Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

The design and synthesis of high-efficiency materials to convert solar to electrical energy is an increasingly important research field. Within the photovoltaic technologies, crystalline Si have an 80% share while the remaining 20% are mostly thin film solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe) and CdTe. However, the cost, the abundance and the environmental impact of the elemental components cannot be neglected. For these reasons, Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe) and their solid solutions CZTSSe has attracted much attention recently since they can provide the development of cost competitive solar cells. The CZTS-based solar cells consist of earth abundant and relatively inexpensive elements and represent an environmentally friendly alternative compared to the above mentioned systems. The energy conversion efficiency of the CZTS-based solar cells has increased from 0.66% in 1996 to 11.1% recently.

The present work shows preliminary results that are related to the characterization of CZTSSe monograin powders by scanning electron microscopy. High purity metal compounds, S and Se powders were used as precursors for the synthesis of the Cu2ZnSn(SSe)4 monograin powders. The precursor powders were mixed to the desired composition and, additionally, KI was added as a flux material. Afterwards, the powders were blended in a mixer and encapsulated in quartz ampoules. The blended powders were degassed under dynamic vacuum at room temperature, sealed and annealed isothermally between 700 ºC and 780 ºC for a time ranging between 44 h and 136 h. After synthesis the flux material was removed with deionized water and the powders were sieved into several fractions. The morphology, microstructure and chemical composition of the synthesized powders was obtained with a Philips XL30 field-emission scanning electron microscope (FE-SEM) equipped with a backscattered electron (BSE) detector and an integrated EDAX energy dispersive X-ray spectroscopy (EDS) microanalysis system.

The typical morphology obtained for the CZTSSe powders can be seen in Figure 1. Basically, the particles show a polyhedral morphology with some of them showing a needle shape, i.e. a large shape factor (L/D>>1). Moreover, it was also observed a slight increase of the median particle size with the increase of the synthesis temperature. Due to the complexity of the synthesis of CZTSSe monograins, the formation of binary or ternary phases is a common feature. A very good control over the synthesis parameters is then required not only to obtain the desired phase but also to have a tight control over the stoichiometry of the material. Taking this into account, SEM/BSE observations and EDS analysis are two powerful techniques for evaluate the degree of the compositional homogeneity of the CZTSSe monograins. Figure 2 puts in evidence the degree of the homogeneity of the CZTSSe monograins in relation to their size. Overall, and independently of the synthesis conditions, the powder particles consisted predominantly of CZTSSe monograins and, in a much smaller extent, of particles having a ZnS or ZnS(Se) core coated by a CZTSSe layer. The presence of undesired phases occurred more frequently in the larger powder particles (> 100 µm) and the degree of homogeneity was lower for the powders synthesized at lower temperature and for a shorter time. However, when the EDS results obtained for CZTSSe monograins belonging to different size fractions are compared no major variations in the content of the five elements can be inferred.

Zinc Oxide is a wide band-gap compound semiconductor that has been used in optoelectronic and photovoltaic applications due to its good electrical and optical properties. Aluminium has been an efficient n-type dopant for ZnO to produce low resistivity films and high transparency to visible light. In addition, the improvement of these properties also depends on the morphology, crystalline structure and deposition parameters. In this work, ZnO:Al films were produced by d.c. pulsed magnetron sputtering deposition from a ZnO ceramic target (2.0 wt% Al2O3) on glass substrates, at a temperature of 250 ºC.

The crystallographic orientation of aluminum doped zinc oxide (ZnO:Al) thin films has been studied by Electron Backscatter Diffraction (EBSD) technique. EBSD coupled with Scanning Electron Microscopy (SEM) is a powerful tool for the microstructural and crystallographic characterization of a wide range of materials.

The investigation by EBSD technique of such films presents some challenges since this analysis requires a flat and smooth surface. This is a necessary condition to avoid any shadow effects during the experiments performed with high tilting conditions (70º). This is also essential to ensure a good control of the three dimensional projection of the crystalline axes on the geometrical references related to the sample.

Crystalline texture is described by the inverse pole figure (IPF) maps (Figure 1). Through EBSD analysis it was observed that the external surface of the film presents a strong texture on the basal plane orientation (grains highlighted in red colour). Furthermore it was possible to verify that the grain size strongly depends on the deposition time (Figure 1 (a) and (b)). The electrical and optical film properties improve with increasing of the grain size, which can be mainly, attributed to the decrease in scattering grain boundaries which leads to an increasing in carrier mobility (Figure 2).

