National Institute Of Materials Physics - Romania

Gain-layer degradation from exposure to radiation limits the use of Low-Gain Avalanche Diodes (LGADs) in high energy particle physics detector experiments. Proper understanding of how the gain-layer is altered is not available on a defect level. Only measurements for materials with much lower effective doping concentrations are available. The direct study of the gain-layer is not possible with typical defect spectroscopy measurements like Thermally Stimulated Currents (TSC) and Deep-Level Transient Spectroscopy (DLTS). To combat this problem and gain a better understanding of the processes which degrade LGADs, the Gain-Layer Project was started. Within this project 19050 diodes were produced with various Boron, Phosphorus, Oxygen and Carbon concentrations. The material used is low-resistivity p-type Silicon. The effective doping concentrations are in the order of typical LGAD gain-layers. These diodes will serve the defect community in the coming years for various studies. This article introduces this project with detailed descriptions of the diodes, their flavours and their processing, and reports on results from I-V, C-V, SIMS and DLTS measurements on unirradiated diodes.

Graphene oxide (GO) provides a versatile platform for the development of antimicrobial and anti-adhesive materials, particularly when combined with covalently immobilized bioactive compounds but translating antibiotic activity into a stable layer without clinically relevant drug leaching remains challenging. Here, we report a covalently engineered GO-moxifloxacin (GO-MOX) composite obtained by grafting MOX onto ethylenediaminefunctionalized GO via carbodiimide coupling. The successful functionalization was supported by complementary physicochemical analyses, including FTIR, NMR, Raman, XPS, TGA, SEM/EDS and XRD. TGA indicated a high MOX loading of approximately 44.75 wt%, while HPLC analysis revealed that extractable/free MOX represented only 0.0586% of the total MOX content, supporting the predominantly covalent and minimally releasing character of the material. GO-MOX showed pronounced antimicrobial activity against representative ESKAPEE pathogens, with MIC values of 7.81 & micro;g/mL against E. coli and 62.5 & micro;g/mL against the tested Gram-positive strains. In the antimycobacterial assay, GO-MOX markedly inhibited the growth of both drug-susceptible and rifampicin/isoniazid-resistant Mycobacterium tuberculosis strains under the tested conditions. Anti-adherence activity was observed at sub-inhibitory concentrations, with MBEC values of 1.95 & micro;g/mL for E. coli and 7.81 & micro;g/mL for S. aureus, suggesting interference with early bacterial attachment. Additional analyses on mature biofilms formed on titanium substrates showed that GO-based treatments, particularly GO-MOX, affected biofilm viability, promoted membrane permeabilization, and altered extracellular matrix components, including extra-cellular proteins, nucleic acids/eDNA-like fractions and polysaccharides. In vitro cellular assays showed that normal MRC-5 fibroblasts recovered metabolic activity to >= 80% after 72 h, whereas A549 cells displayed a concentration-and time-dependent decrease in viability. ROS generation and Caspase-3 activity further suggested that the selective antiproliferative response observed in A549 cells may be associated, at least in part, with oxidative stress-mediated apoptotic mechanisms. In silico target prediction and structural inspection of MOX-topoisomerase complexes suggested that GO-MOX may retain a MOX-related contribution involving bacterial DNA gyrase/topoisomerase IV, while GO may provide additional contact-associated interfacial effects. Overall, GO-MOX emerges as a promising antimicrobial and anti-adhesive nanoplatform with cell-selective antiproliferative effects, supporting its further investigation for the future development of biomedical antimicrobial surfaces and coatings.

This work presents a comprehensive investigation of the structural, microstructural, magnetic, and magneto-caloric properties of La0.9-xPbxNa0.1MnO3 (x = 0 and 0.1), synthesized through a flash combustion technique and subsequently pressed into pellets. Structural analysis confirms that both samples crystallize in a rhombohedral structure without detectable secondary phases or impurities. Microstructural observations reveal a homogeneous morphology in both compositions, with a noticeable grain growth effect induced by Pb doping. Magnetic measurements show a clear paramagnetic-ferromagnetic phase transition in both samples. The Curie temperature shifts from 179 K for the undoped compound to 309 K for the Pb-doped compounds. Furthermore, the magnetic entropy change and the relative cooling power increase from 3.01 J/kg.K and 184.72 J/kg for La0.9Na0.1MnO3 to 4.56 J/kg.K and 291.29 J/kg for La0.8Pb0.1Na0.1MnO3. Together, these results highlight the beneficial effect of Pb doping in the studied system for room-temperature magnetic refrigeration applications.

