Nitrite anodic oxidation at Ni(II)/Ni(III)-decorated mesoporous SnO2 and its analytical applications.

Hydrothermally formed mesoporous SnO2 was used as a support for nickel chemical deposition and, after subsequent thermal treatment, a high specific surface area (36 m2 g-1) Ni/SnO2 material was obtained. XPS analysis has shown that in the Sn 3d region the spectrum is similar to that of pristine SnO2, whereas Ni species are present on the surface as NiO, Ni2O3 and Ni(OH)2. Mixing Ni/SnO2 with a small amount of Black Pearls (BP) leads to a significant enhancement of the resulting Ni/SnO2-BP composite activity for nitrite anodic oxidation, presumably due to the higher surface area (115 m2 g-1), to better electrical conductivity and to a certain contribution of the BP to an increase in surface density of the active sites. Ni/SnO2-BP also outperforms pristine BP (in terms of Tafel slopes and electron-transfer rates), most likely due to the fact that the Ni(II)/Ni(III) couple can act as an electrocatalyst for nitrite oxidation. A voltammetric method is proposed for the determination of nitrite, over a concentration range of three orders of magnitude (0.05 to 20 mM), with good reproducibility, high stability and excellent sensitivity. The high upper limit of the dynamic range of the analytically useful response might provide a basis for the reliable quantification of nitrite in wastewater.

Novel Antitumor Agents Based on Fluorescent Benzofurazan Derivatives and Mesoporous Silica.

Two novel fluorescent mesoporous silica-based hybrid materials were obtained through the covalent grafting of [4-hydrazinyl-7-nitrobenz-[2,1,3-d]-oxadiazole (NBDH) and N1-(7-nitrobenzo[c][1,2,5]-oxadiazol-4-yl) benzene-1,2-diamine (NBD-PD), respectively, inside the channels of mesoporous silica SBA-15. The presence of fluorescent organic compounds (nitrobenzofurazan derivatives) was confirmed by infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermal analysis (TG), and fluorescence spectroscopy. The nitrogen physisorption analysis showed that the nitrobenzofurazan derivatives were distributed uniformly on the internal surface of SBA-15, the immobilization process having a negligible effect on the structure of the support. Their antioxidant activity was studied by measuring the ability to reduce free radicals DPPH (free radical scavenging activity), in order to formulate potential applications of the materials obtained. Cytotoxicity of the newly synthesized materials, SBA-NBDH and SBA-NBD-PD, was evaluated on human B16 melanoma cells. The morphology of these cells, internalization and localization of the investigated materials in melanoma and fibroblast cells were examined through fluorescence imaging. The viability of B16 (3D) spheroids after treatment with SBA-NBDH and SBA-NBD-PD was evaluated using MTS assay. The results showed that both materials induced a selective antiproliferative effect, reducing to various degrees the viability of melanoma cells. The observed effect was enhanced with increasing concentration. SBA-NBD-PD exhibited a higher antitumor effect compared to SBA-NBDH starting with a concentration of 125 µg/mL. In both cases, a significantly more pronounced antiproliferative effect on tumor cells compared to normal cells was observed. The viability of B16 spheroids dropped by 40% after treatment with SBA-NBDH and SBA-NBD-PD at 500 µg/mL concentration, indicating a clear cytotoxic effect of the tested compounds. These results suggest that both newly synthesized biomaterials could be promising antitumor agents for applications in cancer therapy.

Antimicrobial Properties of TiO2 Microparticles Coated with Ca- and Cu-Based Composite Layers.

The ability of TiO2 to generate reactive oxygen species under UV radiation makes it an efficient candidate in antimicrobial studies. In this context, the preparation of TiO2 microparticles coated with Ca- and Cu-based composite layers over which Cu(II), Cu(I), and Cu(0) species were identified is presented here. The obtained materials were characterized by a wide range of analytical methods, such as X-ray diffraction, electron microscopy (TEM, SEM), X-ray photoelectron (XPS), and UV-VIS spectroscopy. The antimicrobial efficiency was evaluated using qualitative and quantitative standard methods and standard clinical microbial strains. A significant aspect of this composite is that the antimicrobial properties were evidenced both in the presence and absence of the light, as result of competition between photo and electrical effects. However, the antibacterial effect was similar in darkness and light for all samples. Because no photocatalytic properties were found in the absence of copper, the results sustain the antibacterial effect of the electric field (generated by the electrostatic potential of the composite layer) both under the dark and in light conditions. In this way, the composite layers supported on the TiO2 microparticles' surface can offer continuous antibacterial protection and do not require the presence of a permanent light source for activation. However, the antimicrobial effect in the dark is more significant and is considered to be the result of the electric field effect generated on the composite layer.

