Measurements Of Diffuse Reflectance Spectra Research Articles

Comparison study of the structure, dielectric function, and two-photon absorption cross-section of BiOI and Ag/BiOI nanomaterials

In this research, the interesting methods including X-ray diffraction (XRD) pattern, Field Emission Scanning Electron Microscopy (FESEM) images, energy dispersive X-ray (EDX), UV–Vis spectroscopy, Diffuse reflectance (DRS) spectrum, KK method, and Z-scan measurements were employed for characterizations of prepared BiOI and Ag/BiOI nanomaterials. The optical indices such as n, k, and ε1 and ε2 were assessed based on reflectance spectra data and the Kramers-Kronig (KK) method. Furthermore, the nonlinear optical (NLO) properties of prepared BiOI and Ag/BiOI nanomaterials in different Ag precents were examined through the Z-scan method using the laser beam at 532 nm wavelength. The two-photon absorption (TPA) and self-focusing performance are revealed by the prepared nanomaterials. Adding Ag into BiOI structures, significantly increases the TPA cross-section, σ2 which reaches up to 1.14578 × 10−21 cm4/W for the sample of S3. One of the significant factors that affected the improvement of the optical nonlinearity properties of Ag/BiOI and over BiOI was ascribed to the combined consequence of Ag's localized surface plasmon resonance (LSPR) phenomena, resulting in improved light absorption intensity coupling interaction, significant photo-produced electron-hole separability, and prolonged carrier lifetime.

Surfactant-induced photocatalytic performance enhancement of europium oxide nanoparticles

Recently, rare earth (RE) elements and their oxides have been attracting more and more attention in the field of photocatalytic degradation. Due to the unique 4 f electronic structure and optical properties, the RE element, europium (Eu), together with its oxides, are often used for surface modification of other photocatalysts. Nevertheless, the photocatalytic degradation property of europium oxide has been rarely reported. In this study, we synthesized Eu2O3 nanoparticles via chemical precipitation and calcination processes, and performed surface modification by using surfactants as polyvinyl pyrrolidone (PVP) and hexadecyl trimethyl ammonium bromide (CTAB). Compared with pure Eu2O3 nanoparticles and those synthesized with PVP, photocatalytic degradation efficiencies of Eu2O3 nanoparticles synthesized with surfactant CTAB for degrading rhodamine B dye demonstrated to be improved by 16% and 12%, respectively. The ultraviolet-visible diffuse reflectance spectra measurements indicate that CTAB can increase the bandgap of Eu2O3 due to the reduction of oxygen defects. Photoluminescence spectra demonstrate that the surfactant would affect the luminescence of Eu3+ and carrier redistribution of energy levels.

Insights into the Effects of Study Area Size and Soil Sampling Density in the Prediction of Soil Organic Carbon by Vis-NIR Diffuse Reflectance Spectroscopy in Two Forest Areas

Sustainable forest land management requires measuring and monitoring soil organic carbon. Visible and near-infrared diffuse reflectance spectroscopy (Vis-NIR, 350–2500 nm), although it has become an important method for predicting soil organic carbon (SOC), requires further studies and methods of analysis to realize its full potential. This study aimed to determine if the size of the study area and soil sampling density may affect the performance of Vis-NIR diffuse reflectance spectroscopy in the prediction of soil organic carbon. Two forest sites in the Calabria region (southern Italy), which differ in terms of area and soil sampling density, were used. The first one was Bonis catchment area (139 ha) with a cover consisting mainly of Calabrian pine, while the second was Mongiana forest area (33.2 ha) within the “Marchesale” Biogenetic Nature Reserve, which is covered by beech. The two study areas are relatively homogeneous regarding parent material and soil type, while they have very different soil sampling density. In particular, Bonis catchment has a lower sampling density (135 samples out of 139 ha) than Mongiana area (231 samples out of 33.2 ha). Three multivariate calibration methods (principal component regression (PCR), partial least square regression (PLSR), and support vector machine regression (SVMR)) were combined with different pretreatment techniques of diffuse reflectance spectra (absorbance, ABS, standard normal variate, SNV, and Savitzky–Golay filtering with first derivative (SG 1st D). All soil samples (0–20 cm) were analyzed in the laboratory for SOC concentration and for measurements of diffuse reflectance spectra in the Vis-NIR region. The set of samples from each study area was randomly divided into a calibration set (70%) and a validation set (30%). The assessment of the goodness for the different calibration models and the following SOC predictions using the validation sets was based on three parameters: the coefficient of determination (R2), the root mean square error (RMSE), and the interquartile range (RPIQ). The results showed that for the two study areas, different levels of goodness of the prediction models depended both on the type of pretreatment and the multivariate method used. Overall, the prediction models obtained with PLSR and SVMR performed better than those of PCR. The best performance was obtained with the SVMR method combined with ABS + SNV + SG 1st D pretreatment (R2 ≥ 0.77 and RPIQ > 2.30). However, there is no result that can absolutely provide definitive indications of either the effects of the study area size and soil sampling density in the prediction of SOC by vis-NIR spectroscopy, but this study fostered the need for future investigations in areas and datasets of different sizes from those in this study and including also different soil landscapes.

