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Glaciers and ice sheets are a significant source of nanoparticulate Fe, which is potentially important in sustaining the high productivity observed in the near-coastal regions proximal to terrestrial ice cover. However, the bioavailability of particulate iron is poorly understood, despite its importance in the ocean Fe inventory. We combined high-resolution imaging and spectroscopy to investigate the abundance, morphology and valence state of particulate iron in glacial sediments. Our results document the widespread occurrence of amorphous and Fe(II)-rich and Fe(II)-bearing nanoparticles in Arctic glacial meltwaters and iceberg debris, compared to Fe(III)-rich dominated particulates in an aeolian dust sample. Fe(II) is thought to be highly biolabile in marine environments. Our work shows that glacially derived Fe is more labile than previously assumed, and consequently that glaciers and ice sheets are therefore able to export potentially bioavailable Fe(II)-containing nanoparticulate material to downstream ecosystems, including those in a marine setting. Our findings provide further evidence that Greenland Ice Sheet meltwaters may provide biolabile particulate Fe that may fuel the large summer phytoplankton bloom in the Labrador Sea, and that Fe(II)-rich particulates from a region of very high productivity downstream of a polar ice sheet may be glacial in origin.

Oleic acid capped CoFe 2 O 4 nanoparticles which exhibit a high coercivity of ∼9.47 kOe at room temperature were coated with a robust coating of SiO 2 . We have used chemical synthesis method to obtain SiO 2 coated CoFe 2 O 4 nanoparticles with different weight percentages of CoFe 2 O 4 in SiO 2 (1.5, 3.1 and 4.8 wt.%). The morphological investigation of the coated nanoparticles by transmission electron microscopy shows that the particles are spherical with average size ∼160 nm. Infrared spectroscopy reveals that oleic acid capping on the surface of CoFe 2 O 4 nanoparticles is retained after silica coating process. The complete coating of SiO 2 on CoFe 2 O 4 nanoparticles is confirmed by X-ray photoelectron spectroscopy as there is no signature of cobalt or iron ions on the surface. Magnetic measurements show that coercivity of SiO 2 coated CoFe 2 O 4 particles remains more or less unaffected as in CoFe 2 O 4 nanoparticles at room temperature. In addition, the temperature dependent magnetic measurements show that at 5 K the CoFe 2 O 4 and SiO 2 coated 1.5 wt.% CoFe 2 O 4 samples exhibit a very high value of coercivity (∼20 kOe) which is more than twice as compared to room temperature coercivity value (∼9.47 kOe). We conclude that silica coating in our study does not significantly affect the coercivity of CoFe 2 O 4 nanoparticles.

A recent assessment (Giovannelli, G., D'Urzo, L., Maggiulli, G., Natali, S., Pagliara, C., Sgura, I. & Bozzini, B. 2010. Journal of Solid State Electrochemistry, 14: 479–94.) of the corrosion state...

This paper reports on the electrodeposition of Mn–Cu–ZnO for hybrid supercapacitors. This material exhibits a dual structure consisting of Mn-rich highly active, but poorly electronically conducting, grains, which are locked by a Cu-rich highly conductive network that also possesses some degree of charge-storage capacity. This work focuses on morphological, compositional, and chemical-state distributions with submicrometer lateral resolution. This information, which is crucial because doping distribution controls supercapacitor performance, has been obtained by combining electrochemical and in situ Raman measurements with synchrotron-based X-ray fluorescence and absorption microspectroscopy. Using a microfabricated thin-layer three-electrode microcell, we followed the morphochemical changes at different electrodeposition stages and found that pulse-plating allows the growth of Mn- and Cu-doped ZnO as self-organized structures with a consistent spatially stable composition distribution.

Gold nanorods (GNRs) have been fabricated by a novel polymer-immobilised seed mediated method using ultraviolet (UV) photoreduced gold-polymethylmethacrylate (Au–PMMA) nanocomposites as a seed platform and characterised at sub-micron scale regime with synchrotron-based techniques; near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray fluorescence (XRF) mapping. In this report, it is shown that investigating polymer nanocomposites using combination of XRF mapping and NEXAFS spectromicroscopy can help to see the growth phenomenon from different perspective than conventional characterisation techniques. XRF maps are used to explore distribution of the constituent elements and showing how polymer matrix making stripe patterns along with regions where GNRs are formed. NEXAFS carbon (C) K-edge spectra have been taken at three different stages of synthesis: (1) on Au–PMMA nanocomposites before UV irradiation, (2) after gold nanoparticles formation, and (3) after GNRs formation. It reveals how polymer matrix has been degraded during GNRs formation and avoiding chemically or physically damage to polymer matrix is crucial to control the formation of GNRs.