Physicochemical Characterization and Drug Release Properties of Methyl-Substituted Silica Xerogels Made Using Sol-Gel Process.

In this work, a multi-analytical approach involving nitrogen porosimetry, small angle neutron and X-ray scattering, Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, X-ray diffraction, thermal analysis and electron microscopy was applied to organically modified silica-based xerogels obtained through the sol-gel process. Starting from a tetraethoxysilane (TEOS) precursor, methyltriethoxysilane (MTES) was added to the reaction mixture at two different pH values (2.0 and 4.5) producing hybrid xerogels with different TEOS/MTES molar ratios. Significant differences in the structure were revealed in terms of the chemical composition of the silica network, hydrophilic/hydrophobic profile, particle dimension, pore shape/size and surface characteristics. The combined use of structural characterization methods allowed us to reveal a relation between the cavity dimensions, the synthesis pH value and the grade of methyl substitution. The effect of the structural properties on the controlled Captopril release efficiency has also been tested. This knowledge facilitates tailoring the pore network for specific usage in biological/medical applications. Knowledge on structural aspects, as reported in this work, represents a key starting point for the production of high-performance silica-based hybrid materials showing enhanced efficacy compared to bare silica prepared using only TEOS.

Sintered and 3D-Printed Bulks of MgB2-Based Materials with Antimicrobial Properties.

Pristine high-density bulk disks of MgB2 with added hexagonal BN (10 wt.%) were prepared using spark plasma sintering. The BN-added samples are machinable by chipping them into desired geometries. Complex shapes of different sizes can also be obtained by the 3D printing of polylactic acid filaments embedded with MgB2 powder particles (10 wt.%). Our present work aims to assess antimicrobial activity quantified as viable cells (CFU/mL) vs. time of sintered and 3D-printed materials. In vitro antimicrobial tests were performed against the bacterial strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Enterococcus faecium DSM 13590, and Enterococcus faecalis ATCC 29212; and the yeast strain Candida parapsilosis ATCC 22019. The antimicrobial effects were found to depend on the tested samples and microbes, with E. faecium being the most resistant and E. coli the most susceptible.

Electron paramagnetic resonance and microstructural insights into the thermal behavior of simonkolleite nanoplatelets.

The aim of this paper is the study of the thermal behavior of the simonkolleite Zn5(OH)8Cl2·H2O (ZHC) by electron paramagnetic resonance (EPR) spectroscopy, in particular. It is well known that during heating ZHC undergoes a complex transformation which involves several overlapping stages. However, with reference to the data reported on this subject, it can be concluded that there is still an ongoing debate regarding the intermediate stages of this process. The data presented in this study support a simple decomposition process of the ZHC prepared using the precipitation method. The EPR data correlated to the data obtained by other experimental techniques, such as XRD, TEM, SEM and EDX, indicate that during the thermal treatment the ZHC suffers a partial decomposition to ZnO with no intermediate products. After annealing at 500 °C for 1 h, a recombination process of ZHC is observed. Moreover, the kinetics associated to these decomposition steps were determined and the evolution of the paramagnetic centers was also followed and studied. This study offers new information related to the thermal behavior of ZHC, especially regarding the EPR data which is reported for the first time on this subject and material.

High performance FETs based on ZnO nanowires synthesized by low cost methods.

Single ZnO nanowires prepared by wet and dry methods are used as channels in high performance back-gated field effect transistors working in low power operation mode, with on-off ratios up to 105 and mobilities up to 167 cm2 V-1 s-1. The nanowires' properties, generated by the growth techniques, influence the parameters of the transistors, therefore a throughout comparison is made.

Composites of Titanium-Molybdenum Mixed Oxides and Non-Traditional Carbon Materials: Innovative Supports for Platinum Electrocatalysts for Polymer Electrolyte Membrane Fuel Cells.

