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Layered silicate nanoparticles (LSN) are widely used in industrial applications and consumer products. They also have potential benefits in biomedical applications such as implantable devices and for drug delivery. To study how nanomaterials interact with cells and tissues, techniques to track and quantify their movement through different biological compartments are essential. While radiolabels can be very sensitive, particularly for in vivo studies, fluorescent labeling has been preferred in recent years because of the array of methods available to image and quantify fluorescent nanoparticles. However, labeling can be problematic, especially if it alters the physical properties of the nanomaterial. Herein is described a novel non-covalent labeling technique for LSN using readily available fluorescent dimeric cyanine dyes without the need to use excess amounts of dye to achieve labeling, or the need for removal of unbound dye. The approach utilizes the cationic binding properties of layered silicate clays and the multiple quaternary nitrogens associated with the dyes. Preparation of YOYO-1 labeled LSN with optimal dispersion in aqueous media is presented. The utilization of the labeled particles is then demonstrated in cell binding and uptake studies using flow cytometry and confocal microscopy. The labeled LSN are highly fluorescent, stable and exhibit identical physical properties with respect to the unlabeled nanoparticles. The general approach described here is applicable to other cyanine dyes and may be utilized more widely for labeling nanoparticles that comprise a crystalline plate structure with a high binding capacity.

While plasma proteins can influence the physicochemical properties of nanoparticles, the adsorption of protein to the surface of nanomaterials can also alter the structure and function of the protein. Here, we show that plasma proteins form a hard corona around synthetic layered silicate nanoparticles (LSN) and that one of the principle proteins is serum albumin. The protein corona was required for recognition of the nanoparticles by scavenger receptors, a major receptor family associated with the mononuclear phagocyte system (MPS). Albumin alone could direct nanoparticle uptake by human macrophages, which involved class A but not class B scavenger receptors. Upon binding to LSN, albumin unfolded to reveal a cryptic epitope that could also be exposed by heat denaturation. This work provides an understanding of how albumin, and possibly other proteins, can promote nanomaterial recognition by the MPS without albumin requiring chemical modification for scavenger receptor recognition. These findings also demonstrate an additional function for albumin in vivo.

Carboxyl-functionalized multiwalled carbon nanotubes (MWCNTs) have been successfully radiolabelled with cobalt-57 (57Co) (T1/2 = 270 days) via the attachment of the bifunctional caged ligand MeAMN3S3sar. In this study MeAMN3S3sar has been synthesized and coupled to MWCNTs to form the conjugate MWCNT–MeAMN3S3sar. Synthesis was confirmed with nuclear magnetic resonance. X-ray photoelectron spectroscopy (XPS) confirmed the conjugation. Non-radioactive labelling of this conjugate was completed with Cu(II) ions to confirm the stability of the MeAMN3S3sar after coupling with the MWCNTs. The complexation of the Cu(II) was also confirmed with XPS. Transmission electron microscopy was used to demonstrate that the coupling reaction had a negligible effect on the size and shape of the MWCNTs. Radiolabelling of the MWCNT–MeAMN3S3sar conjugate and pristine (untreated) MWCNTs (non-specific) with the gamma-emitting radioactive isotope 57Co were compared. The radiolabelling efficiency of the MWCNT–MeAMN3S3sar conjugate was significantly higher (95% vs. 0.1%) (P ⩽ 0.001) than for the unconjugated pristine MWCNTs. This will allow for the potential tracking of nanoparticle movement in vitro and in vivo.

Layered double hydroxide (LDH) nanoparticles have the potential to benefit a myriad of medical, consumer and industrial products if intricate control of the nanoscale architecture and understanding of the biological interactions and potential toxicity of the LDH nanomaterials are achieved. Here, we report the synthesis and fractionation of LDH nanomaterials of well defined spatial characteristics through the careful control of synthesis conditions and the use of ultracentrifugation. The appropriateness of a range of fluorescent dyes, for labelling LDH nanoparticles to enable biological tracking, has also been investigated. These dyes include fluorescein, fluorescein isothiocyanate (FITC), 8-aminonaphthelene-1,3,6-trisulfonic acid (ANTS) and 8-aminopyrene-1,3,6-trisulfonic acid (APTS). Thermal degradation of the popular FITC dye during nanoparticle synthesis was revealed and suitable alternative fluorescent molecules established. Furthermore, we report for the first time the application of size exclusion chromatography on LDH nanoparticles as a fast, reliable and efficient method to achieve purification without causing nanoparticle agglomeration.

