A dramatic rise in research interest in laser‐induced graphene oxide (GO) reduction and modification requires an overview of the most recent works on this subject. Typical methods for the recognition ...and confirmation of modified graphene and its derivatives, such as Raman, Fourier‐transform infra‐red (FTIR), X‐ray photoelectron (XP), and ultraviolet‐visible (UV–vis) spectroscopies, are introduced briefly in this review. A major part of the survey is devoted to the main modification ways and the laser parameters used in the literature. A discussion of possible reduction and modification mechanisms is also presented. Recent applications, especially in the biomedical field such as cell therapy treatment, as well as significant results of GO modification, are discussed in detail. Finally, perspectives for the application of laser‐induced GO modifications in passive THz photonics and biomedicine are briefly addressed.
Laser‐induced graphene oxide reduction: Lasers are often used for the effective and well‐controlled reduction of graphene oxide. Chemical graphene modification is easily performed online with laser‐induced graphene oxide reduction, changing the ambient conditions by adding required chemical compounds. Such photoreduced and modified graphene has a broad variety of applications in various fields from devices to sensors and medicine.
The unprecedented emergence of perovskite‐based solar cells (PSCs) has been accompanied by an intensive search of suitable materials for charge‐selective contacts. For the first time a ...hole‐transporting self‐assembled monolayer (SAM) as the dopant‐free hole‐selective contact in p–i–n PSCs is used and a power conversion efficiency of up to 17.8% with average fill factor close to 80% and undetectable parasitic absorption is demonstrated. SAM formation is achieved by simply immersing the substrate into a solution of a novel molecule V1036 that binds to the indium tin oxide surface due to its phosphonic anchoring group. The SAM and its modifications are further characterized by Fourier‐transform infrared and vibrational sum‐frequency generation spectroscopy. In addition, photoelectron spectroscopy in air is used for measuring the ionization potential of the studied SAMs. This novel approach is also suitable for achieving a conformal coverage of large‐area and/or textured substrates with minimal material consumption and can potentially be extended to serve as a model system for substrate‐based perovskite nucleation and passivation control. Further gains in efficiency can be expected upon SAM optimization by means of molecular and compositional engineering.
A novel concept for the formation of the hole selective layer in efficient perovskite solar cells is presented. Carbazole‐based material is synthesized and used for the formation of a self‐assembled monolayer on top of the indium tin oxide transparent conductive substrate. Power conversion efficiency as high as 17.8% is achieved.
Abstract
In the present work, gadolinium substitution effects on the properties of yttrium manganite Y
x
Gd
1−x
Mn
0.97
Fe
0.03
O
3
(x from 0 to 1 with a step of 0.2) synthesized by an aqueous ...sol–gel method have been investigated. Partial substitution of Mn
3+
by
57
Fe
3+
in the manganite was also performed in order to investigate deeper the structural properties of synthesized compounds applying Mössbauer spectroscopy. It was demonstrated that substitution of Y
3+
by Gd
3+
ions leads to the changes of structural, magnetic and morphological properties of investigated system. The crystal structure gradually transformed from hexagonal to orthorhombic with an increase of Gd
3+
content in the crystal lattice. The mixed phase was obtained when x = 0.6, whereas other compounds were determined to be monophasic. Magnetization measurements revealed paramagnetic behavior of all specimens, however magnetization values were found to be dependent on chemical composition of the samples. Solid solutions with orthorhombic structure revealed higher magnetization values compared to those of hexagonal samples. The highest magnetization was observed for pure GdMn
0.97
Fe
0.03
O
3
. Structural properties were investigated by powder X-ray diffraction, Mössbauer, FTIR and Raman spectroscopies. Morphological features of the synthesized specimens were studied by scanning electron microscopy (SEM).