TiO2-based mixed oxide-carbon composite support for Pt electrocatalysts provides higher stability and CO tolerance under the working conditions of polymer electrolyte membrane fuel cells compared to traditional carbon supports. Non-traditional carbon materials like graphene nanoplatelets and graphite oxide used as the carbonaceous component of the composite can contribute to its affordability and/or functionality. Ti(1-x)MoxO2-C composites involving these carbon materials were prepared through a sol-gel route; the effect of the extension of the procedure through a solvothermal treatment step was assessed. Both supports and supported Pt catalysts were characterized by physicochemical methods. Electrochemical behavior of the catalysts in terms of stability, activity, and CO tolerance was studied. Solvothermal treatment decreased the fracture of graphite oxide plates and enhanced the formation of a reduced graphene oxide-like structure, resulting in an electrically more conductive and more stable catalyst. In parallel, solvothermal treatment enhanced the growth of mixed oxide crystallites, decreasing the chance of formation of Pt-oxide-carbon triple junctions, resulting in somewhat less CO tolerance. The electrocatalyst containing graphene nanoplatelets, along with good stability, has the highest activity in oxygen reduction reaction compared to the other composite-supported catalysts.

Composite Photocatalysts with Fe, Co, and Ni Oxides on Supports with Tetracoordinated Ti Embedded into Aluminosilicate Gel during Zeolite Y Synthesis.

Ti-aluminosilicate gels were used as supports for the immobilization of Fe, Co, and Ni oxides (5%) by impregnation and synthesis of efficient photocatalysts for the degradation of ß-lactam antibiotics from water. Titanium oxide (1 and 2%) was incorporated into the zeolite network by modifying the gel during the zeolitization process. The formation of the zeolite Y structure and its microporous structure were evidenced by X-ray diffraction and N2 physisorption. The structure, composition, reduction, and optical properties were studied by X-ray diffraction, H2-TPR, XPS, Raman, photoluminescence, and UV-Vis spectroscopy. The obtained results indicated a zeolite Y structure for all photocatalysts with tetracoordinated Ti4+ sites. The second transitional metals supported by the post-synthesis method were obtained in various forms, such as oxides and/or in the metallic state. A red shift of the absorption edge was observed in the UV-Vis spectra of photocatalysts upon the addition of Fe, Co, or Ni species. The photocatalytic performances were evaluated for the degradation of cefuroxime in water under visible light irradiation. The best results were obtained for iron-immobilized photocatalysts. Scavenger experiments explained the photocatalytic results and their mechanisms. A different contribution of the active species to the photocatalytic reactions was evidenced.

Silver nanoparticles decorated ZnO-CuO core-shell nanowire arrays with low water adhesion and high antibacterial activity.

Nanostructured surfaces based on silver nanoparticles decorated ZnO-CuO core-shell nanowire arrays, which can assure protection against various environmental factors such as water and bacteria were developed by combining dry preparation techniques namely thermal oxidation in air, radio frequency (RF) magnetron sputtering and thermal vacuum evaporation. Thus, high-aspect-ratio ZnO nanowire arrays were grown directly on zinc foils by thermal oxidation in air. Further ZnO nanowires were coated with a CuO layer by RF magnetron sputtering, the obtained ZnO-CuO core-shell nanowires being decorated with Ag nanoparticles by thermal vacuum evaporation. The prepared samples were comprehensively assessed from morphological, compositional, structural, optical, surface chemistry, wetting and antibacterial activity point of view. The wettability studies show that native Zn foil and ZnO nanowire arrays grown on it are featured by a high water droplet adhesion while ZnO-CuO core-shell nanowire arrays (before and after decoration with Ag nanoparticles) reveal a low water droplet adhesion. The antibacterial tests carried on Escherichia coli (a Gram-negative bacterium) and Staphylococcus aureus (a Gram-positive bacterium) emphasize that the nanostructured surfaces based on nanowire arrays present excellent antibacterial activity against both type of bacteria. This study proves that functional surfaces obtained by relatively simple and highly reproducible preparation techniques that can be easily scaled to large area are very attractive in the field of water repellent coatings with enhanced antibacterial function.

Reductive Treatment of Pt Supported on Ti0.8Sn0.2O2-C Composite: A Route for Modulating the Sn-Pt Interactions.

