at very high frequency of 2 MHz. While loss tangent of the same three phase graphene/titania/polydimethylsiloxane nanocomposite film is as low as 0.01 and its AC conductivity is 4.3 × 10⁻⁵ Sm⁻¹. Complex impedance and complex electric modulus of three phase graphene/titania/polydimethylsiloxane nanocomposite films also confirm its capacitive behaviour. Based on these properties and results we propose that these type of three phase graphene/titania/polydimethylsiloxane nanocomposite films can be used as useful dielectric materials in energy storage devices. Refereed/Peer-reviewed

Flexible electronics have gained eminent importance in recent years due to their high mechanical strength and resistance to environmental conditions, along with their effective energy storage and energy generating abilities. In this work, graphene/ceramic/polymer based flexible dielectric nanocomposites have been prepared and their dielectric properties were characterized. The composite was formulated by combining graphene with rutile and anatase titania, and polyvinylidene fluoride in different weight ratios to achieve optimized dielectric properties and flexibility. After preparation, composites were characterized for their morphologies, structures, functional groups, thermal stability and dielectric characterizations by using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis and impedance spectroscopy. Dielectric results showed that prepared flexible composite exhibited dielectric constant of 70.4 with minor leakage current (tan&delta, ) i.e., 0.39 at 100 Hz. These results were further confirmed by calculating alternating current (AC) conductivity and electric modulus which ensured that prepared material is efficient dielectric material which may be employed in electronic industry for development of next generation flexible energy storage devices.

Heavy metals contamination in the natural waters remains an unresolved environmental challenge pressing for the development of purification technologies. This paper presents the green engineering of a new bio-sponge for heavy metals adsorption composed of alginate bio-polymeric network encapsulated with reduced graphene oxide (rGO) modified with iron oxide nanoparticles and covalently attached multithiol (pentaerythritol tetrakis-mercaptopropionate) molecules using photoinitiated thiol-ene click chemistry. The multithiol functionalized graphene bio-sponge (SH-Graphene bio-sponge) is designed to enhance adsorption performances of heavy metals including structural approach combined with oxygen functionalities and high density of sulfur-containing groups (10.2 at % S, confirmed by X-ray Photoelectron Spectroscopy, XPS) with high binding affinity towards specific heavy metals (Cd and Pb). It was shown that the level of thiol functionalization on the graphene structure within the bio-sponge can be controlled by tuning the Ultraviolet (UV) irradiation time without adjusting the concentration of the precursors. SH-functionalized graphene bio-sponge showed outstanding adsorption capacity for Pb (II): 101.01 mg/g and Cd (II): 102.99 mg/g, outperformed commercial and literature reported adsorbents in highly competitive selectivity studies using co-existing heavy metal ions (Cu, Co, Pb and Cd) spiked- sea water. The multithiol modified bio-sponge also showcased an excellent stability and reusability feature with only 0.015 mg/L Pb (II) detected, conforming the strict United States Environmental Protection Agency (US EPA) maximum contaminant level (MCL) for lead, after five recurring cycles using mixed heavy metal ions solution and acidic eluent. The outcomes from this work present valuable and promising contribution towards the development of a scalable and sustainable adsorbents for efficient remediation of heavy metals from waters Refereed/Peer-reviewed

Refereed/Peer-reviewed In the present paper, synthesis and characterizations of flexible dielectric and ferroelectric polymer films combining different ratios of graphene, barium titanate and polydimethylsiloxane are presented. Broad range of characterization techniques were carried out to confirm their, morphological, structural, chemical, thermal and mechanical (flexibility, stretching, bending and twisting) characteristics. Dielectric studies showed that a high dielectric constant of the nanocomposite was dependent on the ratio of graphene:bariumtitanate:polydimethylsiloxane, showing that ratio of 15:25:100 had a high dielectric constant at high frequency range and the ratio 15:30:100 at the low frequency range. At 2 Hz the ratio 15:30:100 showed a dielectric constant of 116.9 which decreased to 30.6 at 2 MHz, thus showing capacitive nature at full frequency range. Meanwhile dielectric loss was very low i.e., 1.3 at 20 Hz and 0.02 at 2 MHz and AC conductivity was 1.6 × 10−7 S/m. Ferroelectric properties like energy density, energy loss and efficiency were calculated and compared. At an electric field of 0.92 kV/cm, remanant polarization and coercive field were 3.9 × 10−4 μC/cm2 and15.82 kV/cm, respectively. Energy density of 0.64 J/m3, energy loss 0.358 J/m3 and efficiency 64.2% were confirmed respectively. Results indicate that the nanocomposite films having desirable performances such as flexibility, thermal stability, high dielectric constant, high energy density are good candidates to be considered in energy storage and memory device applications.

A new method based on scanning atmospheric plasma for an ultrafast reduction of graphene oxide (GO) and preparation of highly conductive graphene films and patterns is presented. This simple method is shown to provide a direct and scalable fabrication of graphene films on flexible and shaped substrates with a variety of patterns for broad applications. An effective and ultrafast (similar to 60 s) reduction of GO films into highly conductive graphene films at room temperature is demonstrated by this process that is impossible to achieve by conventional wet chemical and thermal reduction process. The software controlled x-y scanning unit allows fabrication of graphene films with variety of patterns on different substrates including glass, plastic, ceramics and metals with complex shapes required for flexible and wearable electronics and devices. Characterization results confirmed that a thin transparent graphene film can be produced with a surface sheets resistance of 22 k Omega/sq at the transparency of 88%, and a thick film (similar to 25 mu m) with a sheet resistance of 186 Omega/sq. A practical application of plasma fabricated graphene films was demonstrated for a supercapacitor devices able to deliver an outstanding volumetric capacitance of 536.55 F/cm(3) at a current density of 1 A/g. (C) 2017 Elsevier Ltd. All rights reserved. Refereed/Peer-reviewed

