Small-angle X-ray Scattering Measurements Research Articles

Structure of Micelles Calcium Didodecyl Sulfate: A SAXS Study

This paper reports the structure of micelles of Calcium Didodecyl Sulfate (CDS), Ca(DS)2 , as studied using Small Angle X-ray Scattering (SAXS). CDS is a dianionic surfactant consisting of two DS- tails attached to Ca++ divalent ion. There is considerable interest in understanding the structure (especially the outer shell of counter-ions) of micelles of CDS as unlike conventional surfactants (e.g. CTAB, SDS) where counter-ion is monovalent, CDS has a divalent counter-ion. SAXS is an ideal technique for obtaining information about the outer shell of the Ca(DS)2 micelle, as the constituents (S, Ca, O etc.) of the shell are strong X-ray scatterers. The SAXS measurements have been made on salt-free aqueous solutions of calcium didodecyl sulfate for surfactant concentrations of 0.5, 1.0, 2.5, and 20 weight % (or 8.8, 17.7, 44.92 and 438.01 mM/dm3 ) respectively. Single step indirect Fourier transformation method has been utilized to generate particle distance distribution function. It is found that micelles are prolate ellipsoidal in shape. The size parameters of the ellipsoidal micelles have been determined. Other relevant parameters like mean aggregation number and effective fractional charge has been determined by fitting an ellipsoidal shaped core-shell model to the Fourier transformed scattering data. It is seen that increase in surfactant concentration results in lowering of aggregation number, increase of shell thickness and lowering of total charge and probably lowering of water association.

Influence of Nanosize Silica Particles on the Rheological Behaviour of Lyotropic Cubic Phase of Glucopone (APG) Surfactant

The effect of nanosize silica particle on the stability, structures and rheological behaviours of cubic liquid crystalline phases of Glucopone/water/heptane system were investigated. Small-angle X-ray scattering (SAXS) and polarizing microscope were used for phase identification and structure characterization. SAXS scattering profile was characteristic to cubic phase before and after the addition of silica particles. The cubic samples showed several diffraction peaks and can be assigned to the Ia3d space group. The area per surfactant molecule was found to increase as the silica concentrations was increased. Moreover, the rheological study on the cubic phase with different silica concentration was performed. The frequency-dependent storage and loss modulus were found to be characteristic of the cubic phase in the linear viscoelastic region. The cubic samples behave as solid-like material with storage modulus G’~ 0.7106 Pa typical of cubic lyotropic materials. The elasticity of cubic samples was found to increase with silica concentration. The increase in the elasticity was ascribed to the network and the formation of smaller structure as indicated by SAXS measurements. As temperature was further increased a decreased in the elasticity was observed confirming the structural change as indicated by the change in slopes of G’ and G”. The cubic samples exhibited shear thinning behaviours, with the dynamic viscosity being affected by the silica particles concentrations and the effect of silica particles on the rheological behaviours was quite noticeable as the concentration increased. The results showed strong correlation between rheology and microstructural changes in the dispersion of nanoparticle silica in the cubic phase system.

Bismuth nanoparticles synthesized by laser ablation in lubricant oils for tribological tests

The improvement of the tribological properties of mineral base oils through the addition of bismuth nanoparticles as an additive, together with the idea of obtaining lubricants free of heavy metals, was evaluated. Bismuth nanoparticles were produced directly in the heavy and light viscosity mineral base oils (BS900 and BS6500) using the technique of laser ablation of solids immersed in liquids. Transmission electron microscopy measurements showed the presence of pure bismuth nanoparticles. Small Angle X-ray Scattering (SAXS) measurements showed that the average size of the nanoparticles was between 7 and 65nm depending on the experimental conditions used. The tribological properties of the base oil with the bismuth nanoparticles additives were evaluated using a four-ball tester. Tests were performed using the base oil with and without Bi nanoparticles. It was observed that the coefficient of friction of the oil decrease with an increasing concentration of the nanoparticles. The results also showed that the wear rate was reduced when the Bi nanoparticle additives were used.