The composites of transition metal-doped titania and carbon have emerged as promising supports for Pt electrocatalysts in PEM fuel cells. In these multifunctional supports, the oxide component stabilizes the Pt particles, while the dopant provides a co-catalytic function. Among other elements, Sn is a valuable additive. Stong metal-support interaction (SMSI), i.e., the migration of a partially reduced oxide species from the support to the surface of Pt during reductive treatment is a general feature of TiO2-supported Pt catalysts. In order to explore the influence of SMSI on the stability and performance of Pt/Ti0.8Sn0.2O2-C catalysts, the structural and catalytic properties of the as prepared samples measured using XRD, TEM, XPS and electrochemical investigations were compared to those obtained from catalysts reduced in hydrogen at elevated temperatures. According to the observations, the uniform oxide coverage of the carbon backbone facilitated the formation of Pt-oxide-C triple junctions at a high density. The electrocatalytic behavior of the as prepared catalysts was determined by the atomic closeness of Sn to Pt, while even a low temperature reductive treatment resulted in Sn-Pt alloying. The segregation of tin oxide on the surface of the alloy particles, a characteristic material transport process in Sn-Pt alloys after oxygen exposure, contributed to a better stability of the reduced catalysts.

Phytochemical Synthesis of Silver Nanoparticles and Their Antimicrobial Investigation on Cotton and Wool Textiles.

The use of bio-based reagents for silver nanoparticle (AgNP) production has gained much attention among researchers as it has paved the way for environmentally friendly approaches at low cost for synthesizing nanomaterials while maintaining their properties. In this study, Stellaria media aqueous extract was used for silver nanoparticle phyto-synthesis, and the resulting treatment was applied to textile fabrics to test its antimicrobial properties against bacteria and fungi strains. The chromatic effect was also established by determining the L*a*b* parameters. For optimizing the synthesis, different ratios of extract to silver precursor were tested using UV-Vis spectroscopy to observe the SPR-specific band. Moreover, the AgNP dispersions were tested for their antioxidant properties using chemiluminescence and TEAC methods, and the phenolic content was evaluated by the Folin-Ciocâlteu method. For the optimal ratio, values of average size, 50.11 ± 3.25 nm, zeta potential, -27.10 ± 2.16 mV, and polydispersity index, 0.209, were obtained via the DLS technique and zeta potential measurements. AgNPs were further characterized by EDX and XRD techniques to confirm their formation and by microscopic techniques to evaluate their morphology. TEM measurements revealed cvasi-spherical particles with sizes in the range of 10-30 nm, while SEM images confirmed their uniform distribution on the textile fiber surface.

Green synthesis of aminated hyaluronic acid-based silver nanoparticles on modified titanium dioxide surface: Influence of size and chemical composition on their biological properties.

This is the first report on an efficient, "environmentally friendly" chemical reduction method for the synthesis of aminated hyaluronic acid-based silver nanoparticles on the modified surface of titanium dioxide nanoparticles aimed for biological applications. Silver nanoparticles exhibit well-known physical-chemical and optical properties appropriate for different biological applications. Modifying the nanoparticles leads to a change in their expected bioactivity. This represents an important topic for the current research. We have developed a novel aminated hyaluronic acid (HA-EDA)-based protocol to obtain silver nanoparticles, in which HA-EDA was used for the first time as a reducing and stabilizing agent. The effect of the size of silver nanoparticles on the titanium dioxide surface and the chemical composition of the obtained materials were investigated by TEM, XRD, XPS, ATR-FTIR, Raman spectroscopy, NMR and H2-TPR analyses. The antioxidant, in vitro biocompatibility, and antimicrobial activity of the fabricated composites have been evaluated. The results prove that the prepared materials exhibit antimicrobial, antioxidant, and anti-inflammatory activity, thus providing protection against infection and supporting tissue regeneration, these two key effects being of paramount importance for promoting wound healing.

A Nanocomposite Sol-Gel Film Based on PbS Quantum Dots Embedded into an Amorphous Host Inorganic Matrix.

