National Institute Of Materials Physics - Romania

Herein we present a comparative study among different spray-coated nanometric mesoporous electron transporting layers (ETLs) in perovskite solar cells (PSC), namely m-TiO2, 2 , m-SnO2 2 and m-SnO2 2 quantum dots (mSnO2QDs). 2 QDs). The solutions used for deposition were prepared from commercial pastes and colloidal suspensions for m-TiO2 2 and m-SnO2. 2 . For m-SnO2QDs 2 QDs in-house QDs solutions were prepared. The formamidiniummethylamonium-potassium (FAMA@10 K) has been used as light absorber material in the fabricated PSCs. The structural, compositional and morphological studies, correlated with the photovoltaic performance of PSCs, indicate that the m-SnO2 2 QDs layer is the best candidate among the three investigated mesoporous ETLs. Compared with the suspensions used for the other two ETLs, the in-house prepared SnO2 2 QDs solution presents smaller agglomerates of nanoparticles and results in the formation of a thinner, more uniform and compact mesoporous ETL. The FAMA@10 K perovskite deposited on m-SnO2 2 QDs ETL presents a lower roughness, better uniformity and a higher amount of PbI2. 2 . Our work unveils that the SnO2 2 QDs solution can be easily produced in laboratory and when is deposited as mesoporous scaffold in a PSC with FAMA@10 K perovskite, the power conversion efficiency increases up to 14.90 %, being with up to 27 % larger than in the PSCs with m-TiO2 2 and mSnO2 2 ETLs prepared from commercial solutions. By modeling the J-V dynamic hysteresis with more than 90 % match between the calculated and experimental J-V data, for all three types of mesoporous ETLs, the relevant parameters that explain the hysteresis magnitude and account for ionic-induced recombination processes in PSCs were determined.

Laser thin layer deposition technologies were applied to develop organic heterostructures on flexible transparent conductive electrode (TCE). Flexible substrates such as flexible glass (FG), polyethersulfone (PES), amorphous polyethylene terephthalate (PET-A) and biaxially-oriented polyethylene terephthalate (PET-B) were employed to assess the influence of the substrate type on the optical and electrical characteristics of the organic devices. For comparison reason, the organic heterostructures were fabricated on rigid glass substrate and commercially available indium tin oxide (ITO)-coated PET. Hence, flexible and rigid glass substrates were coated with ITO film by pulsed laser deposition (PLD) at low fluence, subsequently a blend layer based on zinc phthalocyanine (ZnPc) and N, N '-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14) being deposited by matrix assisted pulsed laser evaporation (MAPLE) on the TCE film. The investigations evidenced that the roughness and the substrate type can strongly influence the properties of the ITO layer deposited by PLD as well as the optical and electrical characteristics of the organic heterostructures based on the blend layer deposited by MAPLE. Thus, the lowest roughness (0.8 nm) and the best Hall mobility (41.9 cm2/V center dot s) were achieved for ITO coatings deposited on flexible glass substrate. Also, the highest current density value (9.3 x 10- 4 A/cm2 at 0.5 V) was reached for the organic heterostructures fabricated on this type of flexible substrate.

Hydroxyapatite (HAp), resembling human bone tissue, is a promising biomaterial for dental and hip prosthetics. Incorporating fluorine ions enhances HAp properties, particularly in dental restoration. This new study examines the physicochemical and biological properties of fluorine substituted hydroxyapatite (FHAp) coatings. Structural and morphological properties of the coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental composition of the FHAp coatings was studied using energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy. Fourier Transform Infrared spectroscopy (FTIR) investigations were also conducted. The typical peaks identified in XRD patterns of the FHAp were associated with pure hydroxyapatite with hexagonal structure. The general XPS spectrum of FHAp coatings shows peaks corresponding to the constituent elements of stoichiometric HAp as well as the presence of F that was used as a substituent. Consequently, the FTIR studies results underlined the presence of hydroxyapatite in the FHAp coatings. The SEM images reveal the presence of a uniform and continuous layer of particle conglomerates evenly distributed across the FHAp surface. Valuable information about the FHAp coating's wettability, adhesion and coating thickness were also obtained. Also, the AFM images suggest the absence of the significant irregularities from the surface of the FHAp coatings. Investigations of FHAp coatings reveal promising outcomes for cell viability and proliferation. Detailed analysis of FHAp's 3D surface characteristics and roughness, following ISO 25178-2:2012 standards, highlights their favorable biocompatibility, supporting MG63 cell proliferation. The surface roughness parameters of FHAp coatings were found to vary, with Sa values spanning from 0.029 +/- 0.004 mu m to 0.778 +/- 0.007 mu m, while Sq ranged from 0.035 +/- 0.005 mu m to 0.907 +/- 0.011 mu m. Furthermore, FHAp exhibits skewness (Ssk) from -0.048 +/- 0.006 to 0.195 +/- 0.009, kurtosis (Sku) from -0.600 +/- 0.011 to -1.050 +/- 0.021, and fractal dimension from 2.14 +/- 0.01 to 2.19 +/- 0.01, indicating consistent surface complexity and favorable properties. The Minkowski Functionals mirror the morphological observations from AFM images, emphasizing their dynamic influence on the samples' surfaces.