The authors kindly acknowledge the financial support from the Portuguese Foundation for Science and Technology (FCT) scientific program for the National Network of Electron Microscopy (RNME) EDE/1511/RME/2005.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

One way to improve the photophysical and photochemical properties of NIR probes is to incorporate them in nanoparticles (NPs). The characteristics of NP-based imaging agents, such as the ability to carry large payloads of optical probes and multiple targeting groups, together with the possibility to tune their pharmacokinetics, have motivated the development of different systems for use in combined diagnostic and therapeutic (theranostic) applications. The use of silica nanoparticles (SiNP) in nanomedicine, as carriers for drug delivery and imaging agents has increase remarkably in the last decade. On the other hand, it is well known that the use of near infrared (NIR) light (750-1400 nm) in optical bioimaging presents several advantages over lower wavelength light (visible), namely higher tissue penetration, lower interference from autofluorescence in biological specimens, and reduced light scattering. These factors have greatly increased the interest in NIR fluorescent dyes for use in biological imaging. An additional advantage of NIR dyes is that they can be used with inexpensive laser diode excitation sources in laser scanning microscopy.

In this communication we evaluate the performance of new fluorescent SiNP in laser scanning microscopy. The particles are labelled with two different perylenediimide (PDI) derivatives, one with emission in the visible region of the spectrum (PDIvis) and the other emitting in the NIR (PDInir). The PDI derivatives were covalently incorporated in the SiNPs during their synthesis by a modified Stöber method. The labelled SiNP were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), fluorescence emission spectroscopy and laser scanning fluorescence confocal microscopy (LSFCM).

The excellent photophysical properties and stability of the fluorescently labelled SiNP encouraged us to evaluate their performance in vivo, as markers for LSFCM. The nanoparticles were internalized in HEK293 cells co-stained with plasma membrane (AF594-WGA) and/or nucleus (Hoechst 33258) markers. Confocal microscopy images show that both SiNP-PDInir and SiNP-PDIvis were efficiently internalized in the cells (Figure 1 and 2, respectively). The major difference between the two sets of SiNPs is that while SiNP-PDIvis is excited at 488 nm (argon laser) showing emission in the green region of the spectra, SiNP-PDInir can be excited at 633 nm (using a low power/low cost HeNe laser) with the emission observed in the NIR. The in vivo photostability of the labelled nanoparticles was compared with that of a commercial membrane marker, DiIC18(5), showing much higher photostability during laser scanning, due to the shielding effect of the silica nanoparticles.

This work was partially supported by Fundação para a Ciência e a Tecnologia (FCT-Portugal) and COMPETE (FEDER) within projects PTDC/CTM/101627/2008 and PEst-OE/CTM/LA0024/2011. T.R., R.S. and F.F. also thank FCT for Ph.D. (SFRH/BD/64702/2009) and Pos-Doc (SFRH/BPD/71249/2010; SFRH/BPD/64320/2009) grants.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Liposomes or lipid vesicles are self-closed structures formed by one or several concentric lipid bilayers with an aqueous phase inside, which may incorporate almost any molecule, namely proteins, hormones, enzymes, antibiotics, anticancer agents, antifungical agents, gene transfer agents, DNA, and whole viruses. Scientific evidences prove that unprotected liposomes containing drugs are easily released from the endoplasmic reticulum of the cell. To increase the vesicles lifetime and to activate a controlled drug release with an external stimulus, the vesicles immobilization on a surface and the factors which create conditions to the liposome rupture have to be analyzed. A number of studies have identified some of the critical stages of vesicle adsorption (adhesion), fusion, deformation, rupture, and spreading of the lipid bilayer. Nevertheless, the formation mechanisms of well-controlled continuous supported bilayers or adsorption of whole liposomes are still not fully understood. As yet it was demonstrated that a controlled adsorption of vesicles containing a small fraction of charged lipids occurs without rupture and their subsequent embedding in polyelectrolyte multilayer (PEM) films, meaning vesicles may be immobilized in an intact or slightly deformed state, which can act as drug reservoirs. Moreover, depending on the nature of the physicochemical conditions of the vesicle solution and the substrate surface, a flat lipid bilayer can be formed, known as supported lipid bilayers, which can incorporate membrane proteins and keep the native dynamics of the lipid bilayer mimicking a biological membrane. In this study, a layer of 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (DPPG) liposomes adsorbed onto PEMs cushions based on poly(ethylenimine) (PEI), poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) polyelectrolytes was analyzed by atomic force microscopy (AFM) technique in non-contact mode and quartz crystal microbalance (QCM).