In this study, a sol-gel film based on lead sulfide (PbS) quantum dots incorporated into a host network was synthesized as a special nanostructured composite material with potential applications in temperature sensor systems. This work dealt with the optical, structural, and morphological properties of a representative PbS quantum dot (QD)-containing thin film belonging to the Al2O3-SiO2-P2O5 system. The film was prepared using the sol-gel method combined with the spin coating technique, starting from a precursor solution containing a suspension of PbS QDs in toluene with a narrow size distribution and coated on a glass substrate in a multilayer process, followed by annealing of each deposited layer. The size (approximately 10 nm) of the lead sulfide nanocrystallites was validated by XRD and by the quantum confinement effect based on the band gap value and by TEM results. The photoluminescence peak of 1505 nm was very close to that of the precursor PbS QD solution, which demonstrated that the synthesis route of the film preserved the optical emission characteristic of the PbS QDs. The photoluminescence of the lead sulfide QD-containing film in the near infrared domain demonstrates that this material is a promising candidate for future sensing applications in temperature monitoring.

Mesoporous Composite Bioactive Compound Delivery System for Wound-Healing Processes.

Currently, the treatment of wounds is still a challenge for healthcare professionals due to high complication incidences and social impacts, and the development of biocompatible and efficient medicines remains a goal. In this regard, mesoporous materials loaded with bioactive compounds from natural extracts have a high potential for wound treatment due to their nontoxicity, high loading capacity and slow drug release. MCM-41-type mesoporous material was synthesized by using sodium trisilicate as a silica source at room temperature and normal pressure. The synthesized mesoporous silica was characterized by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), N2 absorption-desorption (BET), Dynamic Light Scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR), revealing a high surface area (BET, 1244 m2/g); pore diameter of approx. 2 nm; and a homogenous, ordered and hexagonal geometry (TEM images). Qualitative monitoring of the desorption degree of the Salvia officinalis (SO) extract, rich in ursolic acid and oleanolic acid, and Calendula officinalis (CO) extract, rich in polyphenols and flavones, was performed via the continuous recording of the UV-VIS spectra at predetermined intervals. The active ingredients in the new composite MCM-41/sage and marigold (MCM-41/SO&CO) were quantified by using HPLC-DAD and LC-MS-MS techniques. The evaluation of the biological composites' activity on the wound site was performed on two cell lines, HS27 and HaCaT, naturally involved in tissue-regeneration processes. The experimental results revealed the ability to stimulate collagen biosynthesis, the enzymatic activity of the main metalloproteinases (MMP-2 and MMP-9) involved in tissue remodeling processes and the migration rate in the wound site, thus providing insights into the re-epithelializing properties of mesoporous composites.

A new method for obtaining the magnetic shape anisotropy directly from electron tomography images.

A new methodology to obtain magnetic information on magnetic nanoparticle (MNP) systems via electron tomography techniques is reported in this work. The new methodology is implemented in an under-development software package called Magn3t, written in Python and C++. A novel image-filtering technique that reduces the highly undesired diffraction effects in the tomography tilt-series has been also developed in order to increase the reliability of the correlations between morphology and magnetism. Using the Magn3t software, the magnetic shape anisotropy magnitude and direction of magnetite nanoparticles has been extracted for the first time directly from transmission electron tomography.

Self-connected CuO-ZnO radial core-shell heterojunction nanowire arrays grown on interdigitated electrodes for visible-light photodetectors.

An original photodetector system based on self-connected CuO-ZnO radial core-shell heterojunction nanowire arrays grown on metallic interdigitated electrodes, operating as visible-light photodetector was developed by combining simple preparation approaches. Metallic interdigitated electrodes were fabricated on Si/SiO2 substrates using a conventional photolithography process. Subsequently, a Cu layer was electrodeposited on top of the metallic interdigitated electrodes. The CuO nanowire arrays (core) were obtained by thermal oxidation in air of the Cu layer. Afterwards, a ZnO thin film (shell) was deposited by RF magnetron sputtering covering the surface of the CuO nanowires. The morphological, structural, compositional, optical, electrical and photoelectrical properties of the CuO nanowire arrays and CuO-ZnO core-shell nanowire arrays grown on metallic interdigitated electrodes were investigated. The performances of the devices were evaluated by assessing the figures of merit of the photodetectors based on self-connected CuO-ZnO core-shell heterojunction nanowire arrays grown on the metallic interdigitated electrodes. The radial p-n heterojunction formed between CuO and ZnO generates a type II band alignment that favors an efficient charge separation of photogenerated electron-hole pairs at the CuO-ZnO interface, suppressing their recombination and consequently enhancing the photoresponse and the photoresponsivity of the photodetectors. The electrical connections in the fabricated photodetector devices are made without any additional complex and time-consuming lithographic step through a self-connecting approach for CuO-ZnO core-shell heterojunction nanowire arrays grown directly onto the Ti/Pt metallic interdigitated electrodes. Therefore, the present study provides an accessible path for employing low dimensional complex structures in functional optoelectronic devices such as photodetectors.