Multilayer oxide/metal/oxide (OMO) structures emerge as suitable alternative to indium tin oxide (ITO) in transparent conductive electrode (TCE) field mainly due to their high visible light transmittance and low resistivity. Moreover, OMO structures are appropriate for flexible organic optoelectronic devices being less susceptible to cracking than single-layer ITO electrodes. Therefore, the present study is focused on the assessment of the properties of ZnO/Ag/ZnO (ZAZ) structures deposited by consecutive radio frequency magnetron sputtering (ZnO) and thermal vacuum evaporation (Ag) on flexible substrates such as polyethylene terephthalate, polyethersulfone and flexible glass. Additionally, the ZAZ deposition was carried out on patterned polyethersulfone in order to evaluate the nanopatterning effect on the properties of the multilayer structures. For comparison, ZAZ structures were also deposited on rigid glass substrate, this being commonly used in optoelectronic devices. The optical and electrical measurements reveal that the roughness of the deposition substrate has a significant impact on the transmittance and sheet resistance of the ZAZ multilayers. Thus, the best performance in terms of transmittance at 550 nm wavelength (82.7%), sheet resistance (9.5 52/square) and figure of merit (15.75x10-3 52-1), correlated with the lowest roughness (2.3 nm), is achieved for the structure fabricated on flexible glass. The values of the TCE key parameters endorse the developed ZAZ structures for optoelectronic applications.

This study explores the impact of incorporating a small quantity of conductive boron-doped diamond powder (BDDP) into cobalt oxide-based electrocatalysts prepared via solution combustion, aiming to improve their performance in both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Structural analyses using X-ray diffraction and Raman spectroscopy identify Co3O4 as the primary phase, unaffected by the presence of BDDP. In contrast, X-ray photoelectron spectroscopy reveals that adding BDDP promotes the formation of additional CoO species and enhances surface levels of Co(OH)2, oxygen vacancies, adsorbed hydroxyl groups, and water, features that are beneficial for oxygen electrocatalysis. Electrochemical testing demonstrates that the Co3O4-BDDP catalyst delivers markedly enhanced OER activity, including a decrease in Tafel slope of about 15% at lower applied potentials and up to 30% at higher ones, along with almost a doubling of the turnover frequency. For ORR, the inclusion of BDDP leads to nearly a fourfold rise in reduction current at-0.36 V. Furthermore, the comparable Tafel slopes for OER and ORR suggest efficient kinetics in both directions, underscoring the promise of Co3O4-BDDP catalysts for applications in rechargeable metal-air batteries and unitized regenerative fuel cells.

This paper reports about bulk heterojunctions layers containing azomethine oligomers based on carbazole (AzC) or triphenylamine (AzPA) donor and alkyl perylene diimide derivative (PTCDI-12C) acceptor blended in different weight ratios (1:2), (1:3) and (1:4), prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) on flexible substrate of polyethylene terephthalate (PET) covered by ITO. The effect of the type of azomethine donor substituent group and mixed layer composition on the optical and electrical properties was investigated in correlation with the molecular aggregation particularities and surface topographical particularities of the layers.The strong absorption band between 400 and 650 nm was favored by the strong polarization interactions in the layers deposited by MAPLE from chloroform and the red shift of the UV-Vis absorption peaks of PTCDI-12C in the both types of bulk heterojunction layer confirmed the generation during the deposition mostly of J-aggregates, which are associated with the fluorescence emission.The correlation between the roughness, statistical analysis parameters obtained by height-to-height correlation function, grains shape and electrical behavior was analyzed. The samples prepared with AzC donor showed photoelectric behavior with the best parameters for AzC:PTCDI-12C in a weight ratio of (1:3), while the sample with AzPA:PTCDI-12C mixed layer showed an injection contact behavior with the best current (10(-4) A for voltage < 0.5 V) at a weight ratio of (1:2). Thus, the behavior of the heterostructures is affected by the type of azomethine: carbazole-azomethine can be potential candidates for optoelectronic applications while triphenylamine-azomethine for electronic application.[GRAPHICS].

Copper-doped hydroxyapatite (5CuHAp) coatings were obtained using the dip-coating technique and comprehensively characterized for structural, surface, and biological performance. X-ray diffraction confirmed phasepure hydroxyapatite with minimal Cu-induced lattice distortion. XPS revealed Cu2+ incorporation at 4.8 at. % and surface (Ca + Cu)/P ratio of 1.67. SEM and multiscale AFM showed homogeneous, crack-free coatings with hierarchical nanoscale features; maximum furrow depths ranged 0.022-0.65 mu m across MG63 incubation times, with fractal dimensions 2.44-2.57 and high directional anisotropy. Slope and frequency analyses indicated dominant surface orientations and multiscale periodicity (lambda = 7.1 mu m; phase 86-150 degrees). In vitro MG63 assays demonstrated rapid adhesion, spreading, and proliferation, correlating with nanoscale guidance cues and surface energy landscape. These findings establish adapted sol-gel 5CuHAp coatings as structurally coherent, bioactive, and osteoconductive substrates, offering precise nanoscale topography and compositional control for orthopedic and dental implant applications. The in vitro biocompatibility of the 5CuHAp coatings was evaluated using MG63 human osteosarcoma cells through complementary MTT and LDH assays. The MTT studies revealed high cell viability after 24, 48, and 72 h of exposure, indicating good cytocompatibility and the absence of significant inhibitory effects on the cell viability or proliferation. Furthermore, the LDH assay revealed low levels of enzyme release into the culture medium relative to control cells, suggesting minimal membrane damage and limited cytotoxic effects. Together, these results highlight that the 5CuHAp coatings exhibit favorable biological behavior and support their potential suitability for biomedical applications.