In view of improved durability, the study of electrocatalyst supports for PEMFCs alternative to carbon is raising notable research interest. In this paper we investigated the oxidation of ethanol on WC-supported electrodeposited Pt, in pristine and aged conditions by: (i) electrochemical measurements, (ii) in situ spectroscopy (FTIR and sum-frequency generation spectroscopy (SFG)) carried out during the electro-oxidation of ethanol and (iii) ex situ synchrotron-based space-resolved photoelectron spectroscopy (SPEM). The complementarity of FTIR and SFG allows an insightful understanding of the electrochemical interface as a function of applied potential and catalyst ageing. In situ FTIR and SFG revealed adsorbed acetate and ethanol, in addition to linearly and bridge-bonded CO and solution-phase CO2. The Stark tuning of CO indicates that it is less strongly bonded to aged electrodes. Quantitative analysis of potential-dependent FTIR and SFG spectra reveals that the population of adsorption sites for CO, acetate and ethanol changes with ageing and correlates with loss of catalytic activity. Changes in catalyst morphology as well as Pt and WC chemical state have been pinpointed by SPEM: electrodeposited Pt nanoparticles tend to agglomerate and the distribution of oxidised and reduced forms of Pt and W correlates with the attack of the catalyst support.

This paper reports the first in-situ synchrotron-based scanning photoelectron microscopy study of an operating YSZ-supported single-chamber SOFC with Au–MnO2 composite cathode and NiO anode, fed with 10−5 mbar 1:1 mixture of CH4 fuel and O2 at 650 °C. We employed a YSZ-supported cell with Au–MnO2 composite cathode and NiO anode. The chemical imaging and micro-XPS results were complemented with simultaneous electrochemical measurements, open circuit potential, potentiostatic and impedance spectrometry. The cell was operated under two conditions: (i) with fully oxidized electrodes and (ii) after in-situ reductive activation of the anode. The current delivered by the cell after in-situ reduction was about one order of magnitude higher. The chemical states of Ni and Mn were affected by the in-situ reduction process but they were not modified by the fuel-cell operation. Notwithstanding the absence of chemical state transformations of the electrode materials during the prolonged fuel-cell operation, cell aging brings about morphological change, accompanied by a decrease of the extracted current. Keywords: SOFC, Single-chamber SOFC, Hydrocarbon-fuelled SOFC, SPEM, XPS, X-ray microscopy

The existence and role of platinum oxide in the solid state electrode system Pt(O2)/yttria-stabilized zirconia is discussed. Covering and porous model-type Pt film electrodes on YSZ single crystals are investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and in situ scanning photoelectron microscopy. The formation of Pt oxide and its amount strongly depend on the experimental conditions, such as temperature, oxygen partial pressure, and oxygen flux towards the electrode during anodic polarization. Electrode activation and deactivation processes can be explained by formation and decomposition of Pt oxide, which is reducing or inhibiting the oxygen exchange rate.

The performance of new materials and devices often depends on processes taking place at the interface between an active solid element and the environment (such as air, water or other fluids). Understanding and controlling such interfacial processes require surface-specific spectroscopic information acquired under real-world operating conditions, which can be challenging because standard approaches such as X-ray photoelectron spectroscopy generally require high-vacuum conditions. The state-of-the-art approach to this problem relies on unique and expensive apparatus including electron analysers coupled with sophisticated differentially pumped lenses. Here, we develop a simple environmental cell with graphene oxide windows that are transparent to low-energy electrons (down to 400 eV), and demonstrate the feasibility of X-ray photoelectron spectroscopy measurements on model samples such as gold nanoparticles and aqueous salt solution placed on the back side of a window. These proof-of-principle results show the potential of using graphene oxide, graphene and other emerging ultrathin membrane windows for the fabrication of low-cost, single-use environmental cells compatible with commercial X-ray and Auger microprobes as well as scanning or transmission electron microscopes.