<i>In Situ</i> Synchrotron SAXS/WAXD Study during Uniaxial Drawing of Poly (L-Lactic Acid)

The structure development of poly (L-lactic acid)(PLLA) during the uniaxial drawing was investigated by means of in-situ simultaneous wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements. When the quenched amorphous film of PLLA was drawn at 77.2 oC, which was well above the glass transition temperature of PLLA, two different crystal structures were formed depending on the strain. The mesophase, which has 103 helix with large amount of packing disorder, was formed at the early stage of drawing, followed by the crystal transformation into α’ form (ε ≥ 1.5). SAXS measurement showed that the kebab formation begins at the stage later than that of meso-α’ transition. It strongly suggests that the transition takes place inside the shish structure. The development of kebab leads to the enhancement of mechanical response, which is found to be the origin of the strain hardening of PLLA.

Intercalation of cellulase enzyme into a hydrotalcite layer structure

A new inorganic–organic hybrid material whereby cellulase enzyme is incorporated into a hydrotalcite type layered double hydroxide (LDH) structure is reported. The Mg2Al–cellulase–LDH was synthesized via co-precipitation from Mg/Al nitrate at pH=9.6. Characterization was performed using X-ray powder diffraction (XRD), small angle X-ray scattering (SAXS), elemental analysis, infrared spectroscopy (IR) and thermogravimetry (TG). From XRD and SAXS measurements, a d-value of ~5.0nm was identified for the basal spacing of the Mg2Al–cellulase–LDH. Consequently, the cellulase enzyme (hydrodynamic diameter ~6.6nm) attains a slightly compressed conformation when intercalated.Formation of the LDH hybrid was also confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mg2Al–cellulase–LDH phases appear as ~20nm thin foils which are intergrown to flower-like aggregates. Activity of the enzyme was retained after deintercalation from the Mg2Al–LDH framework using anion exchange. Accordingly, cellulase is not denatured during the intercalation process, and LDH presents a suitable host structure for time-controlled release of the biomolecule.

Weak self-interactions of globular proteins studied by small-angle X-ray scattering and structure-based modeling.

We investigate protein-protein interactions in solution by small-angle X-ray scattering (SAXS) and theoretical modeling. The structure factor for solutions of bovine pancreatic trypsin inhibitor (BPTI), myoglobin (Mb), and intestinal fatty acid-binding protein (IFABP) is determined from SAXS measurements at multiple concentrations, from Monte Carlo simulations with a coarse-grained structure-based interaction model, and from analytic approximate solutions of two idealized colloidal interaction models without adjustable parameters. By combining these approaches, we find that the structure factor is essentially determined by hard-core and screened electrostatic interactions. Other soft short-ranged interactions (van der Waals and solvation-related) are either individually insignificant or tend to cancel out. The structure factor is also not significantly affected by charge fluctuations. For Mb and IFABP, with a small net charge and relatively symmetric charge distribution, the structure factor is well described by a hard-sphere model. For BPTI, with a larger net charge, screened electrostatic repulsion is also important, but the asymmetry of the charge distribution reduces the repulsion from that predicted by a charged hard-sphere model with the same net charge. Such charge asymmetry may also amplify the effect of shape asymmetry on the protein-protein potential of mean force.

Labeling phospholipid membranes with lipid mimetic luminescent metal complexes

Lipid-mimetic metallosurfactant based luminophores are promising candidates for labeling phospholipid membranes without altering their biophysical characteristics. The metallosurfactants studied exhibit high structural and physicochemical similarity to phospholipid molecules, designed to incorporate into the membrane structure without the need for covalent attachment to a lipid molecule. In this work, two lipid-mimetic phosphorescent metal complexes are described: [Ru(bpy)2(dn-bpy)]2+ and [Ir(ppy)2(dn-bpy)]+ where bpy is 2,2′-bipyridine, dn-bpy is 4,4′-dinonyl-2,2′-bipyridine and ppy is 2-phenylpyridine. Apart from being lipid-mimetic in size, shape and physical properties, both complexes exhibit intense photoluminescence and enhanced photostability compared with conventional organic fluorophores, allowing for prolonged observation. Moreover, the large Stokes shift and long luminescence lifetime associated with these complexes make them more suitable for spectroscopic studies. The complexes are easily incorporated into dimyristoil-phosphatidyl-choline (DMPC) liposomes by mixing in the organic solvent phase. DLS reveals the labeled membranes form liposomes of similar size to that of neat DMPC membrane. Synchrotron Small-Angle X-ray Scattering (SAXS) measurements confirmed that up to 5% of either complex could be incorporated into DMPC membranes without producing any structural changes in the membrane. Fluorescence microscopy reveals that 0.5% label content is sufficient for imaging. Atomic Force Microscopic imaging confirms that liposomes of the labeled bilayers on a mica surface can fuse into a flat lamellar membrane that is morphologically identical to neat lipid membranes. These results demonstrate the potential of such lipid-mimetic luminescent metal complexes as a new class of labels for imaging lipid membranes.