Supercapacitors (SCs) due to their high energy density, fast charge storage and energy transfer, long charge discharge curves and low costs are very attractive for designing new generation of energy storage devices. In this work we present a simple and scalable synthetic approach to engineer ternary composite as electrode material based on combination of graphene with doped metal oxides (iron oxide) and conductive polymer (polypyrrole) with aims to achieve supercapacitors with very high gravimetric and areal capacitances. In the first step a binary composite with graphene mixed with doped iron oxide (rGO/MeFe2O4) (Me = Mn, Ni) was synthesized using new single step process with NaOH acting as a coprecipitation and GO reducing agent. This rGO/MnFe2O4 composite electrode showed gravimetric capacitance of 147 Fg−1 and areal capacitance of 232 mFcm−2 at scan rate of 5 mVs−1. In the final step a conductive polypyrrole was included to prepare a ternary composite graphene/metal doped iron oxide/polypyrrole (rGO/MnFe2O4/Ppy) electrode. Ternary composite electrode showed significantly improved gravimetric capacitance and areal capacitance of 232 Fg−1 and 395 mFcm−2 respectively indicating synergistic impact of Ppy additives. The method is promising to fabricate advanced electrode materials for high performing supercapacitors combining graphene, doped iron oxide and conductive polymers.

usc It is a challenge to compound hydrophilic MXene nanosheets with hydrophobic elastomers for various applications such as stretchable devices. In this work, Ti3C2Tx MXene nanosheets of 3.5 ± 1.0 nm in thickness were chemically modified by a facile method to enhance compatibility with a common elastomer, nitrile butadiene rubber (NBR). X-ray photoelectron spectroscopy showed the presence of nitrogen in the MXene through the modification by allylamine, whilst Raman spectroscopy revealed an increase in =O groups, exposing more reactive sites on the nanosheet surface. Fourier transform infrared spectroscopy indicated the disappearance of –C=C bonds in the nanocomposites as well as the breakage of –C≡N bonds, confirming that allylamine bridged MXene nanosheets with the matrix molecules. X-ray diffraction study showed the complete exfoliation of nanosheets in the elastomer matrix at 2.0 vol%, as confirmed by TEM micrographs. At 14.0 vol% MXene, the Young’s modulus, tensile strength and thermal conductivity of NBR were improved by 700, 240 and 440%, respectively. A percolation threshold of electrical conductivity was obtained at 3.9 vol% of MXene while thermal conductivity at 19.6 vol% – 1.01 W·m−1K−1 – outperformed previous elastomer nanocomposites containing boron nitride, zinc oxide, graphene nanoplatelets and alumina. Refereed/Peer-reviewed

Refereed/Peer-reviewed The inconsistent wettability of biological superwetting materials, due to aging, morphological change, structural fragility and biodegradation, limit their practical use for highly demanding applications such as oil-water separation and dye adsorption. Herein, we present a new source of superwetting materials harvested from waste chestnut-shell. The material is in the form of micro-fibres which are intrinsically oleophilic/hydrophobic, chemically stable, lightweight and structurally robust. The harvested microfibres, laying between inner-liner and outer shell of the chestnut, are naturally enriched with aliphatic and aromatic hydrocarbon that results in their high oleophilicity. We demonstrated that these superoleophilic fibre-networks could be used as oil-absorbent exhibiting outstanding absorption efficiency with a maximum capacity of similar to 94% of their own weight. Afterwards, an efficient filtration membrane was engineered using these micro-fibres showing their ability for continuous oil-water separation process for a series of organic solvents (toluene, canola oil, engine oil, hexane, turpentine oil, petrol and olive oil) co-existing with water. Furthermore, the fibres were realized to be capable of adsorbing organic dyes at oil-water interfaces in both static (slow adsorption) and dynamic (instant adsorption) condition suggesting their multifunctionality in wastewater treatments. A small amount of fibres (0.75 g/L) could efficiently remove water miscible dyes of lthodamine-B and Methylene blue with a maximum removal efficiency of 88% and similar to 91%, respectively. These low-cost natural fibres from biowaste with outstanding oil-water separation and organic dye-adsorption capacity have considerable advantages compared to other low-cost materials reported earlier for industrial wastewater-treatment and environmental remediation.

A novel porous 3D-structured carbon composite material with a unique architecture by combining graphene and carbonized metal-organic framework (C-MOF) (HKUST-1) microrods for high performing supercapacitors has been synthesised and characterised. The HKUST-1 microrods were prepared by a new method, converting their diamond-like shape into microrods via mechanical shear mixing in an aqueous solution. Grinding of HKUST-1 and graphene oxide (GO) resulted in the formation of a 3D GO-MOF composite with intercalated HKUST-1 microrods between GO sheets. The composite film was treated by a laser scribing method and created a highly porous, a high surface area (>600 m²/g) and conductive 3D nanostructured composite film (L-rGO-C-MOF) used as electrodes for supercapacitor applications. The prepared film showed a high capacitance of 390 F/g at 5 mV/s, and a cyclic stability of 97.8% at 10 A/g after 5000 cycles. The symmetrical supercapacitor delivered an excellent power density of 8037.5 W/kg with an outstanding energy density of 22.3 Wh/kg confirming a new pathway to design new 3D porous graphene-MOF composites for high-performance energy storage devices. Refereed/Peer-reviewed