This paper reports on the electrochemical reduction of bichromate from an aqueous solution at a Pt(1 1 1) electrode studied by voltammetry and synchrotron-based photoelectron spectromicroscopy Cathodic reduction is carried out at potentials −1.5 and −2.0 eV in an electrochemical cell attached to the UHV chamber hosting the scanning photoelectron microscope (SPEM), which allowed sample transfer for SPEM analysis without exposure to the air. The Cr 2p and Pt 4f core level spectra are used as fingerprints of the Cr lateral distribution and chemical state after reduction. The Pt 4f and Cr 2p maps show inhomogeneous Cr distribution in microscopic Cr-rich and Cr-poor islands. Analysis of the Pt 4f, Cr 2p photoemission peaks recorded in these islands has disclosed that – under both reduction conditions – Cr(VI) is reduced principally to Cr(III), with ca. 10% of Cr(0) localised in the Cr-rich islands. The presence of an intermediate oxidation state has also been detected, that can be assigned to a transition state from Cr(VI) to Cr(III).

In this paper we report an investigation of the degradation of the Pt/C electrocatalyst of an anodic membrane-electrode assembly (MEA) after 1000 h of operation in a laboratory single-cell PEMFC, using synchrotron-based space-resolved photoelectron spectroscopy. This study is complemented by the analysis of a pristine MEA and reference materials, as well as by electrochemical measurements, SEM imaging and energy-dispersive X-ray fluorescence spectroscopy (EDX). Catalyst ageing correlates with a corrugation of morphology, as observed by SEM and scanning photoelectron microscopy (SPEM), corresponding to Pt nanoparticle agglomeration. Moreover – on the basis of high lateral resolution SPEM, X-ray photoelectron spectroscopy (XPS) and EDX analyses, – we found that, after operation, Pt is transported onto the fibres of the gas-diffusion layer (GDL). Space-resolved XPS shows a peak shift of the Pt 4f 7/2 level to higher and lower binding energies with respect to Pt(1 1 1) and pristine Pt black, respectively, corresponding to nanocrystallinity in the first case and agglomeration in the second one. No oxidised Pt was found in any location of the anodically used MEA.

The paper reports the results of an extensive characterization of the Ti6Al4V-SiCfcomposite produced by hot isostatic pressing (HIP) to assess its capability to withstand the in-service conditions of turbine blades operating at middle temperatures in aeronautical engines. The microstructure of composite, in as-fabricated condition and after long-term heat treatments (up to 1,000 hours) in the temperature range 673-873 K, has been investigated by means of different techniques. Particular attention was paid to the micro-chemical evolution of fibre-matrix interface which is scarcely affected also by the most severe heat treatments examined here. This leads to stable mechanical properties as evidenced by hardness, tensile and FIMEC instrumented indentation tests. Therefore, the composite can operate at the maximum temperature (873 K) foreseen for its aeronautical applications without remarkable modifications of its microstructure and degradation of mechanical properties. The mechanical characterization has been completed by internal friction and dynamic modulus measurements carried out both at constant and increasing temperature, from 80 to 1173 K.

Scanning photoelectron microscopy (SPEM) is a powerful technique to image and probe micro and nano-structures. Recent achievements on imaging the sub-micro objects will be present in this report. For the first time, SPEM is used to explore and probe the chemical state and chemical composition of individual ZnO nanostructures. The capability of SPEM on imaging an individual MWCNT is shown which is down to 50 nm in diameter. The MWCNTs, partially covered with a metal, successfully are fabricated and presence of a sharp interface between CNT and metal is confirmed by SPEM. The morphology, composition and oxidation/reduction of isolated supported PtRh micro- and nano- particles produced by pulsed-laser deposition (PLD) have been investigated by SPEM. [DOI: 10.1380/ejssnt.2011.158]

Prickly nanostructures of ZnO have been obtained by the hydrothermal synthesis technique. Structures are analyzed using X-ray diffraction, electron microscopy as well as photoelectron spectromicroscopy. The analysis revealed that the prickly ZnO nanostructures are highly crystalline with hexagonal wurtzite phase and possess homogeneous compositional structures. They are assembled of nanothread structures with narrow thickness distribution around 30 nm. The valence band analysis revealed that there are peaks due to the bonding, nonbonding, and antibonding of the zinc and oxygen orbitals. These nanostructures exhibit intense near band-edge emission. Photoluminescence analysis showed that the structures also give defect-induced blue emission along with green emission.