In this work, three methods for the synthesis of composites based on poly(ortho-toluidine) (POT) and WS2 are reported: (a) the solid-state interaction (SSI) of POT with WS2 nanoparticles (NPs); (b) the in situ chemical polymerization (ICP) of ortho-toluidine (OT); and (c) the electrochemical polymerization (ECP) of OT. The preparation of WS2 sheets was performed by the ball milling of the WS2 NPs followed by ultrasonication in the solvent N,N'-dimethyl formamide. During the synthesis of the POT/WS2 composites by SSI and ICP, an additional exfoliation of the WS2 NPs was reported. In this work, we demonstrated the following: (a) the ICP method leads to POT/WS2 composites, which contain repeating units of POT in the leucoemeraldine salt (LS) state, while (b) the ECP method leads to POT/WS2 composites, which contain repeating units of POT in the emeraldine salt (ES) state. Capacitances equal to 123.5, 465.76, and 751.6 mF cm-2 in the cases of POT-ES/WS2 composites, synthesized by SSI, ICP, and ECP, respectively, were reported.

This study examined the gradual replacement of Ca2+ with a small amount of Mg2+ ions (0-1 wt%) in selected calcium phosphates commonly used in regenerative medicine: hydroxyapatite Ca10(PO4)6(OH)2, brushite CaHPO4 center dot 2H2O, and (3-tricalcium phosphate ((3TCP) Ca3(PO4)2. These compounds were obtained using precipitation reactions from aqueous solutions, followed by appropriate thermal treatment (drying or furnace heating). The microstructure and physicochemical properties of the materials were thoroughly analysed using powder X-ray diffraction (PXRD), scanning and transmission electron microscopy (SEM and TEM), and mid-infrared spectroscopy (FT-IR). Additionally, the release of Mg2+ ions from the selected materials was investigated, and a preliminary in vitro toxicity assessment was performed. The results showed that the introduction of magnesium ions up to 1 wt% was achieved with relatively high efficiency (63-82 % for brushite, 77-97 % for hydroxyapatite, and 88-100 % for (3-tricalcium phosphate). The entire series of hydroxyapatites was phase-homogeneous, but monetite was observed as an additional phase in the case of brushite samples. In contrast, several (3TCP samples were contaminated with a small amount of calcium oxide and hydroxide. The incorporation of Mg2+ ions significantly impacted the unit cell parameters of each type of calcium phosphate and the ultrastructure of the obtained powders. With an increase in the amount of introduced magnesium, the resulting crystals became smaller and showed a greater tendency to form aggregates. The obtained results indicate that it is possible to obtain calcium phosphate materials containing Mg2+ ions with a gradual release of ions. The fastest ions release occurred from the brushite sample, while the slowest was from the apatitic powder, which is in great accordance with the solubility of the materials. All samples, except for Mg0.5-Bru, were non-cytotoxic.

The purpose of this work is to obtain different kinds of advanced nanostructures with four materials of interest: carbon, titanium, aluminum and silicon, deposited by Thermionic Vacuum Arc (TVA) technology on the Si substrate, in two cases: C/Ti/C/Al/C/Si multilayer film and C+Ti/C+Al/C+Si composite film with inclusion of nitrogen. Also, for each type of samples some parameters varied: substrates temperature (Room Temperature, 200 degrees C, 300 degrees C, 400 degrees C) and the bias voltage applied on the substrates, i.e. - 400 V. Thermal Desorption Spectroscopy (TDS) analyses revealed the presence of nitrogen in all cases. The Raman spectra reveal that the film nitrogen treatments leads to the formation of nitrides for each compound. The infrared absorption spectra are dominated by the formation of C-N bonds, which are the same as in the Raman spectra. EDX and Elemental composition show the values of atomic percentage depending on the substrate deposition temperature. TEM and XPS depth profiles are studied. Based on nanoindentation studies, the Young modulus and hardness are measured. The tribology measurements are also performed.