Effect of metal oxide on surface area and pore size of water-dispersible colloids from three German silt loam topsoils

The surface area and pore structure of easily dispersed soil particles <2μm in size (water-dispersible colloids, WDCs) are important for carbon sequestration and transport in soil, two processes which are essential for the terrestrial carbon cycling. In this work, we determine the effects of dithionite–citrate–bicarbonate (DCB) extractable metal oxides, and oxalate extractable metal oxides on the specific surface area (SSA) and pore structure of WDCs from silt loam topsoils of three TERENO test sites with a similar clay content (20%) in Germany (arable (Selhausen), grassland (Rollesbroich) and forest (Wuestebach) soils). The N2 gas-adsorption (−196°C), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and microelectrophoretic (ME) methods were used and compared. Results show that 1) the SSA of the WDCs from Selhausen, Rollesbroich, and Wuestebach decreased more after DCB treatment (27%, 35%, and 44%) than after oxalate treatment (5%, 14%, and 22%). DCB removed metal oxide nanoparticles from WDCs were found to have diameters (dp) ranging from 4nm to 8nm and the surface loading ratios on the surface of aluminosilicate residues in WDCs were estimated to be 11% to 22% for three soils where the highest value was found in the acidic forest soil. 2) Pore sizes in the mesopore range (2nm to 50nm) were analyzed in the WDC fractions. The results were discussed in terms of accessible open pores for the pristine WDCs and WDC samples from which metal oxide nanoparticles and organic carbon (OC) had been removed. The lower average pore radius (Rp) measured by the N2 gas-adsorption method based on the total volume (Vt) to SSA ratio variations in WDCs without metal oxides compared to WDC with metal oxides indicated a contraction of the porous structure of WDCs due to the presence of metal oxide nanoparticles. The pore size distribution (PSD) analysis showed a sensitive contribution of metal oxide nanoparticles in the low range of pore sizes (<25nm) of WDCs. In SAXS measurements, higher surface fractal dimensions (Ds) were observed in WDCs before the metal oxide's removal, which supports a roughness increase of the interfaces in the presence of nanoparticles. The colloidal characterization of WDCs by the DLS and ME methods shows, at a μm scale, the role of positively charged metal oxide nanoparticles in forming WDCs with a more compact structure by decreasing the particle size (dz) and the negative zeta potential (ζ). 3) The comparison of Rp, k, dz and dp results between different soils also indicates the dependence on the clay mineralogy of WDCs so that the heterocoagulation between kaolinite and illite (clay minerals of different aspect ratios) increases the size of soil mesopores (Rollesbroich). In conclusion, the results of this study clearly show that the combination of the N2 gas-adsorption, SAXS, DLS and ME methods allows the characterization of soil porosity in the nanometer range where metal oxide nanoparticles contribute to a more compact structure of WDC.

Effects of ultrasound on cross-flow ultrafiltration of skim milk: Characterization from macro-scale to nano-scale

This study investigates effects of ultrasound (US) on cross-flow ultrafiltration of skim milk by multi-scale characterization, using a custom designed “SAXS Cross-Flow US-coupled Filtration Cell”. The study of flow properties of casein micelle suspensions shows an evolution of their rheological behavior from Newtonian to shear-thinning until the emergence of yield stress with the increase of concentration (from 27gL−1 to 216gL−1). The concentration profiles during cross-flow filtration of skim milk have been revealed for the first time by real-time in-situ Small Angle X-ray Scattering (SAXS) measurement. Without any change of internal structure of casein micelles and membrane selectivity, the applied ultrasound (20kHz, 2Wcm−2) leads to a significant increase of permeate flux arising from a disruption of concentrated layer. Varying the US intensity from 0.6Wcm−2 to 2.9Wcm−2 does not affect the US enhancement factor, which however depends on the feed concentration. In fact, increase of feed concentration induces the formation of highly cohesive fouling layer during filtration that the applied US could hardly disrupt. Results also suggest that the preventive US application mode is promising since formation of the reversible fouling layer was strongly limited in this mode.