We report a study of the determination of polymer cross‐linking, namely the degree of conversion and refractive index of the microstructures created by two‐photon polymerization (TPP). The influence ...of TPP processing parameters such as laser intensity and scanning velocity is investigated. The degree of conversion is analyzed via Raman microspectroscopy and the refractive index is measured with the interferometric technique employing a Michelson interferometer. Moreover, the relationship between these two properties is revealed and details are discussed. The largest refractive index change that we have obtained is of the order of 10−2. Finally, we propose and demonstrate experimentally the realization of the gradient‐index (GRIN) structure, resulting from a laser‐induced local refractive index modification due to monomer cross‐linking, i.e. degree of conversion. This work implies that the TPP technique is a valuable tool for the fabrication of GRIN microoptics for (in)homogeneous molding of light flow at the micrometer scale.
This paper demonstrates and promotes an innovative and original approach to the application of two‐photon photolithography in the field of gradient refractive index (RI) microoptics. It is focused on the tuning of RI of photopolymerizable microstructures by controlling the exposure conditions during fabrication. It is shown that RI is directly linked to the chemical properties (degree of conversion) of the material as determined using a Raman microspectroscopy technique.
Several neurodegenerative diseases, like Alzheimer's and Parkinson's are linked with protein aggregation into amyloid fibrils. Conformational changes of native protein into the β-sheet structure are ...associated with a significant change in the vibrational spectrum. This is especially true for amide bands which are inherently sensitive to the secondary structure of a protein. Raman amide bands are greatly intensified under resonance conditions, in the UV spectral range, allowing for the selective probing of the peptide backbone. In this work, we examine parallel β-sheet forming GGVVIA, the C-terminus segment of amyloid-β peptide, using UV-Vis, FTIR, and multiwavelength Raman spectroscopy. We find that amide bands are enhanced far from the expected UV range, i.e., at 442 nm. A reasonable two-fold relative intensity increase is observed for amide II mode (normalized according to the δCH
/δCH
vibration) while comparing 442 and 633 nm excitations; an increase in relative intensity of other amide bands was also visible. The observed relative intensification of amide II, amide S, and amide III modes in the Raman spectrum recorded at 442 nm comparing with longer wavelength (633/785/830 nm) excited spectra allows unambiguous identification of amide bands in the complex Raman spectra of peptides and proteins containing the β-sheet structure.
The imidazole ring (Im) of histidine side chains plays a unique role in the function of proteins through covalent bonding with metal ions and hydrogen bonding interactions with adjusted biomolecules ...and water. At biological interfaces, these interactions are modified because of the presence of an electric field. Self-assembled monolayers (SAMs) with the functional Im group mimic the histidine side chain at electrified interfaces. In this study, we applied in-situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) to probe the structure and hydrogen bonding of Im-functionalized SAM on smooth Au at the electrochemical interface. The self-assembly of molecules on the Au induced the proton shift from N1 atom (Tautomer-I), which is the dominant form of Im in the bulk sample, to N3 atom (Tautomer-II). The impact of electrode potential on the hydrogen bonding interaction strength of the Im ring was identified by SHINERS. Temperature-Raman measurements and density functional theory (DFT) analysis revealed the spectral marker for Im ring packing (mode near 1496–1480 cm−1) that allowed us to associate the confined and strongly hydrogen bonded interfacial Im groups with electrode polarization at −0.8 V. Reflection adsorption IR (RAIR) spectra of SAMs with and without Im revealed that the bulky ring prevented the formation of a strongly hydrogen bonded amide group network.