Layered double hydroxide (LDH) nanomaterials are currently the focus of intense scientific interest due to their potential application in drug and gene delivery research. However, the emerging field of nanotoxicology requires the development of new and more sensitive methodologies to follow the in vivo delivery kinetics as well as the persistence and bioaccumulation of the LDH carriers subsequent to delivery of the payload to the target area. Radioisotopic labeling offers very high detection sensitivity (

Stable and non-invasive fluorescent probes for nanotoxicological investigations are greatly needed to track the fate of nanoparticles in biological systems. The potential for terbium (Tb) to act as a fluorescent probe and its effect on layered double hydroxide (LDH) nanoparticle morphology are presented in this study. Incorporation of Tb during synthesis offers a simple methodology to easily tailor LDH nanoparticle thickness. A three-fold reduction in the average crystallite thickness (from 13 to 4 nm) has been achieved, whilst preferential lateral growth of LDH nanoparticles in the a-b crystal plane has been observed with increasing Tb loadings. Remarkably, Tb–LDH nanoparticles have emitted green fluorescence with a fluorescence quantum yield of 0.044.

Thin and short multi walled carbon nanotubes (MWNTs) were used to prepare nanocomposites based on poly(3-hexylthiophene) (P3HT). The MWNTs were characterized by TEG, SEM, TEM and Raman spectroscopy following deposition of films from stable dispersions of MWNT in chloroform. Non-covalent interaction between MWNT and P3HT dissolved in chloroform allowed the preparation of solution-cast composite films. Composite thermal events such as glass transition, melting temperature and heat of fusion were investigated by DSC and compared with pure polymer. Conductivity of composite bulk films was measured as a function of temperature by 2-point probe DC-resistance measurements. Loadings of MWNTs above 0.1 weight percent (wt%) in the conjugated polymer significantly increased the conductivity of P3HT composites. Interplay between charge transport through the semiconductor polymer and carbon nanotube network allowed the increase of conductivity after percolation to values close to 10-2 S cm-1, an improvement of four orders of magnitude over that of films cast from pure P3HT.

Hydrotalcites of formula Mg6A12(OH)16(PO4)·4H2O formed by intercalation with the phosphate anion as a function of pH show variation in the d-spacing attributed to the size of the hydrated anion in the interlayer. The value changes from 11.91 A for pH 9.3, to 7.88 A at pH 12.5. No crystalline hydrotalcites with phosphate in the interlayer were formed at pH 9.3. Thermal decomposition identifies three steps namely dehydration, dehydroxylation and some loss of carbonate during the thermal treatment. The addition of a thermally activated ZnAl-HT to a phosphate solution resulted in the uptake of the phosphate and the reformation of the hydrotalcite. The technology has the potential for water purification through anion removal.

A comprehensive spectroscopic analysis consisting of Raman, infrared (IR) and near infrared (NIR) spectroscopy was undertaken on the newly discovered mineral hoganite (copper(II) acetate monohydrate (Cu(CH(3)COO)(2) x H(2)O)). Assignments of vibrational bands due to the acetate anion have been made in all three forms of spectroscopy. Thermal analysis of the mineral was undertaken to follow its decomposition under a nitrogen atmosphere. Two major mass loss steps at 90 and approximately 220 degrees C were revealed. These mass losses correspond very well to firstly, the loss of a single water molecule, and then the loss of the acetate anion which quickly decomposes to form carbon dioxide and water.

This work reports a structure–property investigation of a conjugated polymer nanocomposite with enhanced conductivity. Regioregular poly(3-hexylthiophene) (rrP3HT) was used to prepare composites with thin, short, multi-walled carbon nanotube (MWNT) addition over a wide range of concentrations. Scanning and transmission electron microscopies demonstrated an excellent dispersion and good wetting properties within the carbon nanotube composites. Coated MWNTs showed superstructures of P3HT self-organized on nanotube surfaces. Changes in the long range order and on the self-ordered mesophase of the bulk material were investigated by infrared and Raman spectroscopies, differential scanning calorimetry and X-ray diffraction. Interplay between charge transport through the semiconducting polymer and carbon nanotube network increased the composite's conductivity after percolation to values close to 10 −2 S cm −1 .

Thermoanalytical and electron microscopic methods were used as characterisation tools for the determination of the composition of single walled carbon nanotube samples. Acid purification method of single-walled carbon nanotubes (SWCN) proved to be effective, resulting in a three fold increase in the percentage of SWNTs present in the purified product as determined by thermogravimetric analysis. In this work we report the thermogravimetric analysis by conventional and high resolution methods of the raw SWNTs and purified SWNTs.