Hybrid silica generated In situ in polyurethane‐based composites

ABSTRACTA series of composites of commercial polyurethane (PU) and hybrid silica have been prepared by the sol‐gel process through the in situ synthesis of hybrid silica in a solution of dichloromethane. Mechanical properties, small angle x‐ray scattering (SAXS) and differential scanning calorimetry measurements were performed to evaluate the effects that hybrid silica has on the properties of the resulting PU composites. A series of 13 different organosilane differing in polarity and alkyl chain length has been employed. Compared with pristine PU, composites bearing hybrid silicas were more likely to exhibit reductions in the yield stress and increase in the elongation at break. Samples also showed a negligible variation in the glass transition temperature and a reduction in the ΔCp. The enthalpy of the crystallization process showed a trend towards reduction. Based on the SAXS measurements, the composites showed a small reduction in the interdomain spacing, an increase in the degree of phase separation and a tendency towards reduction in the size of the interphase thickness between domains. These results can be better explained as being caused by the volume of the organic group from the organosilane rather than by the chemical interaction of the organic group with the PU organic moieties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41157.

Precipitate evolution in the early stages of ageing in Inconel 718 investigated using small-angle x-ray scattering

Microstructural evolution during the early stages of ageing (less than one hour) in a Ni–Cr–Fe based superalloy Inconel 718 (IN718) has been investigated using Small-Angle X-ray Scattering (SAXS). The effects of precipitate kinetics on the precipitate size distribution are compared indirectly with SAXS measurements by using Vickers microhardness data. The microhardness increased after 4min of ageing at a temperature of 760°C, although the recorded SAXS data did not reveal the precipitate size distribution. This indicates that the precipitates had not evolved enough to be detected, but still a small number of precipitates increased the yield strength. After ageing the alloy for the shortest period for which data were available, 8min, clear evidence of precipitates could be found from the SAXS data, showing that the γ″- precipitates are about 6nm in width and 3nm in height.

Absolute scale calibration with use of excess scattering length for small-angle X-ray scattering

For small-angle X-ray scattering (SAXS) in solution, absolute intensity calibration is an important step to estimate the number of electrons of the sample. In this study, the excess scattering length of 1-bromododecane dispersed in dodecane was determined using that of 1-chlorododecane in the same solvent. The deviation of the experimental values from theoretical calculations obtained using atomic factors was around 1%. It is suggested that the 1-chlorododecane–dodecane system constitutes a new calibration approach that is applicable to various materials over a large energy range generally used in SAXS measurements, and could be less complex and more reliable than conventional methods.

Evolution of Helium with Temperature in Neutron-Irradiated10B-Doped Aluminum by Small-Angle X-Ray Scattering

Helium status is the primary effect of material properties under radiation.10B-doped aluminum samples were prepared via arc melting technique and rapidly cooled with liquid nitrogen to increase the boron concentration during the formation of compounds. An accumulated helium concentration of ~6.2 × 1025 m−3was obtained via reactor neutron irradiation with the reaction of10B(n,α)7Li. Temperature-stimulated helium evolution was observed via small-angle X-ray scattering (SAXS) and was confirmed via transmission electron microscopy (TEM). The SAXS results show that the volume fraction of helium bubbles significantly increased with temperature. The amount of helium bubbles reached its maximum at 600°C, and the most probable diameter of the helium bubbles increased with temperature until 14.6 nm at 700°C. A similar size distribution of helium bubbles was obtained via TEM after in situ SAXS measurement at 700°C, except that the most probable diameter was 3.9 nm smaller.

Critical Exponents for Solvent Extraction Resolved Using SAXS

The solvent extraction of an ionizable solute (H3PO4) from water into a water-in-oil microemulsion, and subsequent organic phase splitting (known as third phase formation), has been recast as a critical phenomenon by linking system structure to solute concentration via a critical exponent. The transuranic extraction (TRUEX) system was investigated by extracting increasing concentrations of H3PO4 into a microemulsion--consisting of two extractant amphiphiles (CMPO and TBP) and water in n-dodecane--and taking small-angle X-ray scattering (SAXS) measurements from the resulting solutions. The H3PO4 concentration at which phase splitting occurred was defined as the critical concentration (XC), and this was related to the precritical concentrations (X) by the reduced parameter ε = (X(C) - X)/X(C). The scattering intensity at the zero angle I(0), relating to the interaction between reverse micellar aggregates, conformed to the relation I(0) = I0ε(-γ), with critical exponent γ = 2.20. To check γ, SAXS measurements were taken from the organic phase in situ with variable temperature through the point at which third phase formation initiates (the critical temperature), giving I(0) = I0t(-γ), where t = (T - T(C))/T(C) and T(C) and T are the critical and precritical temperatures, with critical exponent γ = 2.55. These γ values suggest third phase formation is a universal phenomenon manifest from a critical double point. Thus, solvent extraction is reduced to its fundamental physical roots where the system is not defined by detailed analysis of metrical properties but by linking the fundamental order to thermodynamic parameters via an exponent, working toward a more predictive understanding of third phase formation.