Effects of amyloid beta (Aβ) oligomers on viability and function of cell lines such as NB4 (human acute promyelocytic leukemia), A549 (human lung cancer (adenocarcinomic alveolar basal epithelial ...tumor)) and MCF-7 (human breast cancer (invasive breast ductal carcinoma)) were investigated. Two types of Aβ oligomers were used in the study. The first type was produced in the presence of oligomerization inhibitor, hexafluoroisopropanol (HFIP). The second type of amyloids was assembled in the absence of the inhibitor. The first type preparation was predominantly populated with dimers and trimers, while the second type contained mostly pentadecamers. These amyloid species exhibited different secondary protein structure with considerable amount of antiparallel β sheet structural elements in HFIP oligomerized Aβ mixtures. The effect of the cell growth inhibition, which was stronger in the case of HFIP Aβ oligomers, was observed for all cell lines. Tests aiming at elucidating the effects of the amyloid species on cell cycles showed little differences between amyloid preparations. This prompts us to conclude that the effect on the cancer cell proliferation rate is less specific to the biological processes developing inside the cells during the proliferation. Therefore, cell growth inhibition may involve interactions with the peripheral parts of the cancer cells, such as a phospholipid membrane, and only in case of the NB4 cells, where accumulation of amyloid species inside the cells was detected, one may imply the opposite. In general, cancer cells were much less susceptible to the damaging effects of amyloid oligomers compared to earlier observations in mixed neuronal cell cultures.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The surface of a polycrystalline roughened Cu electrode in 1 M NaOH solution, has been studied in situ using surface-enhanced Raman spectroscopy (SERS). Cu
2O, adsorbed OH
− ions, and water molecules ...have been detected as the electrode potential was varied from open circuit value to −1.20 V versus SHE. The vibrational spectrum of Cu
2O consisted of three main peaks located at 150, 528, and 623 cm
−1. It was found that the intense and narrow feature at 150 cm
−1 is highly characteristic, and could be used for SER monitoring of Cu
2O. Two different states of adsorbed OH
− ions, giving CuOH vibrations around 450–470 cm
−1 and 540–580 cm
−1, have been detected. The distinct nature of the bands has been shown by opposite isotopic frequency shifts changing the solvent from H
2O to D
2O. The frequency of the first band decreased by ∼12 cm
−1, while the frequency of the second band increased by ∼35 cm
−1 in D
2O solutions. These differences have been explained in terms of distinct surface ligation and the formation of strong hydrogen bonds between water molecules and the second type of adsorbed OH
− ion. Water molecules were observed at the interface at an applied potential −1.20 V.
An essential amino acid, histidine, has a vital role in the secondary structure and catalytic activity of proteins because of the diverse interactions its side chain imidazole (Im) ring can take part ...in. Among these interactions, hydrogen donating and accepting bonding are often found to operate at the charged interfaces. However, despite the great biological significance, hydrogen-bond interactions are difficult to investigate at electrochemical interfaces due to the lack of appropriate experimental methods. Here, we present a surface-enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) study addressing this issue. To probe the hydrogen-bond interactions of the Im at the electrified organic layer/water interface, we constructed Au-adsorbed self-assembled monolayers (SAMs) that are functionalized with the Im group. As the prerequisite for spectroelectrochemical investigations, we first analyzed the formation of the monolayer and the relationship between the chemical composition of SAM and its structure. Infrared absorption markers that are sensitive to hydrogen-bonding interactions were identified. We found that negative electrode polarization effectively reduced hydrogen-bonding strength at the Im ring at the organic layer–water interface. The possible mechanism governing such a decrease in hydrogen-bonding interaction strength is discussed.
Bismuth films with thicknesses between 6 and ∼30 nm were grown on Si (111) substrate by molecular beam epitaxy (MBE). Two main phases of bismuth — α-Bi and β-Bi — were identified from high-resolution ...X-ray diffraction (XRD) measurements. The crystal structure dependencies on the layer thicknesses of these films were analyzed. β-Bi layers were epitaxial and homogenous in lateral regions that are greater than 200 nm despite the layer thickness. Further, an increase in in-plane 2θ values showed the biaxial compressive strain. For comparison, α-Bi layers are misoriented in six in-plane directions and have β-Bi inserts in thicker layers. That leads to smaller (about 60 nm) lateral crystallites which are compressively strained in all three directions. Raman measurement confirmed the XRD results. The blue-sift of Raman signals compared with bulk Bi crystals occurs due to the phonon confinement effect, which is larger in the thinnest α-Bi layers due to higher compression.
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