Dr. Daniel CRISAN
Scientific Researcher III
Laboratory of Functional Nanostructures
daniel[DOT]crisan[AT]infim[DOT]roPublications
1. Palladium-Coated Submicron Electrospun Polymeric Fibers with Immobilized Uricase for Uric Acid Determination in Body Fluids
Authors:
Leote, RJB; Crisan, DN; Matei, E; Enculescu, I; Diculescu, VC
Published: 2024 FEB 12 2024, ACS APPLIED POLYMER MATERIALS, 6, DOI: 10.1021/acsapm.3c02811
This work describes the development of a flexible uric acid (UA) biosensor based on palladium-coated submicrometer electrospun poly(methylmethacrylate) (PMMA) fibers metalized with gold and attached to polyethylene terephthalate substrate (Pd/Au/PMMA/PET). The morphological characterization conducted by scanning electron microscopy revealed nanoscale Pd dendritic structures. Electrochemical investigations in the absence and in the presence of redox probes demonstrated that these Pd nanostructures are responsible for a six-fold increase in the electroactive area and enhanced electron transfer kinetics when compared to the gold-coated electrospun fibers. The UA biosensor obtained by immobilizing the uricase enzyme (UrOx) onto the Pd/Au/PMMA/PET electrode surface, allowed UA detection with a sensitivity of 431 mu A cm(-2) mM(-1) and a limit of detection of 12 mu M. Investigation of the redox reactions of hydrogen peroxide (a product of the enzymatic oxidation of UA by UrOx) at the Pd/Au/PMMA/PET electrode demonstrated that the working principle of the biosensor is based on the reduction of PdO produced at the electrode surface during the spontaneous reduction of hydrogen peroxide on Pd. This allows a biosensor operating potential of -0.05 V (vs Ag/AgCl) with high selectivity. The UrOx/Pd/Au/PMMA/PET biosensor was applied for UA detection in body fluids (sweat, urine, and blood serum) with recovery values between 98 and 105%, which were validated by high-performance liquid chromatography analysis. The stability of the device was evaluated over a period of 3 months, retaining 78% of the initial sensitivity, and reproducibility with RSD = 4.9% was achieved. The analytical performance of the biosensor under harsh mechanical deformations and at physiological temperatures demonstrated the potential applications of the device to wearable sensing platforms.
2. Palladium-Coated Submicron Electrospun Polymeric Fibers with Immobilized Uricase for Uric Acid Determination in Body Fluids
Authors:
Leote, RJB; Crisan, DN; Matei, E; Enculescu, I; Diculescu, VC
Published: FEB 12 2024, ACS APPLIED POLYMER MATERIALS, 6, DOI: 10.1021/acsapm.3c02811
This work describes the development of a flexible uric acid (UA) biosensor based on palladium-coated submicrometer electrospun poly(methylmethacrylate) (PMMA) fibers metalized with gold and attached to polyethylene terephthalate substrate (Pd/Au/PMMA/PET). The morphological characterization conducted by scanning electron microscopy revealed nanoscale Pd dendritic structures. Electrochemical investigations in the absence and in the presence of redox probes demonstrated that these Pd nanostructures are responsible for a six-fold increase in the electroactive area and enhanced electron transfer kinetics when compared to the gold-coated electrospun fibers. The UA biosensor obtained by immobilizing the uricase enzyme (UrOx) onto the Pd/Au/PMMA/PET electrode surface, allowed UA detection with a sensitivity of 431 mu A cm(-2) mM(-1) and a limit of detection of 12 mu M. Investigation of the redox reactions of hydrogen peroxide (a product of the enzymatic oxidation of UA by UrOx) at the Pd/Au/PMMA/PET electrode demonstrated that the working principle of the biosensor is based on the reduction of PdO produced at the electrode surface during the spontaneous reduction of hydrogen peroxide on Pd. This allows a biosensor operating potential of -0.05 V (vs Ag/AgCl) with high selectivity. The UrOx/Pd/Au/PMMA/PET biosensor was applied for UA detection in body fluids (sweat, urine, and blood serum) with recovery values between 98 and 105%, which were validated by high-performance liquid chromatography analysis. The stability of the device was evaluated over a period of 3 months, retaining 78% of the initial sensitivity, and reproducibility with RSD = 4.9% was achieved. The analytical performance of the biosensor under harsh mechanical deformations and at physiological temperatures demonstrated the potential applications of the device to wearable sensing platforms.