Gold–polymethylmethacrylate (PMMA) nanocomposites were fabricated with a photoreduction method using UV irradiation. The irradiated samples are compared with unirradiated ones to investigate the mechanism of gold nanoparticle formation and the effect of UV irradiation and polymer matrix on the morphology of the particles. The triangular gold nanoparticles were formed in polymer medium at a specific concentration of gold salt and UV exposure. The particle size decreased when the gold salt to polymer ratio was increased. The samples were analysed using UV–Vis spectroscopy, Fourier transform infrared spectrometry, atomic force microscopy, x-ray diffraction, small angle x-ray scattering and x-ray photoelectron spectroscopy. The interfacial interaction of Au nanoparticles and PMMA polymer has been discussed.

Synthesis of silver nanoparticles using alpha-NADPH-dependent nitrate reductase and phytochelatin in vitro has been demonstrated for the first time. The silver ions were reduced in the presence of nitrate reductase, leading to the formation of a stable silver hydrosol 10-25 nm diam. and stabilized by the capping peptide. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-Vis absorption. These studies will help in designing a rational enzymatic strategy for the synthesis of nanomaterials of different chemical composition, shapes and sizes as well as their separation.

Fuel cells are one of the most appealing environmentally friendly devices for the effective conversion of chemical energy into electricity and heat, but still there are key barriers to their broad commercialization. In addition to efficiency, a major challenge of fuel-cell technology is the durability of the key components (interconnects, electrodes, and electrolytes) that can be subject to corrosion or undesired morphology and chemical changes occurring under operating conditions. The complementary capabilities of synchrotron-based soft X-ray microscopes in terms of imaging, spectroscopy, spatial and time resolution, and variable probing depths are opening unique opportunities to shed light on the multiple processes occurring in these complex systems at microscopic length scales. This type of information is prerequisite for understanding and controlling the performance and durability of such devices. This paper reviews the most recent efforts in the implementation of these methods for exploring the evolving structure and chemical composition of some key fuel cell components. Recent achievements are illustrated by selected results obtained with simplified versions of proton-exchange fuel-cells (PEFC) and solid-oxide fuel-cells (SOFC), which allow in situ monitoring of the redox reactions resulting in: 1) undesired deposits at interconnects and electrodes (PEFC); 2) material interactions at the electrode-electrolyte interface (PEFC); 3) release of corrosion products to the electrolyte phase (PEFC, and 4) mass-transport processes and structural changes occurring at the high operation temperatures of SOFC and promoted by the polarization.

Cobalt/polypyrrole ORR electrocatalysts has been electrochemically synthesized by a potentiostatic anodic/cathodic pulse-plating procedure. The deposition electrochemistry has been studied by cyclic voltammetry and in-situ Micro Raman Spectroscopy complemented with scanning X-ray microscopy and micro-spot X-ray absorption spectroscopy (mu-XAS). Linear sweep voltammetry (LSV) under oxygen reduction has been used to assess the electrocatalytic effect of as-electrodeposited Co/PPy. The obtained results have provided new information about the concomitant electropolymerisation and metal incorporation processes occurring under different pulsed co-electrodeposition conditions, important for optimising the electrosynthesis procedure. The colocation of O and Co, evidenced by the O and Co XRF maps indicates that the Co in the formed composite is in oxidized state and for composites formed at low currents using shorter Co pulses coexistence of both CoO and Co3O4 is evidenced by the Co L-3 XAS spectra. Bimodal Co distribution as micro-grains on a background of nano-grains and co-nulcleation of PPy and Co is evidenced by correlation of Co and N XRF maps.

Synthesis of thioglycerol capped zinc selenide nanoparticles with a relatively narrow size distribution by a simple and inexpensive low temperature (~ 80 °C) wet chemical method is reported here. Main advantage of this method is the use of non-toxic precursors. The size of the nanoparticles can be varied easily by changing the concentration of the capping agent. The extracted nanoparticles remain stable under normal atmospheric conditions and can be redispersed in suitable solvents. The sharp absorption features obtained in the UV–Visible absorption spectra reveal the formation of monodispersed ZnSe nanoparticles. The nanoparticles were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, UV–Visible absorption spectroscopy, photoluminescence and transmission electron microscopy.