To address the limitations of piezoelectric polymers which have a low dielectric constant andto improve their dielectric and ferroelectric efficiency for energy storage applications, we designed and characterized a new hybrid composite that contains polyvinylidene fluoride as a dielectric polymer matrix combined with graphene platelets as a conductive and barium titanite as ceramic ferroelectric fillers. Different graphene/barium titanate/polyvinylidene fluoride nanocomposite films were synthesized by changing the concentration of graphene and barium titanate to explore the impact of each component and their potential synergetic effect on dielectric and ferroelectric properties of the composite. Results showed that with an increase in the barium titanate fraction, dielectric efficiency ofthe nanocomposite was improved. Among all synthesized nanocomposite films, graphene/barium titanate/polyvinylidene fluoride nanocomposite in the weight ratio of 0.15:0.5:1 exhibited thehighest dielectric constant of 199 at 40 Hz, i.e., 15 fold greater than that of neat polyvinylidene fluoride film at the same frequency, and possessed a low loss tangent of 0.6. However, AC conductivity and ferroelectric properties of graphene/barium titanate/polyvinylidene fluoride nanocomposite films were enhanced with an increase in the graphene weight fraction. Graphene/barium titanate/polyvinylidene fluoride nanocomposite films with a weight ratio of 0.2:0.1:1 possessed a high AC conductivity of 1.2 &times, 10&minus, 4 S/m at 40 Hz. While remanent polarization, coercive field, and loop area of the same sample were 0.9 &mu, C/cm2, 9.78 kV/cm, and 24.5 &mu, C/cm2&middot, V, respectively. Our results showed that a combination of graphene and ferroelectric ceramic additives are an excellent approach to significantly advance the performance of dielectric and ferroelectric properties of piezoelectric polymers for broad applications including energy storage.

In comparison with inorganic and dry polymeric materials, conductive polymer hydrogels are promising soft electrode materials due to their unique solid-liquid interface. Nevertheless, the existing hydrogels lack either excellent electrochemical performance or mechanical resilience. Here we report a strategy to overcome this limitation by integrating two types of conducting polymers – polyaniline and PEDOT – through a molecular bridge provided by phytic acid. The acid replaces some of PSS, promoting transformation of PEDOT chains from the benzoic structure to the quinoid structure. The resulting hydrogel consists of a 3D network of PEDOT sheets where PANi are inlaid; it has highly improved mechanical properties in comparison with PEDOT hydrogel due to molecular interactions between PANi and PEDOT. A flexible solid-state supercapacitor based on PEDOT/PANi hydrogel delivered a high volumetric energy density of 0.25 mWh cm−3 at a power density of 107.14 mW cm−3, surpassing many of previously reported solid-state supercapacitors based on PEDOT and hydrogels of other conducting polymers and graphene oxide. This study represents a new direction for the development of conductive polymer composite hydrogels which combine excellent electrochemical performance with mechanical resilience Refereed/Peer-reviewed

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)., Rapid depletion of fossil fuel and increased energy demand has initiated a need for an alternative energy source to cater for the growing energy demand. Fuel cells are an enabling technology for the conversion of sustainable energy carriers (e.g., renewable hydrogen or bio-gas) into electrical power and heat. However, the hazardous raw materials and complicated experimental procedures used to produce electro-catalysts for the oxygen reduction reaction (ORR) in fuel cells has been a concern for the effective implementation of these catalysts. Therefore, environmentally friendly and low-cost oxygen reduction electro-catalysts synthesised from natural products are considered as an attractive alternative to currently used synthetic materials involving hazardous chemicals and waste. Herein, we describe a unique integrated oxygen reduction three-dimensional composite catalyst containing both nitrogen-doped carbon fibers (N-CF) and carbon microspheres (N-CMS) synthesised from apricot sap from an apricot tree. The synthesis was carried out via three-step process, including apricot sap resin preparation, hydrothermal treatment, and pyrolysis with a nitrogen precursor. The nitrogen-doped electro-catalysts synthesised were characterised by SEM, TEM, XRD, Raman, and BET techniques followed by electro-chemical testing for ORR catalysis activity. The obtained catalyst material shows high catalytic activity for ORR in the basic medium by facilitating the reaction via a four-electron transfer mechanism., The authors are thankful for the support of the Australian Solar Thermal Research Initiative (ASTRI), ARC Hub for Graphene Enabled Industry Transformation (IH 150100003), the University of Adelaide, School of Chemical Engineering and School of Chemistry. The technical support provided by Adelaide Microscopy and the Micro Analysis Research Facility at Flinders Microscopy (Flinders University) was greatly appreciated.

In this report, we employed surface-initiated atom transfer radical polymerisation to graft thermo-responsive copolymers of oligo(ethylene glycol) methacrylates from the surface of diatom biosilica microcapsules. We demonstrate the application of the resulting composites for thermo-responsive drug delivery Refereed/Peer-reviewed

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)., The synthesis and properties of an oxygen reduction catalyst based on a unique 3-dimensional (3D) nitrogen doped (N-doped) carbon composite are described. The composite material is synthesised via a two-step hydrothermal and pyrolysis method using bio-source low-cost materials of galactose and melamine. Firstly, the use of iron salts and galactose to hydrothermally produceiron oxide (Fe2O3) magnetic nanoparticle clusters embedded carbon spheres. Secondly, magnetic nanoparticles diffused out of the carbon sphere when pyrolysed in the presence of melamine as nitrogen precursor. Interestingly, many of these nanoparticles, as catalyst-grown carbon nanotubes (CNTs), resulted in the formation of N-doped CNTs and N-doped carbon spheres under the decomposition of carbon and a nitrogen environment. The composite material consists of integrated N-doped carbon microspheres and CNTs show high ORR activity through a predominantly four-electron pathway.