Characterization of TiO2 nanofibers with enhanced photocatalytic properties prepared by plasma assisted calcination

In this article, we present a novel approach to produce titania (TiO 2 ) nanofibers with enhanced properties using plasma pre-treatment. Nanofibers were produced from electro-spun polyvinylpyrrolidone (PVP) based nanofibers with titanium(IV) isopropoxide (TTIP) as a precursor. PVP/TTIP fibers were plasma treated using diffuse coplanar surface barrier discharge (DCSBD) followed by thermal calcination at 500 °C, 600 °C and 700 °C. The morphology of nanostructures was characterized using SEM, BET and XRD, the chemical composition was analyzed by XPS, ATR-FTIR, the photocatalytic activity was evaluated by degradation of methylene blue and band gap was determined from diffuse reflectance spectra (DRS) using Tauc plot. Initial plasma treatment caused decomposition of polymer matrix, which led to faster oxidation and crystalline phase transition at lower temperature during the following thermal processing/calcination. The results showed enhanced photocatalytic properties of plasma pre-treated fibers despite the fact they possess higher proportion of rutile and lower specific surface area. UV–vis DRS measurements exhibit lower band gap energy at 700 °C, but difference between plasma treated (PT) and non-treated (NT) samples at the same temperature was not observed.

Synthesis, structural characterization and in vitro antibacterial activity studies of ternary metal complexes of anti-inflammatory bromhexine drug

A novel d-block metal complexes of M(II)/(III) ions using bromhexine (BHX) as primary ligand and glycine (GLY) as secondary ligand were synthesized and characterized. The structures of these complexes were confirmed by different spectroscopic tools. From the molar conductivity, elemental analyses and thermal analysis data of the synthesized complexes, general formula of [M(BHX)(Gly)(H2O)2]XCl·yH2O, (where M = Cr(III), x = y = 2; Mn(II), Co(II), Ni(II), Cu(II) and Zn(II), x = 1, y = 0; Cd(II), x = 1, y = 2) and [Fe(BHX)(Gly)(H2O)Cl]Cl with an octahedral structure were proposed. The octahedral geometry was supported by the magnetic moment and diffuse solid reflectance spectra measurements. The IR spectra pointed out that BHX ligand coordinated in neutral bidentate mode to the metal ions while Gly coordinated in mono negative bidentate mode. Conductivity measurements revealed that the ternary complexes were electrolytes. The complexes were tested against a variety of pathogenic bacterial strains and shown to have effective antibacterial capabilities when compared to bromhexine, suggesting that they could be useful models for the development of effective antibiotic drug molecules. In addition, the ligands were tested for anticancer activity against the MCF-7 breast cancer cell line, and the results revealed that the metal complexes were more active than the parent BHX free ligand. The BHX ligand and Co(II) complex were molecular docked to a variety of potential biological targets, including the receptors of Staphylococcus aureus crystal structure (PDB ID: 4K3V) and the receptors of breast cancer mutant oxidoreductase (PDB ID: 3HB5).

Optical properties of Nd3+ ions in (Ca4Nb2)1-xNd2xO9–6x solid solution

The Ca4Nb2O9–xNd2O3 (where x = 0.1–1.0) pseudobinary samples were synthesized by the high-temperature solid state method. Optical properties of Nd3+ ions in this oxide system were studied and related to the structural phase transition dependent on the Nd2O3 oxide content. Structural and optical properties are discussed based on ATR IR, dielectric, diffuse reflectance and emission spectra measurements. The spectroscopic studies show a structural phase transition occurring for x = 0.5 and for which the initial limited solid solution transforms to the diphasic form of Ca2NdNbO6 and Nd2O3.

Impairments of cerebral blood flow microcirculation in rats brought on by cardiac cessation and respiratory arrest.

The impairments of cerebral blood flow microcirculation brought on by cardiac and respiratory arrest were assessed with multi-modal diagnostic facilities, utilising laser speckle contrast imaging, fluorescence spectroscopy and diffuse reflectance spectroscopy. The results of laser speckle contrast imaging show a notable reduction of cerebral blood flow in small and medium size vessels during a few minutes of respiratory arrest, while the same effect was observed in large sinuses and their branches during the circulatory cessation. Concurrently, the redox ratio assessed with fluorescence spectroscopy indicates progressing hypoxia, NADH accumulation and increase of FAD consumption. The results of diffuse reflectance spectra measurements display a more rapid grow of the perfusion of deoxygenated blood in case of circulatory impairment. In addition, consequent histopathological analysis performed by using new tissue staining procedure developed in-house. It shows notably higher reduction of size of the neurons due to their wrinkling within brain tissues influenced by circulation impair. Whereas, the brain tissues altered with the respiratory arrest demonstrate focal perivascular oedema and mild hypoxic changes of neuronal morphology. Thus, the study suggests that consequences of a cessation of cerebral blood flow become more dramatic and dangerous compare to respiratory arrest.