Thermally activated hydrotalcite based upon a Zn/Al hydrotalcite with carbonate in the interlayer has been used to remove nitrate anions from an aqueous solution resulting in the reformation of a hydrotalcite with a mixture of nitrate and carbonate in the interlayer. X-ray diffraction of the reformed hydrotalcites with a d(003) spacing of 7.60 A shows that the nitrate anion is removed within a 30 min period. Raman spectroscopy shows that two types of nitrate anions exist in the reformed hydrotalcite (a) nitrate bonded to the 'brucite-like' hydrotalcite surface and (b) aquated nitrate anion in the interlayer. Kinetically the nitrate is replaced by the carbonate anion over a 21 h period. Two types of carbonate anions are observed. This research shows that the reformation of a thermally activated hydrotalcite can be used to remove anions such as nitrate from aqueous systems.

The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. The thermal decomposition of hydrotalcites with hexacyanoferrate(II) and hexacyanoferrate(III) in the interlayer has been studied using controlled rate thermal analysis technology. X-ray diffraction shows the hydrotalcites have a d(003) spacing of 10.9 and 11.1 A which compares with a d-spacing of 7.9 and 7.98 A for the hydrotalcite with carbonate or sulphate in the interlayer. Calculations show dehydration with a total loss of 7 moles of water proving the formula of hexacyanoferrate(II) intercalated hydrotalcite is Mg6Al2(OH)16[Fe(CN)6]0.5·7H2O and 9.0 moles for the hexacyanoferrate(III) intercalated hydrotalcite with the formula of Mg6Al2(OH)16[Fe(CN)6]0.66·9H2O. CRTA technology indicates the partial collapse of the dehydrated mineral. Dehydroxylation combined with CN unit loss occurs in two isothermal stages at 377 and 390°C for the hexacyanoferrate(III) and in a single isothermal process at 374°C for the hexacyanoferrate(III) hydrotalcite.

The thermal stability and thermal decomposition pathways for synthetic woodallite have been determined using thermogravimetry in conjunction with evolved gas mass spectrometry. Chemical analysis showed the formula of the synthesised woodallite to be Mg6.28Cr1.72Cl(OH)16(CO3)0.36⋅8.3H2O and X-ray diffraction confirms the layered LDH structure. Dehydration of the woodallite occurred at 65°C. Dehydroxylation occurred at 302 and 338°C. Both steps were associated with the loss of carbonate. Hydrogen chloride gas was evolved over a wide temperature range centred on 507°C. The products of the thermal decomposition were MgO and a spinel MgCr2O4. Experimentally it was found to be difficult to eliminate CO2 from inclusion in the interlayer during the synthesis of the woodallite compound and in this way the synthesised woodallite resembled the natural mineral.

The thermal stability and thermal decomposition pathways for synthetic iowaite have been determined using thermogravimetry in conjunction with evolved gas mass spectrometry. Chemical analysis showed the formula of the synthesised iowaite to be Mg6.27Fe1.73(Cl)1.07(OH)16(CO3)0.336.1H2O and X-ray diffraction confirms the layered structure. Dehydration of the iowaite occurred at 35 and 79°C. Dehydroxylation occurred at 254 and 291°C. Both steps were associated with the loss of CO2. Hydrogen chloride gas was evolved in two steps at 368 and 434°C. The products of the thermal decomposition were MgO and a spinel MgFe2O4. Experimentally it was found to be difficult to eliminate CO2 from inclusion in the interlayer during the synthesis of the iowaite compound and in this way the synthesised iowaite resembled the natural mineral.

Hydrotalcites with phosphate in the interlayer were prepared at different pH values. At pH >11.0 (PO4)(3-) was the intercalated ionic species, whereas at pH < 11.0 a mixture of (PO4)(3-) and (HPO4)(2-) ions was intercalated. Powder X-ray diffraction shows that the hydrotalcite formed at pH 9.5 is poorly diffracting with a d-spacing of 11.9 angstrom; whereas the d(003) spacing for the phosphate interlayered hydrotalcite formed at pH 11.9 and 12.5 was 8.0 and 7.9 angstrom respectively. The addition of a thermally activated ZnAl-HT to a phosphate solution resulted in the uptake of the phosphate and the reformation of the hydrotalcite. Raman spectroscopy of the phosphate interlayered hydrotalcites shows that the interlayered anion is pH dependent and only above pH 11.9 is the orthophosphate anion intercalated. At lower pH, the monohydrogen phosphate anion is intercalated. Raman spectroscopy shows that upon addition of the thermally activated hydrotalcite to an aqueous phosphate solution, results in the uptake of phosphate anion from the solution. Copyright (C) 2006 John Wiley & Sons, Ltd.