Sequential heterostructures of Si/PEI(PSS/PAH)4 and Si/PAH, also designated cushions, were prepared onto silicon substrates using the layer-by-layer (LbL) technique with polyelectrolyte solutions of PEI, PSS and PAH of monomeric concentrations of 0.01M. Topographic images of 1×1μm2 area of Si/PAH/DPPG (Figure 1 a), and Si/PEI(PSS/PAH)4/DPPG (Figure 1 b) LbL films were acquired by AFM. The root mean square roughness (RMS) calculated from topographies data are listed in table I. As shown, when a DPPG layer is adsorbed onto Si/PAH the RMS keeps an approximately equal value meaning that the liposome disrupted and spread onto the surface forming a planar lipid bilayer. But when a DPPG layer is adsorbed onto Si/PEI(PSS/PAH)4 the RMS value doubled, indicating that the structural integrity of the liposomes is maintained, even though there has been any deformation during adsorption. The adsorbed amount of the two PEMs and DPPG-liposomes layers was measured using a QCM and is displayed in table I. The DPPG adsorbed amount obtained on the PAH cushion was approximately equal to a planar lipid bilayer, while the adsorption onto PEI(PSS/PAH)4 was higher than the predicted for a planar lipid bilayer. This behavior suggests that the DPPG liposomes on the second PEM remained intact during adsorption. Both confirm the AFM results. Therefore we conclude that the initial roughness of the surface is a primordial factor to determine the adsorption or not of intact vesicles.

The authors acknowledge the “Fundação para a Ciência e Tecnologia” (FCT-MEC) by the post-graduate scholarship SFRH/BD/62229/2009 and the “Plurianual” funding.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Microstructural characterisation of an archaeological collection of Protohistoric bronze artefacts attributed to around the VIII century B.C. and has been carried out using optical microscopy (OM) and scanning electron microscopy combined with energy dispersive spectroscopy (SEM-EDS). The collection was found in Medronhal cave (Condeixa-a-Nova, Portugal) and is composed by 1 fibula, 5 bracelets and 31 rings.

Small areas on the surfaces of the artefacts were cleaned from corrosion and were metallographically prepared by a manual polishing with several diamond suspensions in a cotton swab until 1 micron diamond size. OM observations were performed in bright field (BF) illumination and under polarized light (Pol), in unetched and etched conditions. SEM-EDS was performed without a conductive coating for a minimum external elemental interference.

OM observations allowed the study of the method and sequence of manufacture involved in the production of the various types of artefacts. Results show that the fibula and the bracelets have equiaxed (recrystallised) grain structures resulting from cyclic thermo-mechanical treatments performed to a pre-form cast bar until requested shape and surface finishing was attained. The rings, which are of diverse sizes, have various types of microstructures as a result of diverse manufacturing techniques. Some show a dendritic structure that resulted from the casting, and others show recrystallised structures that resulted from cycles of deformation and annealing procedures posterior to their casting (Figure 1).

SEM-EDS analysis allowed the study of the presence of inclusions in the metallic matrix and the study of corrosion in some artefacts (Figure 2). Different types of inclusions were identified, namely copper sulphides, tin oxide, and lead rich inclusions. Both copper sulphides and lead inclusions are commonly found in archaeological bronzes, and can be a result of copper ores impurities. Tin oxide, on the other hand, is not so common, and its presence can be understood as a result of preferential oxidation of tin regarding copper during a melting or alloying operation. The study of the interface alloy/corrosion showed the presence of chlorides in internal corrosion layers, which can probably be related to an aggressiveness of the burial environment.

This research work has been financed by the Portuguese Science Foundation (FCT) through the EarlyMetal project (PTDC/HIS-ARQ/110442/2008), the grant SFRH/BPD/73245/2010 (to EF) and the Strategic Project-LA25-2011-2012 (PEst-C/CTM/LA0025/2011) (to CENIMAT/I3N).

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Stony materials applied in the built environment interact with diverse pollutants and can originate INORGANIC neoformations that can contribute to depreciation of these materials.

Microscopy studies help to characterize the chemical and textural features of these neoformations hence contributing to the understanding of the decay processes. In a study of diverse modern constructions in towns of Northern and Central Portugal were identified diverse neoformation substances in stony materials that were sampled and subjected to scanning electron microscopy (SEM) studies. While, in a strict perspective, implying destructive procedures that require the removal of a sample, microscopy techniques require minute amounts and can study occurrences of neoformations that can be detected at the macroscopic level. Products clearly resulting of metals corrosion were not considered in this study.