Anodic aluminium oxide (AAO) has been investigated and utilized in numerous products for almost a century. But the rapidly increasing interest in nanoscale materials and their outstanding properties has propelled nanoporous AAO to the fore as one of the most popular nanomaterial with applications across a gamut of areas including molecular separation, catalysis, energy generation and storage, electronics and photonics, sensors and biosensors, drug delivery and template synthesis. Material fabrication of AAO is based on facile and inexpensive electrochemical anodization with the self-ordering process of nanopores not requiring any lithography or templating, and the outcome of the process are perfectly ordered and size controlled nanopores with distinctive pore geometries. Recent research on AAO is characterized by a remarkable trajectory of innovation, in particular with regards to control of surface functionality and, concomitantly, to the design of intricate structural features such as modulated, branched, and multilayered pore architectures. This review illuminates research on recent development of AAO focussing on surface and structural engineering, and on emerging applications. Key examples and critical preparative issues and resulting improvements sparking opportunities for further applications in AAO properties are discussed. We conclude this review with an outlook providing a critical perspective on future trends on surface and structural engineering of AAO. Refereed/Peer-reviewed

The conversion of titania (TiO2) nanotubes into titanium (Ti), while preserving their nanotubular structures, is demonstrated. Their application as bone implants and electrodes for combined local drug delivery and electrical stimulation therapy is proposed. Refereed/Peer-reviewed

This work presents the fabrication of gold nanotube membranes (GNT) using gold deposition on porous anodic aluminum oxide (AAO) template and demonstrates the catalytic properties generated by the nanostructured gold surface. AAO membranes were prepared by electrochemical anodization of Al in 0.3 M oxalic acid electrolyte. Electroless gold deposition on AAO was performed via several steps using commercially available gold plating solutions. Scanning electron microscopy (SEM) images confirm that the gold nanotubes formed inside AAO pores have characteristic nanoclustered morphology as a result of the nucleation process during gold deposition. It was found that catalytic properties of GNT membranes depend on the size of gold nanoclusters which can be controlled by pH during nucleation process. The excellent catalytic properties (catalytic rate constant k = 0.132 min−1) of the GNT membranes were demonstrated by testing catalytic conversion of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) in the presence of NaBH4 as a reductant. The correlation between the size of gold nanoclusters and catalytic activity was verified showing the capability of controlling and further improving catalytic properties of GNT membranes. Refereed/Peer-reviewed

Naturally available and biocompatible materials are potential substitutes for synthetic mesoporous materials as suitable drug carriers for the development of cost-effective drug delivery systems. This work investigates the application of a porous silica material derived from diatoms, also known as diatomaceous earth. The aim is to explore the surface functionalization of diatom microcapsules and their impact on the drug loading and release characteristics of water-insoluble drugs. Indomethacin was used as the model for poorly soluble drug. The surface modification on diatoms was performed with two organosilanes; 3-aminopropyltriethoxy silane and N-(3-(trimethoxysilyl) propyl) ethylene diamine and phosphonic acids (2-carboxyethyl-phosphonic acid and 16-phosphono-hexadecanoic acid) providing organic surface hydrophilic and hydrophobic properties. Extensive characterizations using scanning electron microscopy, X-ray photoelectron spectroscopy and differential scanning calorimetry was performed to confirm covalent grafting of monolayer aminosilane and phosphonic acid on the diatom surfaces. Differences in loading capacity of diatoms (15–24%) and release time (6–15 days) were observed which is due to the presence of different functional groups on the surface. It was found that 2-carboxyethyl-phosphonic acid, 3-aminopropyltriethoxy silane and N-(3-(trimethoxysilyl) propyl) ethylene diamine render diatom surfaces hydrophilic, due to polar carboxyl functional group (COOH) and active amine species (NH and NH2) that favor drug adsorption; better encapsulation efficiency and prolonged release of drugs, over the hydrophobic surface created by 16-phosphono-hexadecanoic acid. This work demonstrates diatom porous silica as a promising drug carrier, with possibility to further improve their performances by tailoring their surface functionalities to achieve the required drug loading and release characteristics for different therapeutic conditions.

Bacterial infection, extensive inflammation and poor osseointegration have been identified as the major reasons for [early] orthopaedic implant failures based on titanium. Creating implants with drug-eluting properties to locally deliver drugs is an appealing way to address some of these problems. To improve properties of titanium for orthopaedic applications, this study explored the modification of titanium surfaces with titaniananotube (TNT) arrays, and approach that combines drug delivery into bone and potentially improved bone integration. A titania layer with an array of nanotube structures (∼120 nm in diameter and 50 μm in length) was synthesized on titanium surfaces by electrochemical anodization and loaded with the water-insoluble anti-inflammatory drug indomethacin. A simple dip-coating process of polymer modification formed thin biocompatible polymer films over the drug-loaded TNTs to create TNTs with predictable drug release characteristics. Two biodegradable and antibacterial polymers, chitosan and poly(lactic-co-glycolic acid), were tested for their ability to extend the drug release time of TNTs and produce favourable bone cell adhesion properties. Dependent on polymer thickness, a significant improvement in the drug release characteristics was demonstrated, with reduced burst release (from 77% to >20%) and extended overall release from 4 days to more than 30 days. Excellent osteoblast adhesion and cell proliferation on polymer-coated TNTs compared with uncoated TNTs were also observed. These results suggest that polymer-modified implants with a TNT layer are capable of delivering a drug to a bone site over an extended period and with predictable kinetics. In addition, favourable bone cell adhesion suggests that such an implant would have good biocompatibility. The described approach is broadly applicable to a wide range of drugs and implants currently used in orthopaedic practice. Refereed/Peer-reviewed

Diatom silica microparticles from natural diatomaceous earth (DE) silica have been functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) and their application for adsorption of gold (III) ions from aqueous solutions is demonstrated. Fourier transform infrared spectroscopy (FTIR) and X-ray Photoelectron spectroscopy (XPS) analyses of the MPTMS modified diatom microparticles revealed that the silane layer with functional group (-SH) was successfully introduced to the diatom surface. The adsorption study of Au(III) ions using MPTMS-DE indicated that the process depends on initial gold (III) concentration and pH showing maximum adsorption capacity at pH = 3. The Au(III) adsorption kinetics results showed that the adsorption was very fast and followed a pseudo-second-order reaction model. The Langmuir model was used to provide a sound mechanistic basis for the theoretical of the adsorption equilibrium data. Gold recovery from MPTMS-DE structures was also investigated by using acidified thiourea solution and found to be high (> 95%). These results show that chemically modified DE microparticles can be used as a new, cost effective and environmentally benign adsorbent suitable for adsorption of gold metal ions from aqueous solutions. Refereed/Peer-reviewed

Aim: This study explores the use of natural silica-based porous material from diatoms, known as diatomaceous earth, as a drug carrier of therapeutics for implant- and oral-delivery applications. Materials & Methods: To prove this concept, two drugs models were used and investigated: a hydrophobic (indomethacin) and hydrophilic (gentamicin). Results & Discussion: Results show the effectiveness of diatom microcapsules for drug-delivery application, showing 14–22 wt% drug loading capacity and sustained drug release over 2 weeks. Two steps in the drug release from diatom structures were observed: the first, rapid release (over 6 h is attributed to the surface deposited drug) and the second, slow and sustained release over 2 weeks with zero order kinetics. Conclusion: These results confirm that natural material based on diatom silica can be successfully applied as a drug carrier for both oral and implant drug-delivery applications, offering considerable potential to replace existing synthetic nanomaterials.