Plumbojarosite and argentoplumbojarosite were sources of lead and silver in ancient and medieval times. The understanding of the chemistry of the thermal decomposition of these minerals is of vital importance in ‘archeochemistry’. The thermal decomposition of plumbojarosite was studied using a combination of thermogravimetric analysis coupled to a mass spectrometer. Three mass loss steps are observed at 376, 420 and 502 ◦ C. These are attributed to dehydroxylation, loss of sulphate occurs at 599 ◦ C, and loss of oxygen and formation of lead occurs at 844 and 953 ◦ C. The temperatures of the thermal decomposition of the natural jarosite were found to be less than that for the synthetic jarosite. This is attributed to a depression of freezing point effect induced by impurities in the natural jarosite. Raman spectroscopy was used to study the structure of plumbojarosite. Plumbojarosites are characterised by stretching bands at 1176, 1108, 1019 and 1003 cm −1 and bending modes at 623 and 582 cm −1 . Changes in the molecular structure during thermal decomposition were followed by infrared emission spectroscopy.

Raman spectroscopy using a hot stage indicates that the intercalation of hexacyanoferrate(II) and (III) in the interlayer space of a Mg Al hydrotalcites leads to layered solids where the intercalated species is both hexacyanoferrate(II) and (III). Raman spectroscopy shows that depending on the oxidation state of the initial hexacyanoferrate partial oxidation and reduction takes place upon intercalation. For the hexacyanoferrate(III) some partial reduction occurs during synthesis. The symmetry of the hexacyanoferrate decreases from O-h, existing for the free anions to D-3d in the hexacyanoferrate interlayered hydrotalcite complexes. Hot stage Raman spectroscopy reveals the oxidation of the hexacyanoferrate(H) to hexacyanoferrate(III) in the hydrotalcite interlayer with the removal of the cyanide anions above 250 degrees C. Thermal treatment causes the loss of CN ions through the observation of a band at 2080 cm(-1). The hexacyanoferrate (III) interlayered Mg, At hydrotalcites decomposes above 150 degrees C. (c) 2005 Elsevier Inc. All rights reserved.

The thermal decomposition of hydrotalcites with chromate, molybdate and sulphate in the interlayer has been studied using thermogravimetric analysis coupled to a mass spectrometer measuring the gas evolution. X-ray diffraction shows the hydrotalcites have a d(0 0 3) spacing of 7.98 angstrom with very small differences in the d-spacing between the three hydrotalcites. XRD was also used to determine the products of the thermal decomposition. For the sulphate-hydrotalcite decomposition the products were MgO and a spinet MgAl2O4, for the chromate interlayered hydrotalcite MgO, Cr2O3 and spinel. For the molybdate interlayered hydrotalcite the products were MgO, spinet and MgMoO4. EDX analyses enabled the formula of the hydrotalcites to be determined. Two processes are observed in the thermal decomposition namely dehydration and dehydroxylation and for the case of the sulphate interlayered hydrotalcite, a third process is the loss of sulphate. Both the dehydration and dehydroxylation take place in three steps each for each of the hydrotalcites. (c) 2005 Elsevier B.V. All rights reserved.

Raman microscopy has been used to characterize the interlayer anions in synthesized hydrotalcites of formula Mg6Al2(OH)(16)(XO4)(.)4H(2)O, where X is S, Mo or Cr. The Raman spectrum shows that both the chromate and molybdate anions are not polymerized in the hydrotalcite interlayer. This lack of polymerization is attributed to the effect of pH during synthesis. A model of bonding is proposed for the interlayer anions based upon the observation of two symmetric stretching modes and symmetry lowering of the chromate, molybdate and sulphate anions. Two types of anions are present, hydrated and hydroxyl surface-bonded. Copyright (c) 2005 John Wiley & Sons, Ltd.

To further our understanding of nanoparticle interactions with biological systems, it is important that highly sensitive, reliable and robust methods for labelling particles are established. We report here the application of a series of bi-functional cage ligands to radiolabel a range (i.e. shapes and sizes) of titanium dioxide (TiO2) particles. The cages were covalently attached to the surface of the particles via the use of a dopac derivative and then radiolabelled with a gamma emitting radioisotope. The final radiolabelled nanoparticles proved to be stable in solution and the method easy and robust. The application of a gamma emitter allows the radiolabelled particles to be tracked in vivo and in the environment.