The dominant inorganic coatings and stains in the studied constructions are carbonate-rich whitish ones that can present diverse morphological features. Some of these carbonate-rich coatings have showed textural features defining a kind of urban travertine and the existence of several layers suggesting diverse episodes of solutions circulation and crystals precipitation, indicating the recurrence of the neoformation processes. Phosphates aggregates were also detected in several built surfaces, including indoor areas (Figure 1a,b). Another relatively common occurrence are efflorescences of more soluble salts, dominated by alkaline sulphates and carbonates (especially sodium sulphate) but were other salts such as alkaline nitrates (Figure 1c,d) and chlorides and magnesium sulphates have also been occasionally found. In some buildings it was possible to observe black crusts resulting from the fixation of atmospheric particles by gypsum aggregates. A very rare neoformation are silica-rich stains that in the situation presented in Figure 1e,f occur associate with calcium carbonate stains and metal corrosion products. The observed neoformations show a great geochemical and textural diversity in the surfaces of stony materials of modern built works, being evidences of diverse possible pollution sources that can interact under variable environmental conditions. Besides an important role that seems to be attributable to mortars materials (namely in relation to calcium carbonates and alkaline sulphates but that might also be the case for the phosphates in inside portions), there are also possible contributions from atmospheric pollutions (in the case of the black crusts) and the presence of alkaline nitrates could be indicative of organic sources as this connection is well established in older works. It has been admitted that alkaline nitrates in these modern works could either represent the persistence of contamination conditions from the past in the soils or the recurrence of the same polluting conditions. Also of particular interest are the textural informations indicating recurrence of neoformation episodes (relevant for possible cleaning interventions) and the chemical associations observed even in some very small samples.

The author acknowledges the support of the Fundação para a Ciência e Tecnologia (PEST-OE/CTE/UI0697/2011, funding by the national budget of the Portuguese Republic).

Salt weathering is one of the main processes affecting rock materials applied in the built environment. Scanning electron microscopy (SEM) studies can contribute to the understanding of the susceptibility of petrographic features of rocks to salt weathering.

SEM studies were performed in limestones (grainstones with the commercial designations of Semi-rijo and Moca Creme and a travertine) submitted to salt weathering tests (EN 12370 using sodium sulphate solutions and cubic specimens) consisting of 15 cycles of immersion/drying followed by water washing after the 15th cycle. Fragments from small cubes of the grainstones subjected to salt weathering cycles without the final water cleaning were also studied. SEM observation before and after the tests allows the discussion of the petrographical characteristics of these rocks that contribute to erosive decay under salt weathering.

In the case of the grainstones specimens the texture can be described in general as allochemical particles cemented by sparry calcite (Figure 1 a) and it is visible from the preparation of the polished surfaces the interface between the sparry cement and the allochemical components. After the salt weathering tests, SEM studies show (Figure 1 b) extensive fissuring in the sparry cement and separation between grains and sparry cement. Observations of disaggregation products showed an important amount of apparently intact grains. These results are similar to those observed by with the sparry cement being affect by salt crystallisation and lesser impact on the grains. Studies in the unwashed specimens showed the presence of sodium sulphate in the interface between allochemical grains and the sparry cement (Figure 1 c,d). Travertine specimens show heterogeneous patterns of erosion attributed to the heterogeneous texture of this rock, with more terrigenous (especially clay-rich) portions that favour a higher erosive susceptibility and the presence of clays has been frequently connected with salt weathering susceptibility in limestones. In Figure 1e can be observed the heterogeneity of a polished surface, with the more irregular portions showing a chemical spectra (Figure 1 f) indicative of the terrigenous component and the presence of sodium and sulphate (resulting from the solutions used in these weathering tests).

The authors acknowledge the support of the Fundação para a Ciência e Tecnologia (POCTI/CTA/44940/2002; PEst-OE/CTE/UI0697/2011 and Pest-OE/CTE/UI0098/2011, funding by the European Union and national budget of the Portuguese Republic). Acknowledgments to Eng. Teresa Luís, Eng. Sónia Pereira and Enterprise Mármores Galrão for the rock blocks.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

There are several problems regarding the dating of the works in the historical buildings (see a review in Sanjurjo-Sánchez, 2012). Mortars are a potential material for dating of the built environment works, being ubiquitous and not reusable. Optical stimulated luminescence (OSL) dating can be applied to mortars with and without lime and considering the age interval of mortars from thousands of years up to a few decades. OSL dating is based on measuring the accumulated luminescence signal of aliquots (of one or more mineral grains) of constituents from the mortars, resulting from the absorbed dose of surrounding radioactivity (at a constant dose rate), considering contributions both from environment and the radioactive phases of the mortars.