The present study aims to develop and investigate the biological response of a bone substitute based on electrospun polyvinylidene fluoride (PVDF) fibres, which are either embedded or coated with a silicate bioglass belonging to SiO2-P2O5-CaO-Na2O oxide system. This bioglass is substituted with antibacterial agents, silver (Ag) and cerium (Ce), while deposition methods utilized include pulsed laser deposition (PLD) and matrixassisted pulsed laser evaporation (MAPLE). The results showed the inhomogeneous distribution of the glassy particulate phase in the polymer fibres when using electrospinning as single processing technique. In contrast, the materials achieved by combining the electrospinning with laser ablation displayed a continuous coating of glass at the polymer fibres surface. The thickness and roughness of this layer can be easily tuned as a function of deposition conditions, as it was demonstrated when changing the dispersion medium or working pressure. Good results were obtained for all coated PVDF fibres, but especially in the case of PLD processing with a thicker layer of silicate glass, the imaging evaluation suggested a superior beneficial impact on cellular metabolism. Such scaffolds, with controlled porosity, engineered surface and potential piezoelectric properties represent important candidates for the field of personalized bone substitutes.

Capitalizing on invasive plant species and stopping their aggressive spread might be achieved by using them as a renewable source of useful products such as cellulose. The study aimed to develop new cellulose-based food packaging materials with antioxidant and antimicrobial activity. The cellulose was extracted from the invasive plant species Robinia pseudoacacia pods, crosslinked with citric acid, used as reinforcement for polyvinyl alcohol (PVA) and functionalized with ferulic acid (FA). The obtained materials were characterized by XRD, ATR-FTIR, contact angle and SEM. The materials exhibited low solubility in water and the swelling degree was proportional to the FA content. The FA release from the matrix was assessed by HPLC and the antioxidant profile by CUPRAC, FRAP, and TEAC methods. The obtained materials inhibited the growth of bacteria, yeasts and molds, being especially active on Gram-positive bacteria and yeasts. Overall, the most promising formulation for further developing new packaging materials for products with water activity less than 0.95 was the one with the highest FA content.

Kynurenic acid (KA) is an active metabolite of tryptophan with notable biological effects, such as antioxidant, neuroprotective, and anti-inflammatory properties. It often undergoes changes of the concentration in biological fluids in chronic diseases. Thus, detecting KA is of great importance for diagnosing inflammatory and neurodegenerative conditions, monitoring disease progression, and assessing responses to pharmacological treatment. This study aimed to design a tailored, flexible platform for sensitive and direct electrochemical detection of KA in biological fluids. Carbon-based electrodes were custom-printed in the lab using specialized inks and flexible substrates. The working electrodes were further functionalized with graphene oxide and subsequently electrochemically reduced to increase the sensitivity toward the analyte. An optimized differential pulse voltammetry protocol was developed for KA detection. The elaborated platform was firstly characterized and then evaluated regarding the analytical performances. It showed a good limit of detection (3 nM and demonstrated the capability to detect KA across a broad concentration range (0.01-500 mu M). Finally, the elaborated flexible platform, was succesfully applied for KA determination in serum and saliva samples, in comparison with an optimized HPLC-UV method. The developed platform is the first example of in-lab printed flexible platform reported in literature so far for KA detection. It is also the first study reported in the literature of detection of KA in raw saliva collected from 10 subjects. The sensitivity towards the target analyte, coupled with the adaptability and portability, showcases the potential of this platform for thus illustrating great potential for further development of wearable sensors and biomedical applications.

Cu-doped hydroxyapatite (CuHAp) thin films were obtained using spin coating method. To make these thin films, CuHAp suspensions obtained by sol-gel method were used. The coatings obtained were thermally treated at 500 degrees C. After the thermal treatment, the thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Moreover, the stability of the suspensions before being used to obtain the thin films was certified by dynamic light scattering (DLS), zeta potential methods and ultrasound measurements. In the XRD patterns, the peaks associated with hexagonal hydroxyapatite were identified in accordance with JCPDS no. 09-0432. EDS and XPS results confirmed the presence of Cu ions in the samples. Data about the morphological features and chemical composition of CuHAp thin films were obtained by performing scanning electron microscopy (SEM) measurements. Our results suggest that the CuHAp thin films surface is continuous and homogenous. The presence of the functional groups in the CuHAp thin films was confirmed by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy studies. Information about the surface topography of the CuHAp thin films has been obtained using atomic force microscopy (AFM). The AFM images determined that the surface topography of the CuHAp thin layer is homogenous and continuous without presenting any unevenness or fissures. The cytotoxicity of CuHAp thin films was assessed using human gingival fibroblasts (HGF-1) cells. The results of the cell viability assays demonstrated that the thin films presented good biocompatible properties towards the HGF-1 cells. Additionally, the adherence and development of HGF-1 cells on the surface of CuHAp thin films were determined using AFM. The AFM surface topographies highlighted that the CuHAp thin film's surface favored the attachment and proliferation of HGF-1 cells on their surface.