The control of the doping in nanowires (NWs) is of fundamental importance for the implementation of NW-based devices. A method is presented to obtain local information about doping by monitoring the Fermi-energy position within the bandgap at the surface along single NWs through spatially resolved x-ray photoemission spectroscopy. The experimental results are complemented by theoretical simulations of the carrier profile, taking into account the presence of electronic surface states and quantifying the impact of carrier depletion at the NW surface. This combined approach allows to determine the effect of the incorporation of Si dopants in GaAs NWs following different growth protocols, such as vapor-liquid-solid axial growth or vapor-solid radial growth, and in the resulting core-shell structures and axial junctions. The method also revelaed the strong dependence of the resulting doping on the morphology of the single NW (orientation, shell thickness). This approach can be easily applied to other nanoscale objects, allowing the direct observation of how doping (or junctions, or adsorbates,.) may locally affect the position of the Fermi level at the surface, which is a crucial factor in several application fields, such as photovoltaic and photocatalysis. (C) 2013 AIP Publishing LLC.

The piezoresistive response of copper and nickel particles reinforced polydimethylsiloxane (PDMS) polymer, forming metal-polymer composites were investigated under uniaxial pressure. Electrical and mechanical properties of composite samples containing Cu and Ni conductive fillers at different loadings in polydimethylsiloxane (PDMS) polymer matrix have been presented here. Well-dispersed metal-polymer composites were fabricated by a wet mixing route. The resulting Cu-PDMS and Ni-PDMS composite samples show the resistivity changes by more than 2 and 10 orders of magnitude around 4MPa pressure, respectively. The mechanical tests have shown that these composite samples have high stress sensitivity which makes them good piezoresistive candidates for practical applications.

Replacement of hydrogen with hydrocarbon fuels in solid-oxide fuel cells (SOFCs) is an appealing alternative for reducing the implementation costs of SOFCs technology, but the electrode stability and susceptibility to carbon deposition still remain important issues to be solved. The present in situ photoelectron microscopy study of a prototype hydrocarbon-fuelled SOFC, operated at 650 °C in C2H4 + H2O gas mixture and voltages in the range 0−3 V, provides insights into morphologychemistry changes of the Ni electrodes and Cr interconnects with decisive impact on the electrochemical activity and durability. The results reveal the combination of thermal and electromigration of Ni across the electrode−electrolyte interface that can cause sensible material losses and structural changes responsible for the deterioration of device performance. The C 1s spectra evidence deposition of C and formation of carbides on the Ni electrodes and Cr interconnects at 650 °C as result of C2H4 dissociation, the process being promoted applying cathodic potential and reversed by switching to anodic potential. Following the attenuation of the C signal under anodic potential, the effect of the stability of different carbides on the reaction rate was observed.

Gold?polymethylmethacrylate (PMMA) nanocomposites were fabricated by mixing gold nanoparticles capped with oleylamine in polymethylmethacrylate. The samples were analysed using UV?vis absorption spectroscopy, transmission electron microscopy, small angle x-ray scattering, Fourier transform infrared spectrometry (FTIR) and x-ray photoelectron spectroscopy (XPS). Electrical resistivity of nanocomposite samples was measured by a four-probe technique in the 70?300?K range. The nanocomposites showed a transition with an onset at ~160?165?K. They exhibited a semiconductor-like conductivity at higher temperatures and nearly temperature independent conductivity at lower temperatures. The interfacial interaction of Au nanoparticles and PMMA polymer is investigated using FTIR and XPS. A ligand-exchange process occurs when capped gold nanoparticles are incorporated in PMMA polymer.