Growth and migration of nanocavities in He+ multi-implanted Si measured by in situ small-angle X-ray scattering

Abstract Multi-implantations of He ions were performed on Si samples with (111) or (100) surface orientation in the kiloelectron volt (keV) energy range. The fluencies were chosen to keep the local He concentration constant and above the threshold to get nanocavities upon annealing. Small-angle X-ray scattering (SAXS) experiments were carried out, for the first time ever, to follow in situ the evolution of the size distribution of nanocavities created in the Si bulk. The cavity distribution was measured in the as-implanted state and followed during annealing from 623 K up to 973 K. The final spatial distribution was obtained ex situ by transmission electron microscopy (TEM). Whatever the surface orientation, the increase of the porosity is triggered at 973 K which is a temperature at least 200 K higher than expected. This ongoing increase proves that the growth stage is not complete even after a 2-h annealing. The onset of a new nanocavity population in the (111) Si sample is an experimental evidence that the migration–coalescence (MC) process, although weak at such a low temperature range, contributes to the evolution of the nanocavity size. Basic mechanisms for the growth and coarsening of nanocavities/bubbles are discussed in view of the experimental data arising from in situ SAXS measurements coupled with ex situ TEM observations.

Isotropic/nematic and sol/gel transitions in aqueous suspensions of size selected nontronite NAu1

AbstractThe phase behaviour of aqueous suspensions of NAu1 nontronite was studied on size-selected particles by combining osmotic pressure measurements, visual observations under polarized light, rheological experiments and Small Angle X-ray Scattering (SAXS). NAu1 suspensions display a liquid crystalline behaviour as they exhibit a Isotropic/Nematic (I/N) transition that occurs before the sol/gel transition for ionic strengths below 10–3M/L. This I/N transition shifts towards lower volume fractions for increasing particle anisotropy and its position in the phase diagram agrees well with the theoretical predictions for platelets. SAXS measurements reveal the presence of characteristic interparticular distances in the isotropic, nematic and gel phases. In the gel phase a local lamellar order is observed which shows that the “house of cards” model is not appropriate for describing the gel structure in swelling clay materials at low ionic strength. Furthermore, by combining results from osmotic pressure measurements and X-ray scattering, it appears that the pressure of the system can be well described using a simple Poisson-Boltzmann treatment based on the repulsion between charged infinite parallel planes. In terms of rheological properties, even if the thermodynamical status of the sol/gel transition remains partially unclear, the yield stress and elasticity of the gels can be easily renormalized for all particle sizes on the basis of the volume of the particles. Furthermore, rheological modelling of the flow curves shows that for all the particles an approach based on excluded volume effects captures most features of nontronite suspensions.

A study of small angle X-ray scattering from impregnated activated carbons

A description of the incipient wetness or imbibing method of impregnating activated carbons with a variety of chemical species and at various mass loadings is given. Since the impregnants can be located in macro, meso and micropores, changes to small angle X-ray scattering (SAXS) patterns should occur as impregnant is loaded into activated carbon. Using a modified Kalliat model and suitable interpretation, calculations illustrate the impacts of micropore filling and impregnant micrograins within larger pores on the SAXS patterns. SAXS measurements on a given set of impregnated carbons were used to determine the micropore volume and impregnant filling fraction as well as the impregnant micrograin volume. SAXS is demonstrated to be a useful tool for examining the distribution of chemical impregnant in microporous carbon materials.