In this review article we collect and analyse preparation, chemistry and properties of silica materials relevant for drug delivery applications. We review some of the most relevant milestones in the research of silica materials for implantable, oral, intravenous and dermal drug delivery systems. Preparation, chemistry and drug delivery characteristics of fumed silica nanoparticles (oral and dermal delivery route), silica xerogels (implant delivery), mesoporous silica materials (implant and oral delivery) and mesoporous silica spheres (intravenous delivery) with particular emphasis on their role in anticancer therapy and the design of stimuli responsive drug delivery systems are analysed. Recent progress in the research of silica materials for controlled drug delivery, namely, biocompatibility aspects, research on hybrid materials, anticancer and stimuli-responsive mesoporous silica materials are particularly emphasized. Refereed/Peer-reviewed

Carbon nanotubes are attractive approach for designing of new membranes for advanced molecular separation because of their unique transport properties and ability to mimic biological protein channels. In this work the synthetic approach for fabrication of carbon nanotubes (CNTs) composite membranes is presented. The method is based on growth of multi walled carbon nanotubes (MWCNT) using chemical vapour deposition (CVD) on the template of nanoporous alumina (PA) membranes. The influence of experimental conditions including carbon precursor, temperature, deposition time, and PA template on CNT growth process and quality of fabricated membranes was investigated. The synthesis of CNT/PA composites with controllable nanotube dimensions such as diameters (30-150 nm), and thickness (5-100 μm), was demonstrated. The chemical composition and morphological characteristics of fabricated CNT/PA composite membranes were investigated by various characterisation techniques including scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM) and x-ray diffraction (XRD). Transport properties of prepared membranes were explored by diffusion of dye (Rose Bengal) used as model of hydrophilic transport molecule. Refereed/Peer-reviewed

Transition metal hexacyanoferrate (MeHCF) have attracted extensive attention because of their outstanding properties including, electrocatalysis, molecular magnetism, biosensing and ion-exchange. This paper describes an approach for fabrication of ordered nanoarrays of Ni hexacyanoferrate (NiHCF) structures with different morphologies such as dots, rods and tubes in order to advance their properties and applications. The method is based on the conversion of Ni into NiHCF nanostructures by electrochemical oxidation in the presence of hexacyanoferrate ions, using nanoporous anodic alumina oxide (AAO) as a template. The structure and morphology of formed Ni and NiHCF nanoarrays were confirmed by scanning electron microscopy (SEM), showing agreement with the pore structures of the AAO template. The electrocatalytic activity of NiHCF nanorod array electrodes showed high catalytic properties for the detection of hydrogen peroxide and the potential to be used as a platform for direct biosensing applications. The ion-exchange ability of fabricated NiHCF nanostructures (nanorods and nanotubes) toward alkali cations such as Na + has been successfully confirmed.

The fabrication of microstructured surfaces using biological tem- plates was investigated with the aim of exploring of a facile and low cost approach for the fabrication of structured surfaces with superhydrophobic properties. Two soft lithographic techniques, i.e., replica moulding and nano-imprinting, were used to replicate the surfaces of a biological substrate. Leaves of the Agave plant (Agave attenuate), a cost-free biological template, were used as a model of a biosurface with superhydrophobic properties. The replication process was performed using two polymers: an elastomeric polymer, poly(dimethylsiloxane) (PDMS), and a polyurethane (PU) based, UV-curable polymer (NOA 60). In the first replication step, negative polymer replicas of the surface of leaves were fabricated, which were used as masters to fabricate positive polymer replicas by moulding and soft imprinting. The pattern with micro and nanostructures of the surface of the leaf possesses superhydrophobic properties, which was successfully replicated into both polymers. Finally, the positive replicas were coated with a thin gold film and modified with self-assembled monolayers (SAMs) to verify the importance of the surface chemistry on the hydrophobic properties of the fabricated structures. Wetting (contact angle) and structural (light microscopy and scanning electron microscopy) characterization was performed to confirm the hydrophobic properties of the fabricated surfaces (>150°), as well as the precision and reproducibility of the replication process. Refereed/Peer-reviewed

Here, we report on the development of advanced biopolymer-coated drug-releasing implants based on titanium (Ti) featuring titania nanotubes (TNTs) on its surface. These TNT arrays were fabricated on the Ti surface by electrochemical anodization, followed by the loading and release of a model antibiotic drug, gentamicin. The osteoblastic adhesion and antibacterial properties of these TNT–Ti samples are significantly improved by loading antibacterial payloads inside the nanotubes and modifying their surface with two biopolymer coatings (PLGA and chitosan). The improved osteoblast adhesion and antibacterial properties of these drug-releasing TNT–Ti samples are confirmed by the adhesion and proliferation studies of osteoblasts and model Gram-positive bacteria (Staphylococcus epidermidis). The adhesion of these cells on TNT–Ti samples is monitored by fluorescence and scanning electron microscopies. Results reveal the ability of these biopolymer-coated drug-releasing TNT–Ti substrates to promote osteoblast adhesion and proliferation, while effectively preventing bacterial colonization by impeding their proliferation and biofilm formation. The proposed approach could overcome inherent problems associated with bacterial infections on Ti-based implants, simultaneously enabling the development of orthopedic implants with enhanced and synergistic antibacterial functionalities and bone cell promotion.