Scanning photoemission spectromicroscopy is a powerful tool for the chemical characterization of materials based on third generation synchrotron light sources. Due to the X-ray fo calization properties it represents also an extremely bright source of radiation ideal for the investigation of radiation e ffects on matter. Despite the experiments involving inorganic materials, such as oxides, lead in the last decade have alr eady shed light on the potentials of this techniques to perform lateral resolved chemical analysis, still there is a lack of information concerning the possibilities to measure organic compounds. This paper reports on the investigation of inorganic (Rh oxide thin films) and organic (polymers) samples performed with the scanning photoemission microscope hosted at the Elettra Synchrotron Light Laboratory. Results show that the typical photon densities in the focused spot of the microscope allow the investigation of the oxide films but produce an immediate damaging of the polymeric film. Keywords: X-ray damage, X-ray photoemission spectromicroscopy, polymers.

The present in situ study of electrochemically induced processes occurring in Cr/Ni bilayers in contact with a YSZ electrolyte aims at a molecular-level understanding of the fundamental aspects related to the durability of metallic interconnects in solid oxide fuel cells (SOFCs). The results demonstrate the potential of scanning photoelectron microspectroscopy and imaging to follow in situ the evolution of the chemical states and lateral distributions of the constituent elements (Ni, Cr, Zr, and Y) as a function of applied cathodic potential in a cell working at 650 degrees C in 10(-6) mbar O(2) ambient conditions. The most interesting findings are the temperature-induced and potential-dependent diffusion of Ni and Cr, and the oxidation-reduction processes resulting in specific morphology-composition changes in the Ni, Cr, and YSZ areas.

Nanocrystalline titanium oxide (TiO 2 ) is one of the most useful oxide material, because of its widespread applications in photocatalysis, solar energy conversion, sensors and optoelectronics. The control of particle size and monodispersity of TiO 2 nanoparticles is a challenging task. The use of MCM-41, an inorganic template of uniform pore size (2-10 nm), can overcome this difficulty and produce stable nanoparticles of uniform size and shape. Here, we demonstrate the synthesis of titania nanoparticles inside the pores of silica based MCM-41 forming a TiO 2 /Si-MCM composite. Composites are formed in the alcoholic medium by incipient wetness impregnation method. Titania particles of average 3 nm size are obtained. Effect of silica and titania precursors on the quality of nanoparticles has been investigated. The characterization of titania-MCM-41 composites has been carried out using a variety of techniques like UV-vis absorption spectroscopy, X-ray diffraction, FT-IR spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. It has been found that the titania particles are co-ordinated with Si-MCM by Si-O-Ti covalent bond.

Rapid switching (5–15 minutes) in the wettability of titania (TiO2) thin films in the anatase phase has been observed after UV irradiation. The film surface becomes superhydrophilic when exposed to UV radiation. The relationship between wettability, thickness and crystallinity of TiO2 films has been investigated. Amorphous and anatase TiO2 thin films have been deposited by varying the argon to oxygen gas ratio, using the reactive dc magnetron sputtering technique. It was found that the gas ratio primarily affects thickness, crystallinity, morphology and wettability of the films. The highest contact angle that has been reported so far, namely, 170°–176°, has been observed for film thickness varying from 112–500 nm in the case of pristine anatase TiO2 films. On the other hand, amorphous films show a variation in the contact angle from 120° to 140° as the thickness varied from 70 to 145 nm. The deposition is extremely robust and has an ultralow hysteresis in the contact angle. The films exhibit a morphology similar to the lotus leaf and the water hyacinth.

Investigations on the piezoresistive response of composites containing zinc conductive fillers at different concentrations in polydimethylsiloxane (PDMS) polymer matrix are presented here. The composites remain insulating even at high filler concentrations. The piezoresistive behaviour of the Zn–PDMS composites under uniaxial pressure shows the resistivity changes by approximately seven orders of magnitude around 4 MPa pressure. We find that the piezoresistive behaviour of the Zn–PDMS composites can be explained in the framework of electron tunnelling between the metal particles.

An enzymatic synthesis route to peptide-capped gold nanoparticles has been developed. Gold nanoparticles were synthesized using alpha-NADPH-dependent sulfite reductase and phytochelatin in vitro. The gold ions were reduced in the presence of the enzyme sulfite reductase, leading to the formation of a stable gold hydrosol of dimensions 7-20 nm and were stabilized by the capping peptide. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-visible optical absorption. These studies will help in designing a rational enzymatic strategy for the synthesis of nanomaterials of different chemical compositions, shapes and sizes as well as their separation.