Relationship between the Formation of Magnetic Clusters and Hexagonal Phase of Gold Matrix in AuxFe1-x Nanophase Thin Films.

AuxFe1-x nanophase thin films of different compositions and thicknesses were prepared by co-deposition magnetron sputtering. Complex morpho-structural and magnetic investigations of the films were performed by X-ray Diffraction, cross-section Transmission Electron Microscopy, Selected Area Electron Diffraction, Magneto Optical Kerr Effect, Superconducting Quantum Interference Device magnetometry and Conversion Electron Mössbauer Spectroscopy. It was proven that depending on the preparation conditions, different configurations of defect α-Fe magnetic clusters, i.e., randomly distributed or auto-assembled in lamellar or filiform configurations, can be formed in the Au matrix. A close relationship between the Fe clustering process and the type of the crystalline structure of the Au matrix was underlined, with the stabilization of a hexagonal phase at a composition close to 70 at. % of Au and at optimal thickness. Due to different types of inter-cluster magnetic interactions and spin anisotropies, different types of magnetic order from 2D Ising type to 3D Heisenberg type, as well as superparamagnetic behavior of non-interacting Fe clusters of similar average size, were evidenced.

Electrocatalytic Properties of Mixed-Oxide-Containing Composite-Supported Platinum for Polymer Electrolyte Membrane (PEM) Fuel Cells.

TiO2-based mixed oxide-carbon composite supports have been suggested to provide enhanced stability for platinum (Pt) electrocatalysts in polymer electrolyte membrane (PEM) fuel cells. The addition of molybdenum (Mo) to the mixed oxide is known to increase the CO tolerance of the electrocatalyst. In this work Pt catalysts, supported on Ti1-xMoxO2-C composites with a 25/75 oxide/carbon mass ratio and prepared from different carbon materials (C: Vulcan XC-72, unmodified and functionalized Black Pearls 2000), were compared in the hydrogen oxidation reaction (HOR) and in the oxygen reduction reaction (ORR) with a commercial Pt/C reference catalyst in order to assess the influence of the support on the electrocatalytic behavior. Our aim was to perform electrochemical studies in preparation for fuel cell tests. The ORR kinetic parameters from the Koutecky-Levich plot suggested a four-electron transfer per oxygen molecule, resulting in H2O. The similarity between the Tafel slopes suggested the same reaction mechanism for electrocatalysts supported by these composites. The HOR activity of the composite-supported electrocatalysts was independent of the type of carbonaceous material. A noticeable difference in the stability of the catalysts appeared only after 5000 polarization cycles; the Black Pearl-containing sample showed the highest stability.

Synthesis and Characterization of Hematite-Based Nanocomposites as Promising Catalysts for Indigo Carmine Oxidation.

The hematite-based nanomaterials are involved in several catalytic organic and inorganic processes, including water decontamination from organic pollutants. In order to develop such species, a series of bimetallic hematite-based nanocomposites were obtained by some goethite composites-controlled calcination. Their composition consists of various phases such as α-FeOOH, α-Fe2O3 or γ-Fe2O3 combined with amorphous (Mn2O3, Co3O4, NiO, ZnO) or crystalline (CuO) oxides of the second transition ion from the structure. The component dimensions, either in the 10-30 or in the 100-200 nm range, together with the quasi-spherical or nanorod-like shapes, were provided by Mössbauer spectroscopy and powder X-ray diffraction as well as transmission electron microscopy data. The textural characterization showed a decrease in the specific area of the hematite-based nanocomposites compared with corresponding goethites, with the pore volume ranging between 0.219 and 0.278 cm3g-1. The best catalytic activity concerning indigo carmine removal from water in hydrogen peroxide presence was exhibited by a copper-containing hematite-based nanocomposite sample that reached a dye removal extent of over 99%, which correlates with both the base/acid site ratio and pore size. Moreover, Cu-hbnc preserves its catalytic activity even after four recyclings, when it still reached a dye removal extent higher than 90%.