A new method mapping the defects in self-assembled monolayers (SAMs) is described. The method is based on electrochemical polymerisation of nonconductive tyramine in defect sites of a monolayer and subsequent visualisation of the polymer structures by atomic force microscopy (AFM). SAMs of hexadecanthiol (HDT) on gold prepared by deposition from solution and microcontact printing were used as a model for this study. The method allows easy mapping of defects on monolayers and provides information about their shape, size, size distribution, defect density and spatial distribution. Comparative electrochemical characterisation of defects in SAMs before and after polymerisation shows that polymer growth occurs on the sites of uncovered gold. The approach should be applicable for the characterisation of defects in other types of ultra-thin organic films on conducting surfaces.

Alzheimer's disease (AD) is caused by the accumulation of β-amyloid protein (Aβ) in the brain. The aggregation of β-amyloid protein to higher molecular weight fibrillar forms is also considered to be an important step in the pathogenesis of the disease. the memory problems associated with AD are likely to be caused by changes in synaptic plasticity. Recent studies suggest that Aβ binds to the α7 nicotinic acetylcholine receptor (α7 nAChR), which plays an important role in synaptic plasticity and memory. A loop domain localized towards the C-terminus of the extracellular region of the receptor has been identified as forming part of a putative Aβ-binding site. In cell culture experiments, the binding of Aβ to the α7 nAChR has been found to cause an increase in the level of acetylcholinesterase, which is also increased around amyloid plaques in the AD brain. These studies indicate that the Aβ-binding site on the α7 nAChR receptor is an important new target for therapeutic development in AD.

The reversible cyclic voltammetry of pea plastocyanin ( Pisum sativum ) was studied with a wide range of electrodes: edge-oriented pyrolytic graphite (PGE), glassy carbon (GCE), gold (Au) and platinum (Pt) electrodes. Plastocyanin was coated onto the electrode surface by exploiting the electrostatic interaction between the negatively charged protein and a wide range of positively charged promoters. The effect of the redox response with an extended range of promoters, including poly- l -lysine, polymyxin B, neomycin, tobramycin, geneticin, spermine and spermidine, were included in this study. The resulting cyclic voltammograms reveal that the observed midpoint potential for plastocyanin can be shifted significantly depending on the choice of promoter. The stability of the negatively charged plastocyanin–promoter layer on an electrode was gauged by the rate of bulk diffusion of the protein from the immobilised film into the solution. Reversible cyclic voltammograms were obtained using edge-oriented pyrolytic graphite (PGE) and glassy carbon electrodes (GCE) with all promoters; however, platinum and gold electrodes were unable to sustain a defined redox response. The combination of pyrolytic graphite electrode/poly- l -lysine/plastocyanin was found to be the most stable combination, with a redox response which remained well defined in solution for more than 1 h at pH 7.0. The midpoint potentials obtained in this manner differed between the two graphite electrodes PGE and GCE using poly- l -lysine as the promoter. This effect was in addition to the expected pH dependence of the midpoint potential for plastocyanin and the results indicated that the p K a for plastocyanin on PGE was 4.94 compared to that on GCE of 4.66. It is concluded that both the electrode material and the nature of the promoter can influence the position of the redox potentials for proteins measured in vitro. This study extends the range of biogenic promoters used in combination with electrode materials. Thus, we can begin to develop a more comprehensive understanding of electrode–protein interactions and draw conclusions as to metalloprotein function, in vivo. To support these studies, we have sought information as to the nature of the electrode/promoter/protein interaction using scanning tunneling microscopy (STM) to study both the promoter and the plastocyanin protein on a gold surface.

Three immobilization methods have been used for scanning tunneling microscopy (STM) studies of glucose oxidase (GOD) on gold. They are based on (a) physical adsorption from solution, (b) microcontact printing, and (c) covalent bonding onto self-assembled monolayers (SAMs) of 3-mercaptopropionic acid (MPA). The STM images are used to provide information about the organization of individual GOD molecules and more densely packed monolayers of GOD on electrode surfaces, thus providing information on the role of interfacial structure on biosensor performance. The use of atomically flat gold substrates enables easy distinction of deposited enzyme features from the flat gold substrate. Microcontact printing is found to be a more reliable method than adsorption from solution for preparing individual GOD molecules on the gold surface. STM images of printed samples reveal two different shapes of native GOD molecules. One is a butterfly shape with dimensions of 10 ± 1 nm × 6 ± 1 nm, assigned to the lying position of...

In the quest for solutions to meeting future energy demands, solar fuels play an important role. A particularly promising example is photocatalysis since even incremental improvements in performance in this process are bound to translate into significant cost benefits. Here, we report that semiconducting and high surface area 3D silicon replicas prepared from abundantly available diatom fossils sustain photocurrents and enable solar energy conversion. Refereed/Peer-reviewed

We report the application of diatom as a solid carrier for water insoluble drugs applied in oral drug delivery system based on the self-emulsifying drug delivery system (SEDDS) caprylocaproyl macrogol-8 glycerides/lecithin/propylene glycol/caprylic/capric triglyceride. Diatoms are fossilized skeletons of photosynthetic algae with complex 3-dimensional (3D), porous structure consisting of amorphous silica, obtained by purification of diatomaceous earth. Different solid samples of carbamazepine (CBZ) suspension in SEDDS, called solid self-emulsifying phospholipid suspension (SSEPS), were prepared using two methods: adsorption of CBZ dispersion in SEDDS by gentle mixing with diatoms in mortar with pestle (Method A) or dispersion of diatoms in ethanol solution of CBZ and SEDDS components, followed by ethanol evaporation (Method B). Release rate of CBZ from SSEPS was significantly higher in comparison to pure drug, physical mixture of diatoms and CBZ as well as solid dispersion of pure CBZ and diatoms obtained by ethanol evaporation. The dissolution of CBZ from SSEPS sample prepared using method B was faster than from the sample prepared by the method A. Higher dissolution for sample prepared by the method B can be attributed to the partial adsorption (deeper localization) of liquid material inside the pores of diatoms. Upon storage of the samples under accelerated conditions (40 °C and 70% RH) for 10 weeks no significant changes in CBZ crystallinity and dissolution was in case of SSEPS, contrary to solid dispersion with increased crystallinity, indicating that diatoms with adsorbed liquid CBZ-loaded SEPS can maintain initial CBZ characteristics. Refereed/Peer-reviewed