Carbon nanotubes (CNT) / conjugated polymer composites have been used for the preparation of thin film-modified electrodes. Thin, short, multi-walled CNT (MWNT) (purity higher than 95%) was completely coated by regioregular poly(3-hexylthiophene) (P3HT) through precipitation of a mixture of both in the non-solvent methanol. This work reports the electrochemical and optical characterization of P3HT and composites after dissolution in xylene and spin casting of films with thickness

Raman spectroscopy has been utilized to show the increase of single-walled carbon nanotubes (SWCNTs) content in commercial grade samples synthesized by the chemical vapour deposition (CVD) technique with a minimization of impurities using both hydrochloric acid treatment and surfactant purification. Surfactant purification methods proved to be the most effective, resulting in a three-fold increase in the percentage of SWCNTs present in the purified product as determined by Raman spectroscopy.

Molecular-resolved real-space images of self-assembled structures of the conductive polymer regioregular poly(3- hexylthiophene) (rrP3HT) on single-walled carbon nanotubes (SWNT) were obtained using scanning tunneling microscopy (STM). The STM images revealed that the adsorbed polymer typically formed a 10 nm thick coating on SWNT's. This is in agreement with transmission electron microscopy (TEM) results for drop-cast composite films that provided strong evidence that SWNTs were isolated in a polymer matrix and coated with rrP3HT multilayers. A 10 nm thick deposit corresponds to a coating of ~25 layers of polymer on SWNT, assuming that π-π interactions between rrP3HT layers determine deposition and that the underlying SWNT directs the polymer self-assembly process. STM measurements of adsorbed monolayers and multilayers of rrP3HT on SWNT surfaces were compared to rrP3HT monolayer and multilayer deposition on highly ordered pyrolytic graphite (HOPG) surfaces. The average inter-lamellar distances of adsorbed polymer was greater for both rrP3HT monolayer and multilayer films adsorbed onto the curved surfaces of SWNTs than on the flat surfaces of HOPG samples. Analysis of STM images yielded the interchain spacings of adsorbed macromolecules, d cc = 1.55 - 1.68 ± 0.02 nm. The polymer was observed to wrap around some SWNTs at an angle with respect to the SWNT long-axis, which indicated that the rrP3HT self-assembly is hierarchical. The conductive polymer's deposition appears to occur with epitaxy and is directed by the underlying SWNT chiral structure.

A comprehensive spectroscopic analysis consisting of Raman, infrared (IR) and near-infrared (NIR) spectroscopy was undertaken on two forms of calcium acetate with differing degrees of hydration. Monohydrate (Ca(CH(3)COO)(2).H(2)O) and half-hydrate (Ca(CH(3)COO)(2).0.5H(2)O) species were analysed. Assignments of vibrational bands due to the acetate anion have been made in all three forms of spectroscopy. Thermal analysis of the mineral was undertaken to follow its decomposition under a nitrogen atmosphere. Three major mass loss steps at approximately 120, 400 and 600 degrees C were revealed. These mass losses correspond very well to firstly, the loss of co-ordinated water molecules, and then the loss of water from the acetate anion, followed by finally the loss of carbon dioxide from the carbonate mineral to form a stable calcium oxide.

Molecular-resolved real-space images of self-assembled structures of the conductive polymer regioregular poly(3-hexylthiophene) (rrP3HT) on single-walled carbon nanotube (SWNT) substrates were obtained using scanning tunneling microscopy (STM). The STM images revealed that the adsorbed polymer formed a 10 nm thick coating on some SWNT's in agreement with previous transmission electron microscopy results. This thickness corresponds to a coating of ~25 layers of polymer on SWNT, assuming that pi-pi interactions between rrP3HT layers and the underlying SWNT directs the polymer self-assembly process. The polymer backbone interchain spacing (dcc = 1.55 nm) of the outermost layer of adsorbed rrP3HT is approximately 7% larger than is observed for rrP3HT adsorbed on HOPG (dcc = 1.45 nm). The polymer also wraps around the SWNT at an angle with respect to the SWNT long-axis, which indicates that rrP3HT self-assembly is hierarchical. The conductive polymer's deposition occurs with epitaxy and is directed by the underlying SWNT chiral structure

Single walled carbon nanotubes (SWNTs) were incorporated in polymer nanocomposites based on poly(3-octylthiophene) (P3OT), thermoplastic polyurethane (TPU) or a blend of them. Thermogravimetry demonstrated the success of the purification procedure employed in the chemical treatment of SWNTs prior to composite preparation. Stable dispersions of SWNTs in chloroform were obtained by non-covalent interactions with the dissolved polymers. Composites exhibited glass transitions, melting temperatures and heat of fusion which changed in relation to pure polymers. This behavior is discussed as associated to interactions between nanotubes and polymers. The conductivity at room temperature of the blend (TPU-P3OT) with SWNT is higher than the P3OT/SWNT composite.