3. Magnetic Memory Effects in BaFe2(As0.68P0.32)2 Superconducting Single Crystal
Authors:
Badea, AM; Ivan, I; Miclea, CF; Crisan, DN; Galluzzi, A; Polichetti, M; Crisan, A
Published: NOV 2024, MATERIALS, 17, 5340, DOI: 10.3390/ma17215340
Among many iron-based superconductors, isovalently substituted BaFe2(As1-xPx)2 displays, for x approximate to 0.3, apart from the quite usual Second Magnetization Peak (SMP) in the field dependence of the critical current density, an unusual peak effect in the temperature dependence of the critical current density in the constant field, which is related to the rhombic-to-square (RST) structural transition of the Bragg vortex glass (BVG). By using multi-harmonic AC susceptibility investigations in three different cooling regimes-field cooling, zero-field cooling, and field cooling with measurements during warming up-we have discovered the existence of a temperature region in which there is a pronounced magnetic memory effect, which we attributed to the direction of the structural transition. The observed huge differences in the third harmonic susceptibility at low and high AC frequencies indicates the difference in the time-scale of the structural transition in comparison with the timescale of the vortex excitations. Our findings show that the RST influence on the vortex dynamics goes beyond the previously observed influence on the onset of the SMP.
4. Vortex Glass-Vortex Liquid Transition in BaFe2(As1-xPx)(2) and CaKFe4As4 Superconductors from Multi-Harmonic AC Magnetic Susceptibility Studies
Authors:
Ivan, I; Ionescu, AM; Crisan, DN; Crisan, A
Published: APR 26 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 7896, DOI: 10.3390/ijms24097896
For practical applications of superconductors, understanding the vortex matter and dynamics is of paramount importance. An important issue in this context is the transition of the vortex glass, which is a true superconducting phase, into a vortex liquid phase having a linear dissipation. By using multi-harmonic susceptibility studies, we have investigated the vortex glass-vortex liquid phase transitions in CaKFe4As4 and BaFe2(As0.68P0.32)(2) single crystals. The principle of our method relates the on-set of the third-harmonic susceptibility response with the appearance of a vortex-glass phase in which the dissipation is non-linear. Similar to the high-critical temperature cuprate superconductors, we have shown that even in these iron-based superconductors with significant lower critical temperatures, such phase transition can be treated as a melting in the sense of Lindemann's approach, considering an anisotropic Ginzburg-Landau model. The experimental data are consistent with a temperature-dependent London penetration depth given by a 3D XY fluctuations model. The fitting parameters allowed us to extrapolate the vortex melting lines down to the temperature of liquid hydrogen, and such extrapolation showed that CaKFe4As4 is a very promising superconducting material for high field applications in liquid hydrogen, with a melting field at 20 K of the order of 100 T.
6. Vortex Glass-Vortex Liquid Transition in BaFe2(As1-xPx)2 and CaKFe4As4 Superconductors from Multi-Harmonic AC Magnetic Susceptibility Studies
Authors:
Ivan, I; Ionescu, AM; Crisan, DN; Crisan, A
Published: APR 26 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 7896, DOI: 10.3390/ijms24097896
For practical applications of superconductors, understanding the vortex matter and dynamics is of paramount importance. An important issue in this context is the transition of the vortex glass, which is a true superconducting phase, into a vortex liquid phase having a linear dissipation. By using multi-harmonic susceptibility studies, we have investigated the vortex glass-vortex liquid phase transitions in CaKFe4As4 and BaFe2(As0.68P0.32)(2) single crystals. The principle of our method relates the on-set of the third-harmonic susceptibility response with the appearance of a vortex-glass phase in which the dissipation is non-linear. Similar to the high-critical temperature cuprate superconductors, we have shown that even in these iron-based superconductors with significant lower critical temperatures, such phase transition can be treated as a melting in the sense of Lindemann's approach, considering an anisotropic Ginzburg-Landau model. The experimental data are consistent with a temperature-dependent London penetration depth given by a 3D XY fluctuations model. The fitting parameters allowed us to extrapolate the vortex melting lines down to the temperature of liquid hydrogen, and such extrapolation showed that CaKFe4As4 is a very promising superconducting material for high field applications in liquid hydrogen, with a melting field at 20 K of the order of 100 T.