In this abstract is considered the relevance of microscopy studies as support for the preparation of samples for dating and the precise age calculations.

Microscopy studies can allow identifying samples that cannot be dated due to lack of enough grains of suitable phases as is illustrated in Figure 1a. It is also possible to assess the presence of datable phases. Usually quartz and potassium (K) feldspar are used for dating (phases that can be easily distinguished by scanning electron microscopy and generally by polarizing optical microscopy). For dating, the OSL signal of such datable phases of a mortar must have been bleached before the mortar manufacture and settling, typically by daylight exposure of such minerals. Quartz grains have an easy to bleach signal. K-feldspars grains have a significant internal dose making them less susceptible to environmental variations but they present signal anomalous fading and the luminescence signal is harder to bleach than in quartz grains. However, according to Li B. et al., 2007, the effect of anomalous fading in K-feldspar may be negligible for samples younger than 100 years and there also some proposals for overcoming signal fading and the combination of measurements on K-feldspars and quartz. On the preparation of the sample, microscopy studies can assess the risk of contamination by other phases and, in analogy with what is done in mining studies, define a liberation size that relates to the obtainment of monomineral aliquots. It can also contribute to the identification of the presence of different grainsize fractions of the phases to use in dating (see example in Figure 1b), information that can be used for comparative studies of dose in the different grainsize fractions, such as isochron measurement procedures. One of the main issues for dating is the assessment of the radioactive dose rate that affected the mortar constituents related to the distribution of the contents of U, Th, Rb and K that can occur disperse through the sample or concentrated on some grains. Most OSL studies on sediments relate K content to K-feldspar occurrences. However, in some mortars there could be an important presence of K-micas such as muscovite and the biotite series (see Figure 1b,c) that have a lower K content and a different morphology. The presence of these mica grains has also been considered as potentially disturbing of the signal measurements and procedures for its removal have been proposed by Kortekaas and Murray, 2005. The grainsize distributions of radioactive grains and dated grains can also affect the way the radioactive dose affect the measured dose given that the same amount of K could be distributed in grains with different volume and hence different relation area/mass. Additionally, K-bearing phases can have contents of other radioactive elements affecting the beta dose as is illustrated by Figure 1c showing the presence of halos resulting from radioactive decay of inclusions in biotite crystals. While in general it is admitted that quartz grains had a zero internal dose, the presence of inclusions such as rutile (that can be assessed by optical microscopy) can endanger this assumption. Microscopy studies can also be used to assess precipitation and dissolution process that occur after the preparation of the mortar and that can affect the beta dose for the grains (see Figure 1d). Finally, microscopy studies can be used after dose estimates and can help solve problems that have baffled researchers such as low content of feldspar separations. In the case of mortar samples, for which can be obtained representative sections, the previous considerations show that petrographic models can help in the definition of spatial models for dose rate modelling and the establishment of appropriated age models.

Support from Portuguese-Spanish collaboration Project “Ação Integrada E-141/10” (Fundação das Universidades Portuguesas)/“Acción Integrada PT2009-0077” (Ministerio de Ciencia e Innovación) and the Fundação para a Ciência e Tecnologia (pluriannual funding program for research units, PEst-OE/CTE/UI0697/2011, Portuguese funds).

Solid oxide fuel cells (SOFCs) are devices that allow direct conversion of chemical to electrical energy through an electrochemical reaction in a cleaner and more efficient way than conventional processes (eg. gas turbines). They are characterized by the use of a solid oxide material as the electrolyte. Yttria-stabilised zirconia (YSZ) has traditionally been used in SOFCs electrolytes at temperatures in the range of 850-1000 °C. Recent research is being focused on the development of new materials with increased ionic conductivity at intermediate temperatures (500-800ºC) as alternative materials to YSZ. Rare earth silicates with an apatite-type structure, such as doped lanthanum oxides of general formula La10(MO4)6O2, where M = Ge, Co, Si, Al, or P, are among these materials. The major limitation associated with the manufacture of these materials is their poor sinterability, which requires high sintering temperatures (1600ºC).