Microstructure determination of IQ-WB clays: a direct procedure by small-angle X-ray scattering

An accurate characterization of the microstructure of raw and pure homoionic clays from Wadi Bashira in Iraq (IQ-WB) has been carried out experimentally, using small-angle X-ray scattering (SAXS) and dynamic light scattering. The structures of lamellar IQ-WB dispersions were identified by these techniques and by complementary free swelling and dialysis experiments. SAXS measurements were used to resolve the characteristic distance,hs, between individual platelets in Na IQ-WB and between platelets inside tactoids formed in Ca clays. The tactoids in raw and Ca IQ-WB have well formed lamellar structures wherehs= 1.9 nm. The average lateral size, 〈D〉, of a platelet is determined to be a few hundred nanometres. Analysis of the SAXS peaks, based on the Scherrer relation, revealed a small difference in the average number of platelets per tactoid, 〈N〉 = 6–9, depending on platelet size and the concentrations of divalent counter-ions. It was also found that the average tactoid size can be estimated from an empirical relation as follows: 〈N〉 ≃ δ + α〈D〉, where δ is a constant and α the slope.

Crystallization and melting of poly(glycerol adipate)‐based graft copolymers with single and double crystallizable side chains

ABSTRACTThe crystallization and melting behavior of a series of poly(glycerol adipate) (PGA) based graft copolymers with either poly(ε‐caprolactone) (PCL), poly(ethylene oxide) (PEO), or PCL‐b‐PEO diblock copolymer side chains (i.e., PGA‐g‐PCL, PGA‐g‐PEO, and PGA‐g‐(PCL‐b‐PEO)) was studied using polarized light optical microscopy (POM), differential scanning calorimetry (DSC), small‐angle X‐ray scattering (SAXS), and wide‐angle X‐ray diffraction (WAXD). These results were compared with the behavior of the corresponding linear analogs (PEO, PCL, and PCL‐b‐PEO). POM revealed that spherulitic morphology was retained after grafting. However, spherulite radius as well as radial growth rate was significantly smaller in the graft copolymers. Evaluation of isothermal crystallization kinetics by means of the Avrami theory revealed that the nucleation density was much higher in the graft copolymers. The DSC results indicated that the degree of crystallinity decreased strongly upon grafting while the melting temperatures of PGA‐g‐PCL and PGA‐g‐PEO were found to be close to the values of neat PCL and PEO, respectively. This was attributed to the absence of specific thermodynamic interactions, and, additionally, to lamella thicknesses being similar to those of the homopolymers. The latter point was confirmed by SAXS measurements. In case of PCL‐b‐PEO diblock copolymers and PGA‐g‐(PCL‐b‐PEO) graft copolymers, the crystallization behavior and thus the resulting lamellar morphology is more complex, and a suitable model was developed based on a combination of DSC, WAXD, and SAXS data. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1581–1591

Pore structure, interface properties and photocatalytic efficiency of hydration/dehydration derived TiO2/CNT composites

Manifold advantages are foreseen by using carbon nanotubes (CNTs) as support for inorganic TiO2 nanoparticles due to the unique texture/morphology and adsorption capacity of CNTs. Synergistic effects might also result from interfacial charge transfer between the CNTs and TiO2. Effective charge transfer has the potentiality to limit electron/hole recombination and shift the TiO2 photocatalytic response to the visible range. Homogeneous mixing and intimate contact between the graphitic and TiO2 surfaces are of high importance in order to trigger synergistic effects. Thus, the existence of complementary methods to shed light on both these features is of high importance when developing TiO2/CNT composite photocatalysts. In this work, a wide variety of TiO2/CNT composites was prepared by a simple hydration/dehydration procedure, using single-wall (SWCNTs) and multi-wall (MWCNTs) carbon nanotubes, either functionalized or not, and TiO2 nanoparticles of different size. To evaluate the degree of homogeneity between the graphitic and inorganic phases, a new methodology which was based on a complex interpretation of the liquid nitrogen porosimetry (LN2) isotherms of the composites and of each phase in the composite separately was developed. Furthermore, interface interaction characteristics were elucidated by micro-Raman spectroscopy while small-angle X-ray scattering (SAXS) measurements provided insight on the surface roughness and micropore structure of the TiO2/SWCNT samples. The Raman analysis concluded to the absence of any interfacial interaction. In this context the efficiency of the prepared composites to photocatalytically oxidize caffeine was evaluated in regard to their homogeneity, as derived by the LN2 method. As expected, in the absence of synergetic effects the photocatalytic efficiency correlated well with the extent of mixing between the CNTs and TiO2 phases. The discrepancy observed for one of the samples was attributed to the existence of large micropores, a feature that was distinguishable solely by SAXS measurements.