7. Vortex Dynamics and Pinning in CaKFe4As4 Single Crystals from DC Magnetization Relaxation and AC Susceptibility
Authors:
Ionescu, AM; Ivan, I; Miclea, CF; Crisan, DN; Galluzzi, A; Polichetti, M; Crisan, A
Published: DEC 2023, CONDENSED MATTER, 8, 93, DOI: 10.3390/condmat8040093
Among various "families" of iron-based superconductors, the quite recently discovered AeAFe(4)As(4) (where Ae is an alkali-earth metal and A is an alkali metal) has high critical current density, a very high upper critical field, and a low anisotropy, and has recently received much interest for the possibility of high magnetic field applications at the liquid hydrogen temperature. We have performed DC magnetization relaxation and frequency-dependent AC susceptibility measurements on high-quality single crystals of CaKFe4As4 with the aim of determining the pinning potential U*. The temperature dependence of U* displays a clear crossover between elastic creep and plastic creep. At temperatures around 27-28 K, U* has a very high value, up to 1200 K, resulting in an infinitesimally small probability of thermally activated flux jumps. From the dependence of the normalized pinning potential on irreversible magnetization, we have determined the creep exponents in the two creep regimes, which are in complete agreement with theoretical models. The estimation of the pinning potential from multifrequency AC susceptibility measurements was possible only near the critical temperature due to equipment limitations, and the resulting value is very close to the one that resulted from the magnetization relaxation data. Magnetic hysteresis loops revealed a second magnetization peak and very high values of the critical current density.
8. Bioconjugates of mercaptocarboxylic acids functionalized AuNP and superoxide dismutase for superoxide electrochemical monitoring
Authors:
Sanz, CG; Crisan, DN; Leote, RJB; Onea, M; Barsan, MM
Published: JUL 2022, MICROCHIMICA ACTA, 189, 245, DOI: 10.1007/s00604-022-05352-z
The use of gold nanoparticles/superoxide dismutase (AuNP/SOD) bioconjugates is described as building blocks in SOD biosensor development for the quantification of superoxide in cell culture media. AuNP functionalization with 11-mercaptoundecanoic acid (MUA) and 4-mercaptobenzoic acid (MBA) (AuNPMUA and AuNPMBA) was used to improve SOD immobilization through EDC/NHS coupling using their -COOH terminus, leading to the formation of more stable bioconjugates. AuNP and AuNP/SOD bioconjugates were characterized by SEM to determine their size and morphology, UV-Vis for optical properties, FT-IR, and Raman spectroscopies for chemical functional group analysis and EDX for elemental analysis. Electrochemical methods were used to characterize the Au/AuNP-modified electrodes. For the optimization of the biosensor architecture, different AuNP/enzyme bioconjugates were prepared by varying the amount of both enzyme and AuNP, as well as their incubation time. Finally, the biosensors incorporating the bioconjugates were characterized by fixed potential amperometry and voltammetric analysis in order to establish the enzymatic mechanism and to elucidate the best biosensor architecture for monitoring superoxide in cell culture media. The best sensitivity value for superoxide detection corresponded to 41.2 nA mu M cm(-2), achieved by a biosensor based on AuNPMBA/SOD bioconjugates monitored through fixed potential amperometry at 0.3 V vs. Ag/AgCl, with a limit of detection of 1.0 mu M, and overall very good operational stability, maintaining 91% of the initial sensitivity after 30 days. Finally, the optimized biosensor was employed for the quantification of successive additions of superoxide in cell culture media, with excellent recovery values.