The present work concerns the production of La9.33Si2Ge4O26 dense materials from La2O3 (99.9%), SiO2 (99.4%) and GeO2 (99.9%) powders by mechanical alloying (MA) followed by conventional and microwave hybrid sintering at 1350ºC. Dry mechanical milling was carried out in protective atmosphere (argon at 200 kPa) by using a rotating speed of 350 rpm for 15h. Prior to the synthesis of the La9.33Si2Ge4O26 mixture, the starting materials were milled separately at 350 rpm in argon at 50 kPa in order to achieve low particle size distributions with a greater ability for sintering. The MA mixture was compacted by uniaxial pressing at 390 MPa followed by sintering for 1 h at 1350 °C. Density of the La9.33Si2Ge4O26 pellets was determined by the boiling test method. SEM/EDS, XRD and atomic force microscopy (AFM) were used for samples characterization.

The bulk densities and the open porosities of the pellets (EF and MW for conventional and microwave hybrid sintering, respectively) are presented in Table 1. Dense pellets were obtained in both cases. However, sample MW showed higher density and, consequently, lower porosity than sample EF. Both mechanically alloyed samples are formed by an apatite phase. This phase remains stable during sintering. However, traces of a second phase (La4GeO8) were detected after sintering. This phase was already referred in previous work (Serra et al., 2012). Figure 1 shows the morphology of the two samples obtained by SEM and AFM as well as the corresponding particles size distributions. The sintered samples were as-polished and thermal etched in air at 1300 ºC, for 10 min., for detailed microstructural observation. SEM images at low amplification confirm that sample EF is more porous than sample MW (Figure 1 (a) and (b), respectively). Although the same sintering temperature was used in both sintering processes, sample MW has a coarser grain size (Figure 1 (c) to (f)). This feature was already been reported in previous work (Fang et al., 1994). Mean values of 0.9 and 1.9 m were determined for samples EF and MW, respectively.

As conclusion, one may say that microwave hybrid sintering is a novel suitable process for the densification of La9.33Si2Ge4O26 powders for application in SOFCs electrolytes.

This research is partially sponsored by FEDER funds through the program COMPETE – Programa Operacional Factores de Competitividade – and by national funds through FCT – Fundação para a Ciência e Tecnologia – under the contract PTDC/EME-PME/102837/2008. The research fellowships granted to Cátia Alves, Márcio Santos and Mafalda Macatrão are also gratefully acknowledged.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Developing methods for immobilizing metallic nanoparticles (NP) onto different surfaces is a subject of fundamental interest, as nanometric structures enable the appearance of novel properties, absent in bulk or even in micrometric dimensions. In fact, the presence of NP with different size and shape on surfaces can induce substantial modifications on their electronic, optical, magnetic, physical or chemical proprieties. This will be very useful for many applications in different areas ranging from electronics to biomedicine.

In this work, we use a simple, reproducible and economic method to grow metallic gold and silver NP directly on cellulose surfaces. A prior chemical activation of the alcohol groups on the cellulose surface is needed for grafting amino functions, which will complex silver and gold ions. Therefore, NP nucleation is only allowed and selectively accomplished on these seed coordination sites. The growth of NP is achieved by the interaction of aqueous dilute solutions of AgNO3 or NaAuCl4 with the cellulose surface. The procedure limits the generation of NP only to the cellulose surface, keeping the dispersion medium completely exempt of them. The resulting NP are, consequently chemically immobilized on the cellulose surface. The chemical anchoring of the NP to the surface avoids particle desorption and extends the lifetime of the resulting hybrid materials. Following this procedure, silver and gold NP could be successfully created on cellulose and this was supported by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM).

The present AFM (Figure 1) study enabled to characterize the size and shape of silver NP: they are spherical and have a diameter of ~15 nm. SEM image of Ag NP (Figure 2) display the existence of NP agglomerates. Comparison of the two images suggests size and spatial distributions strongly non- uniform. It is now a challenge to deposit nanoparticles in an organized manner, achieving a regular surface functionalization of cellulose. In TEM (Figure 3) we see a sample where Ag and Au salts interacted simultaneously with the cellulose surface. Crossing the images with other information from analytical techniques, it seems that Ag NP and Au NP form mainly separately instead of presenting a core-shell structure. Also, there is evidence that larger NP are the ones made of silver which suggests that the final result is kinetically (and not thermodynamically) controlled.

The authors acknowledge FCT for A.M. Ferraria Grant SFRH/BPD/26239/2006, for A. P. Carapeto Grant SFRH/BD/75734/2011 and strategic projects PEst-OE/CTM/LA0024/2011 and PEst-OE/CTM-UI0084/2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.