Composites based on TiO2 and single-walled carbon nanotubes (SWCNTs), highly separated in semiconducting tubes (S-SWCNTs) and as a mixture of metallic and semiconducting tubes (M + S-SWCNTs), were obtained by the interaction in the solid state. This interaction induces a change in the size of TiO2 particles from 23.67 nm to 28.2 and 150 nm, respectively, accompanied by an increase in the disorder state of the graphitic lattice of SWCNTs. We demonstrate by UV-VIS spectroscopy that the best performance in terms of rhodamine 6G (Rh6G) photodegradation is obtained in the case of the TiO2/S-SWCNT composite. The highest values of the Rh6G photodegradation efficiency were equal to 92% for an S-SWCNT concentration in the photocatalyst mass of 10 wt% and 94% for a 0.1 mM Rh6G solution with a pH equal to 1. We demonstrate that an important role is played by the O2(center dot)- and (OH)-O-center dot species in the photodegradation mechanism of Rh6G. This study contributes to a better understanding of the role of metallic and semiconducting carbon nanotubes in the photocatalysis field, highlighting that composites based on semiconducting SWCNTs and semiconducting metallic oxides are those that contribute essentially to the removal of dyes by exposure to the light emitted by a halogen lamp.

Using solid-state interactions, composites based on molybdenum disulfide (MoS2), poly(ortho-toluidine) (POT), and reduced graphene oxide (RGO) were prepared. Raman scattering and FTIR spectroscopic studies have demonstrated that the interaction of the RGO and MoS2 sheets with the POT-emeraldine base state (EB) leads to composites composed of RGO sheets non-covalently functionalized with pseudo-protonic POT doped with MoS2 and RGO covalently functionalized with POT-leucoemeraldine salt (LS). An alternative way to prepare these composites is the solid-state interaction of the RGO and MoS2 sheets with the POT-emeraldine salt (ES), resulting in composites composed of RGO non-covalently functionalized with POT-salt having pseudo-protonic acidic entities doped with MoS2 and RGO covalently functionalized with POT-leucoemeraldine base (LB). Using UV-Vis spectroscopy, we demonstrate that the exposure of these composites to UV light in protic polar solvents leads to the generation of partially de-doped POT-LB and POT-ES. The features of the composites after light exposure, as well as their transformation to the salt state, are highlighted by surface-enhanced Raman scattering. This study contributes to better understanding of the properties of the composites based on MoS2, POT, and RGO, highlighting the need to avoid the exposure of composites dissolved in polar protic solvents to UV light.

In this manuscript we report the development of magnesium doped hydroxyapatite in chitosan matrix (5HMC_0, Ca10 -xMgx(PO4)(6)(OH)(2), with x(Mg) = 0.05) by adapted sol-gel method. Then, the 5HMC_0 composite layers were developed using dip-coating technique. The obtained composite layers were exposed to Dulbecco's Modified Eagle Medium (DMEM) for 7 and 14 days. Then, the 5HMC samples were thoroughly analyzed both before and after immersion in DMEM for 7 and 14 days in order to investigate the structural and compositional changes induced by the DMEM environment. To perform a comprehensive evaluation, multiple characterization techniques were used, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). To investigate the chemical composition, bonding states, and surface characteristics of the 5HMC_0, 5HMC_7, and 5HMC_14 samples, X-ray photoelectron spectroscopy (XPS) analyses were performed. XPS provides detailed insight into the chemical transformations occurring at the composite surface. These methods provided detailed information on the surface morphology and chemical composition, of the 5HMC samples (before and after immersion in DMEM). FTIR analysis of 5HMC confirmed the presence of characteristic phosphate and amide bands at similar to 1043 cm(-)& sup1; and similar to 1650 cm(-)& sup1; , while AFM measurements revealed a surface roughness (Ra) of approximately 68.46 nm (for the 5HMC sample); SEM studies indicated a homogeneous, crack-free morphology (for the 5HMC sample), and XPS and EDS analysis showed the Mg incorporation in the 5HMC composite layers. The biological properties of 5HMC layers were evaluated before and after immersion in DMEM medium with the aid of HGF-1 cell line (ATCC CRL-2014). The cell viability assay MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) showed that the 5HMC layers supported the proliferation of the fibroblast cells on their surface (having a cell viability above 94%). More than that, this preliminary study highlights the importance of 5HMC layers, demonstrating their favorable physicochemical and biological characteristics after exposure to DMEM, supporting their potential suitability for applications in bone implants, as well as in the orthopedic and dental fields.