9. Pinning Potential of the Self-Assembled Artificial Pinning Centers in Nanostructured YBa2Cu3O7-x Superconducting Films
Authors:
Ivan, I; Ionescu, AM; Crisan, DN; Andrei, A; Galluzzi, A; Polichetti, M; Mosqueira, J; Crisan, A
Published: MAY 2022, NANOMATERIALS, 12, 1713, DOI: 10.3390/nano12101713
For high-field power applications of high-temperature superconductors, it became obvious in recent years that nano-engineered artificial pinning centers are needed for increasing the critical current and pinning potential. As opposed to the artificial pinning centers obtained by irradiation with various particles, which is a quite expensive approach, we have studied superconducting samples having self-assembled defects, created during the sample fabrication, that act as effective pinning centers. We introduced a simple, straight-forward method of estimating the frequency-dependent critical current density by using frequency-dependent AC susceptibility measurements, in fixed temperatures and DC magnetic fields, from the positions of the maxima in the dependence of the out-of-phase susceptibility on the amplitude of AC excitation magnetic field. The results are compatible with a model that stipulates a logarithmic dependence of the pinning potential on the probing current. A mathematical derivation allowed us to estimate from the experimental data the pinning potentials in various samples, and in various DC magnetic fields. The resulted values indicate large pinning potentials, leading to very small probability of magnetic flux escaping the pinning wells, hence, leading to very high critical currents in high magnetic fields.
10. Detailed Molecular and Structural Analysis of Dual Emitter IrQ(ppy)(2) Complex
Authors:
Ciobotaru, IC; Crisan, DN; Sket, P; Ciobotaru, CC; Polosan, S
Published: APR 2020, MATERIALS, 13, DOI: 10.3390/ma13071617
The molecular structure of the 8-hydroxyquinoline-bis (2-phenylpyridyl) iridium (IrQ(ppy)(2)) dual emitter organometallic compound is determined based on detailed 1D and 2D nuclear magnetic resonance (NMR), to identify metal-ligands coordination, isomerization and chemical yield of the desired compound. Meanwhile, the extended X-ray absorption fine structure (EXAFS) was used to determine the interatomic distances around the iridium ion. From the NMR results, this compound IrQ(ppy)(2) exhibits a trans isomerization with a distribution of coordinated N-atoms in a similar way to facial Ir(ppy)(3). The EXAFS measurements confirm the structural model of the IrQ(ppy)(2) compound where the oxygen atoms from the quinoline ligands induce the splitting of the next-nearest neighboring C in the second shell of the Ir3+ ions. The high-performance liquid chromatography (HPLC), as a part of the detailed molecular analysis, confirms the purity of the desired IrQ(ppy)(2) organometallic compound as being more than 95%, together with the progress of the chemical reactions towards the final compound. The theoretical model of the IrQ(ppy)(2), concerning the expected bond lengths, is compared with the structural model from the EXAFS and XRD measurements.
11. Different-Length Hydrazone Activated Polymers for Plasmid DNA Condensation and Cellular Transfection
Authors:
Priegue, JM; Lostale-Seijo, I; Crisan, D; Granja, JR; Fernandez-Trillo, F; Montenegro, J
Published: JUL 2018, BIOMACROMOLECULES, 19, 2649, DOI: 10.1021/acs.biomac.8b00252
The recent advances in genetic engineering demand the development of conceptually new methods to prepare and identify efficient vectors for the intracellular delivery of different nucleotide payloads ranging from short single-stranded oligonucleotides to larger plasmid double-stranded circular DNAs. Although many challenges still have to be overcome, polymers hold great potential for intracellular nucleotide delivery and gene therapy. We here develop and apply the postpolymerization modification of polyhydrazide scaffolds, with different degree of polymerization, for the preparation of amphiphilic polymeric vehicles for the intracellular delivery of a circular plasmid DNA. The hydrazone formation reactions with a mixture of cationic and hydrophobic aldehydes proceed in physiologically compatible aqueous conditions, and the resulting amphiphilic polyhydrazones are directly combined with the biological cargo without any purification step. This methodology allowed the preparation of stable polyplexes with a suitable size and zeta potential to achieve an efficient encapsulation and intracellular delivery of the DNA cargo. Simple formulations that performed with efficiencies and cell viabilities comparable to the current gold standard were identified. Furthermore, the internalization mechanism was studied via internalization experiments in the presence of endocytic inhibitors and fluorescence microscopy. The results reported here confirmed that the polyhydrazone functionalization is a suitable strategy for the screening and identification of customized polymeric vehicles for the delivery of different nucleotide cargos.