Molecular or ion transport through a single nanopore or nanopore array is a key process in a number of applications including: molecular separation, biosensing, energy storage, nanofluidics and nanoelectronics. In this study, the electrochemical and electrical properties of nanopore arrays were investigated by electrochemical impedance spectroscopy (EIS), to explore their capability towards the development of improved nanopore biosensing devices. Anodic aluminum oxide (AAO) nanopore arrays with square patterns were fabricated by a photolithographic technique for use as a biosensing platform. To demonstrate the potential capability of these nanoporous arrays for biosensing applications, their internal surfaces were functionalized with a self-assembled monolayer of phosphonic acid; followed by covalent bonding with the model binding molecule streptavidin. The sensing performance of the prepared sensing device was characterized by EIS using different concentrations of biotin as probe molecule. The changes in impedance signal in response to the specific binding of biotin molecules to the streptavidin inside nanopores were monitored and explored depending on pore morphology. The results obtained for this system exhibit a high level of sensitivity and selectivity, which could provide the basis for the development of superior biosensing devices. Refereed/Peer-reviewed

The fabrication of enzyme electrodes using self-assembled monolayers (SAMs) has attracted considerable interest because of the spatial control over the enzyme immobilization. A model system of glucose oxidase covalently bound to a gold electrode modified with a SAM of 3-mercaptopropionic acid was investigated with regard to the effect of fabrication variables such as the surface topography of the underlying gold electrode, the conditions during covalent attachment of the enzyme and the buffer used. The resultant monolayer enzyme electrodes have excellent sensitivity and dynamic range which can easily be adjusted by controlling the amount of enzyme immobilized. The major drawback of such electrodes is the response which is limited by the kinetics of the enzyme rather than mass transport of substrates. Approaches to bringing such enzyme electrodes into the mass transport limiting regime by exploiting direct electron transfer between the enzyme and the electrode are outlined.

A multi-drug delivery system with sequential release based on titania nanotube arrays and polymer micelles as drug carriers is presented. Delivery of multiple water insoluble and soluble drugs required for combined local therapy is demonstrated. Refereed/Peer-reviewed

A study of reflective interference spectroscopy [RIfS] properties of nanoporous anodic aluminium oxide [AAO] with the aim to develop a reliable substrate for label-free optical biosensing is presented. The influence of structural parameters of AAO including pore diameters, inter-pore distance, pore length, and surface modification by deposition of Au, Ag, Cr, Pt, Ni, and TiO2 on the RIfS signal (Fabry-Perot fringe) was explored. AAO with controlled pore dimensions was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid at different voltages (30 to 70 V) and anodization times (10 to 60 min). Results show the strong influence of pore structures and surface modifications on the interference signal and indicate the importance of optimisation of AAO pore structures for RIfS sensing. The pore length/pore diameter aspect ratio of AAO was identified as a suitable parameter to tune interferometric properties of AAO. Finally, the application of AAO with optimised pore structures for sensing of a surface binding reaction of alkanethiols (mercaptoundecanoic acid) on gold surface is demonstrated. Refereed/Peer-reviewed

Stimulus-responsive drug delivery system using titania nanotube arrays loaded with polymer micelles as drug-carriers is presented. Amagnetic stimulated release of drug-carriers was achieved by activating magnetic nanoparticles loaded at the bottom of the nanotubes. Refereed/Peer-reviewed

In this report, a label-free reflectometric interference spectroscopy (RIfS) based microchip biosensor for the detection of circulating tumour cells (CTCs) is demonstrated. Highly ordered nanoporous anodic aluminium oxide (AAO) fabricated by electrochemical anodization of aluminium foil was used as the RIfS sensing platform. Biotinylated anti-EpCAM antibody that specifically binds to human cancer cells of epithelial origin such as pancreatic cancer cells (PANC-1) was covalently attached to the AAO surface through multiple surface functionalization steps. Whole blood or phosphate buffer saline spiked with low numbers of pancreatic cancer cells were successfully detected by specially designed microfluidic device incorporating an AAO RIfS sensor, without labour intensive fluorescence labelling and/or pre-enhancement process. Our results show that the developed device is capable of selectively detecting of cancer cells, within a concentrations range of 1000–100,000 cells/mL, with a detection limit of fewer than 1000 cells/mL, a response time of fewer than 5 min and sample volume of 50 μL of. The presented RIfS method shows considerable promise for translation to a rapid and cost-effective point-of-care diagnostic device for the detection of CTCs in patients with metastatic cancer. Refereed/Peer-reviewed

The concept of a microfluidic biosensing device based on reflective interferometric spectroscopy (RIfS) is presented in this article. The key element of the sensor is a highly ordered nanoporous structure of anodic aluminium oxide (AAO) integrated into a microfluidic chip combined with an optical fiber spectrophotometer. AAO was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid. The structural and geometrical features of the AAO porous structures were controlled to provide optimal RIfS sensing characteristics and there sensing capabilities were explored using two different strategies; i) detection based on the response generated by pefusion of analyte ions inside the pores and ii) detection based on specific adsorption of analyte molecules on surface of AAO pores. The second strategy is based on chemical modification of the AAO surface to target molecules based on specific surface binding reactions. In this work two cases are presented, including the binding of small thiol molecules on gold-modified AAO (Au-AAO) and binding of larger targets such as circulating tumour cells (CTC) on antibody-modified AAO. Our preliminary results show an excellent capability of our system in the detection of different analytes using both strategies, and confirm good potential for the development and application of interferometric label-free biosensing devices in a wide range of biomedical applications. Refereed/Peer-reviewed