A detailed study of poly(alkylthiophene) self-assembly and organization on single-walled carbon nanotubes (SWNTs) is presented. Experimental evidence for self-assembly and organization of regioregular poly(3-hexyl thiophene) (rrP3HT) on single-walled carbon nanotubes was obtained using scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). TEM images of drop-cast rrP3HT/SWNT composites displayed strong evidence that SWNTs were isolated from each other in a polymer matrix and coated with between 1-3 layers rrP3HT. STM measurements of adsorbed monolayers of rrP3HT on SWNT surfaces were compared to rrP3HT monolayer deposition on highly ordered pyrolytic graphite (HOPG) surfaces. The results show that average inter-lamellar distances of adsorbed polymer are greater for rrP3HT monolayers adsorbed onto the curved surfaces of SWNTs than on the flat surfaces of HOPG samples. Analysis of STM images yielded the chiral angles at which the thiophene polymer chains wrap around individual carbon nanotubes (41-48o with respect to nanotube axis) while the interchain spacings of adsorbed macromolecules was 1.68 ± 0.02 nm. Comparisons between the native polymer deposited on graphite and the composite structure confirmed that the presence of carbon nanotubes in rrP3HT produces a material with a high degree of order at the molecular level. This high level of order and close coupling of the two components of the composite are prerequisites for its use as the active layer of an organic photovoltaic.

Raman scattering of molecules adsorbed on the surface of TiO(2) nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO(2) nanoparticles. An enhancement factor up to approximately 10(3) was observed in the solutions containing TiO(2) nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO(2) surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules that lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.

Characterisation of clays is generally achieved by traditional methods, such as X-ray diffraction (XRD) and transmission electron microscopy (TEM). However, clays are often difficult to characterise due to lack of long-range order, thus these tools are not always reliable. Because interlayer spacing in clays can be adjusted to house molecules, there is growing interest to use these materials for drug delivery. Positron annihilation lifetime spectroscopy (PALS) was examined as an alternative tool to characterise a series of well-known clays. XRD of two layered double hydroxides; MgAl-LDH and MgGd-LDH, natural hectorite, fluoromica and laponite, and their PALS spectra were compared. XRD data was used to calculate the interlayer d- spacing in these materials and results show a decrease in interlayer spacing as the heavy metal ions are substituted for those of large ionic radii. Similar results were obtained for PALS data. This preliminary study suggests PALS has potential as a routine tool for characterising clay particles. Further work will examine the sensitivity and reliability of PALS to percent of metal doping and hydration in clay microstructure.

Nanoparticles rapidly interact with the proteins present in biological fluids, such as blood. The proteins that are adsorbed onto the surface potentially dictate the biokinetics of the nanomaterials and their fate in vivo. Using nanoparticles with different sizes and surface characteristics, studies have reported the effects of physicochemical properties on the composition of adsorbed plasma proteins. However, to date, few studies have been conducted focusing on the nanoparticles that are commonly exposed to the general public, such as the metal oxides. Using previously established ultracentrifugation approaches, two-dimensional gel electrophoresis and mass spectrometry, the current study investigated the binding of human plasma proteins to commercially available titanium dioxide, silicon dioxide and zinc oxide nanoparticles. We found that, despite these particles having similar surface charges in buffer, they bound different plasma proteins. For TiO2, the shape of the nanoparticles was also an important determinant of protein binding. Agglomeration in water was observed for all of the nanoparticles and both TiO2 and ZnO further agglomerated in biological media. This led to an increase in the amount and number of different proteins bound to these nanoparticles. Proteins with important biological functions were identified, including immunoglobulins, lipoproteins, acute-phase proteins and proteins involved in complement pathways and coagulation. These results provide important insights into which human plasma proteins bind to particular metal oxide nanoparticles. Because protein absorption to nanoparticles may determine their interaction with cells and tissues in vivo, understanding how and why plasma proteins are adsorbed to these particles may be important for understanding their biological responses.