12. Sol-gel doped TiO2 nanomaterials: a comparative study
Authors:
Raileanu, M; Crisan, M; Dragan, N; Crisan, D; Galtayries, A; Braileanu, A; Ianculescu, A; Teodorescu, VS; Nitoi, I; Anastasescu, M
Published: SEP 2009, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 51, 329, DOI: 10.1007/s10971-009-2017-z
Among the great number of sol-gel prepared nanomaterials, TiO2 has attracted significant interest due to its high photocatalytic activity, excellent functionality, thermal stability and non-toxicity. The photocatalytic degradation of pollutants using un-doped and doped TiO2 nanopowders or thin films is very attractive for applications in environmental protection, as a possible solution for water purification. The present work describes a comparative structural and chemical study of un-doped TiO2 and the corresponding S- and Ag-doped materials. The photocatalytic activity was established by testing the degradation of organic chloride compounds from aqueous solutions. Sol-gel Ag-doped TiO2 coatings, prepared by co-gelation and sol-gel Ag-doped TiO2 coatings obtained from nanopowders were also compared. Their structural evolution and crystallization behaviour (lattice parameters, crystallite sizes, internal strains) with thermal treatment were followed by thermal analysis, X-ray diffraction, transmission electron microscopy, atomic force microscopy and specific surface areas measurements. X-ray photoelectron spectroscopy analyses were performed to characterize the surface composition and S or Ag speciation, which was used to interpret the catalytic data.
13. Thermal behaviour study of some sol-gel TiO2 based materials
Authors:
Crisan, M; Braileanu, A; Crisan, D; Raileanu, M; Dragan, N; Mardare, D; Teodorescu, V; Ianculescu, A; Birjega, R; Dumitru, M
Published: APR 2008, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 92, 13, DOI: 10.1007/s10973-007-8720-5
Among the great number of sol-gel materials prepared, TiO2 holds one of the most important places due to its photocatalytic properties, both in the case of powders and coatings. Impurity doping is one of the typical approaches to extend the spectral response of a wide band gap semiconductor to visible light. This work has studied some un-doped and Pd-doped sol-gel TiO2 nanopowders, presenting various surface morphologies and structures. The obtained powders have been embedded in vitreous TiO2 matrices and the corresponding coatings have been prepared by dipping procedure, on glass substrates. The relationship between the synthesis conditions and the properties of titania narrosized materials, such as thermal stability, phase composition, crystallinity, morphology and size of particles, and the influence of dopant was investigated. The influence of Pd on TiO2 crystallization both for supported and unsupported materials was studied (lattice parameters, crystallite sizes, internal strains). The hydrophilic properties of the films were also connected with their structure, composition and surface morphology. The methods used for the characterization of the materials have been: simultaneous thermogravimetry and differential thermal analysis, powder X-ray diffraction, electron microscopy (TEM, SAED) and AFM.
14. TiO2-based nanopowders obtained from different Ti-alkoxides
Authors:
Crisan, M; Braileanu, A; Raileanu, M; Crisan, D; Teodorescu, VS; Birjega, R; Marinescu, VE; Madarasz, J; Pokol, G
Published: APR 2007, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 88, 176, DOI: 10.1007/s10973-006-8125-x
Pure TiO2 and S-doped TiO2 sol-gel nanopowders were prepared by controlled hydrolysis-condensation of titanium alkoxides. The influence of different Ti-alkoxides (tetraethyl-, tetraisopropyl- and tetrabutyl-orthotitanate) used in obtaining TiO2 porous materials in similar conditions (water/alkoxide ratio, solvent/alkoxide ratio, pH and temperature of reaction) has been investigated. The relationship between the synthesis conditions and the properties of titania nanosized powders, such as thermal stability, phase composition, crystallinity, morphology and size of particles, BET surface area and the influence of dopant was investigated. The nature of the alkyl group strongly influences the main characteristics of the obtained oxide powders, fact which is pointed out by thermal analysis, X-ray diffraction, TEM and BET surface area measurements.
15. IR SPECTROSCOPIC MEASUREMENTS OF CRYSTALLINITY AND PHASE PURITY OF ZSM-5 SAMPLES
Authors:
FRUNZA, L; DINCA, V; VAGAON, M; CRISAN, D; FLORESCU, I; MANOIU, D; CRISAN, M; RAGAN, N
Published: MAR 1993, REVUE ROUMAINE DE CHIMIE, 38, 246, DOI:
The use of IR spectroscopic method to choose the best batches of ZSM-5 zeolites. is discussed. The crystallinity and the particle size were estimated from IR spectra and by XRD and electron microscopy measurements.
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