In the past two decades, nanoscale advanced materials have been explored for biosensing molecules, so new horizons have opened up for identifying and quantifying biomolecules, and possible early diagnosis of diseases. DNA nanobiosensors show promise. This article provides an overview on their optical and electrochemical aspects. We discuss recent progress in this field, describing basic concepts of molecular beacons and quantum dots as optical nano-imaging systems. Also, carbon nanotubes provide a platform for development and advancement of electrochemical DNA nanobiosensors, which are increasingly being implemented as robust tools for detection in biomedical sciences. Refereed/Peer-reviewed

The design of a microfluidic nanoporous reflective interferometric (RIfS) sensor is presented. The key element of the sensor is a highly ordered nanoporous structure of anodic aluminium oxide (AAO) integrated into a microfluidic chip and combined with an optical fibre spectrophotometer and notebook computer. AAO with controlled pore dimensions was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid at 50V for 40 minutes. The performance of the microfluidic RIfS for sensing of surface binding reaction of alkanethiols (mercapto undecanoic acid) on gold is evaluated showing excellent sensitivity. The results show potential for development and application of interferometric label-free biosensing elements for a wide range of biomedical applications. Keywords: Reflective interferometric spectroscopy, Fabry-Perot fringes, microchip interference sensor, nanoporous alumina. Refereed/Peer-reviewed

Electroless deposition was used to coat porous alumina membranes with gold. This process reduced the pore diameters and provided a platform suitable for surface modifications with self assembled monolayers (SAMs). The surface enhanced Raman scattering (SERS) effect was employed in order to confirm and characterise the formation of SAMs of 3-mercaptobenzoic acid (mMBA) inside the pores of gold nanotube membranes prepared using porous alumina (PA) templates. The investigation of the coverage and reproducibility of SAMs within porous matrices is of utmost importance in the design of filtration membranes and sensing platforms. Raman spectroscopy is capable of spatially resolved techniques such as mapping which was used to characterise the distribution of mMBA assembly within the pores. Due to the highly ordered structure of porous alumina and well controlled electroless gold deposition, these gold coated membranes have the potential to develop into SERS active substrates for ultrasensitive sensing technologies. Refereed/Peer-reviewed

This Letter reports the use of nanoporous anodic aluminium oxide (AAO) for reflective interferometric gas sensing. Gas detection is based on changes of the interference signal from AAO porous layer as a result of the specific adsorption of gas molecules on a metal coated surface. Two different metal coatings – gold (Au) and platinum (Pt) – were used and their application for the detection of hydrogen sulphide (H2S) and hydrogen (H2) is shown. The practical application of a microchip Au-AAO sensor for measurement of H2S concentration and monitoring of malodour is also presented. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, we present recent work from our group focussed on the fabrication of nanopore and nanotube arrays using self-ordered electrochemistry, and their application in several key areas including template synthesis, molecular separation, optical sensing, and drug delivery. We have fabricated nanoporous anodic aluminium oxide (AAO) with controlled pore dimensions (20-200 nm) and shapes, and used them as templates for the preparation of gold nanorod/nanotube arrays and gold nanotube membranes with characteristic properties such as surface enhanced Raman scattering and selective molecular transport. The application of AAO nanopores as a sensing platform for reflective interferometric detection is demonstrated. Finally, a drug release study on fabricated titania nanotubes confirms their potential for implantable drug delivery applications. Refereed/Peer-reviewed

We report the fabrication of highly ordered TiO 2 nanotube arrays employing electrochemical anodization of titanium using an organic electrolyte comprised of water, NH 4 F , and ethylene glycol. To achieve the self-ordering regime of TiO 2 nanotube growth and reliable fabrication optimal potential window between 80 and 100 V was determined. We show that anodization voltage can be used not only to control nanotube diameters (70–180 nm) but also to have impact on nanotube growth rate. The anodization voltage and anodization time were used to adjust the length of TiO 2 nanotube (thickness of nanotube layer). TiO 2 nanotube array films and self-supporting layers with thickness from < 5 μm to > 250 μm were routinely fabricated.

This work presents template synthesis of ordered arrays of nickel, cobalt and nickel hexacyanoferrates (NiHCF) with several distinct morphologies such as dots, rods, and tubes. Anodic alumina oxide (AAO) with preferred pore diameters and thickness was fabricated by electrochemical anodization of aluminum used as template. Ni and Co nanostructures inside AAO template were prepared by electrodeposition using galvanostatic method. NiHCF nanostructures were prepared by electrochemical oxidation of Ni using cyclic voltametry (CV) in the presence of hexacyanoferrate ions. The morphology, chemical, and functional properties of prepared nanostructures were investigated by scanning electron microscopy (SEM), energydispersive X-ray microscopy (EDAX), and electrochemical methods. The electrocatalytic properties of NiHCF nanorod arrays electrode and their potential for the detection of hydrogen peroxide and biosensing application were demonstrated. Refereed/Peer-reviewed

Bacterial infections present an enormous problem causing human suffering and cost burdens to the healthcare systems worldwide. Herein we present several versatile strategies for controlled release of antibacterial agents which include silver ions as well as traditional antibiotics. At the heart of these release platforms is a thin film deposited by plasma polymerization. The use of plasma polymerization makes these strategies applicable to the surface of many types of medical devices since the technique for deposition of a polymer film from plasma in practically substrate independent. Refereed/Peer-reviewed

Diatom silica microcapsules prepared by purification of diatomaceous earth (DE) were functionalised by dopamine modified iron-oxide nanoparticles, in order to introduce diatoms with magnetic properties. The application of magnetised diatomsas magnetically guided drug delivery microcarriers has been demonstrated. Refereed/Peer-reviewed