Synthesis and enhanced bias-free photoelectrochemical water-splitting activity of ferroelectric BaTiO3/Cu2O heterostructures under solar light irradiation

Here, we first use a facile electrochemical deposition method to load Cu2O nanoparticles onto the BaTiO3 (BTO) surface to prepare BTO/Cu2O heterostructure photoanodes. Compared to the pure BTO photoanode, all BTO/Cu2O heterostructure photoanodes show outstanding visible light harvesting ability and greatly improved photoelectrochemical water splitting performance. By optimizing the loading amount of Cu2O nanoparticles, the photocurrent density achieved by BTO/Cu2O-100 photoanode is 0.26 mA/cm2 at 0 V versus Ag/AgCl, which is 2.6 times that of the bare BTO photoanode. In contrast with the photocurrent densities of the other reported BTO-based heterostructure photoanodes, the photocurrent density achieved by the present BTO/Cu2O-100 photoanode without bias voltage is much higher. Additionally, the maximum solar-to-hydrogen conversion efficiency of the BTO/Cu2O-100 heterostructure photoanode is 0.11% at 0.72 V versus reversible hydrogen electrode, approximately double that of BTO photoanode. The measurements of diffuse reflectance spectra, photoelectrochemical impedance and the room temperature photoluminescence spectra demonstrate that the improved photoelectrochemical performance contributes from the visible light absorption ability of Cu2O nanoparticles, efficient transport and separation of photogenerated electron-hole pairs, which are induced by the spontaneous polarization electric field of ferroelectric BTO, p-n junction and type-II band alignment of BTO/Cu2O heterostructure photoanode. A possible mechanism for the improved photoelectrochemical water splitting performance and charge transfer process is proposed.

Metal–organic frameworks derived C/TiO2 for visible light photocatalysis: Simple synthesis and contribution of carbon species

A series of in-situ carbon-doped TiO2 (Cx/TiO2) composites with a porous and crystalline structure were successfully synthesized via one-step and low-temperature calcination of titanium metal–organic framework (MOF), MIL-125(Ti). The resultant materials were comprehensively investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption measurements, UV–vis diffuse reflectance spectrum (DRS), photoluminescence (PL) spectra and photoelectrochemical measurements, and their photocatalytic activities for bisphenol A (BPA) degradation were assessed. Compared with the benchmark TiO2 photocatalyst (P25), the Cx/TiO2 composite material with high specific surface, lower band gap, and reduced photogenerated electron hole ratio exhibited outstanding photodegradation activity and durability for BPA, which could be attributed to the combined effect of co-doping of multiple carbon species (substituent carbon and carbonate) and porous structure. During BPA degradation, the holes and superoxide radicals were the primary role oxidative species in the reaction process. Therefore, this new efficient photocatalyst is promising candidate for photodegradation of organic pollutants.

Facile synthesis of rGO-supported AgI-TiO2 mesocrystals with enhanced visible light photocatalytic activity

Facile synthesis of novel rGO-supported AgI decorated TiO2 mesocrystals (AgI-TMCs-rGO) and their photocatalytic activity under visible light irradiation are reported. The catalysts were prepared by combining the hydrothermal reaction process and in situ deposition–precipitation method. The structural features and chemical compositions of the prepared catalysts were investigated by HRTEM (high resolution transmission electron microscopy), XRD (x-ray powder diffraction), Raman spectra, XPS (x-ray photoelectron spectroscopy), UV–vis DRS (UV–vis diffuse reflectance spectra), PLS (photoluminescence spectra), and N2 physisorption measurements. The AgI-TMCs-rGO catalysts featured a large surface area, high adsorption capacity, enhanced photo-induced charge separation and strong absorbance of visible light. The intimate contact of various components and the fast transfer of charge carriers effectively suppresses photolysis of AgI and favors the structural stability of AgI-TMCs-rGO. The photocatalytic activity of the catalysts was evaluated by degrading Rhodamine B (RhB) in an aqueous solution under visible light irradiation. The highest photocatalytic activity was observed in the sample 20%Ag-TMCs-rGO, attributed to the synergistic effects of a lower band gap and a lowerrecombination rate of the charge carriers, along with the larger surface area of the fabricated sample.

Retraction Note to: Fabrication and characterization of Mg3Y2Ga3O12:Bi3+/TiO2-based UV fluorescent composition for improving the heavy oil viscosity reduction

Luminescent materials have been extensively explored in the past years for use in white LEDs, considering that previous works have paid little attention to it for other promising applications such as catalysts and water purification. Here we prepared a type of UV luminescent Mg3Y2Ga3O12:Bi3+ phosphor. To characterize the photoluminescence (PL) and structural properties, the Mg3Y2Ga3O12:Bi3+ samples have been recorded by the measurements of XRD, SEM, diffuse reflectance and PL spectra. The XRD and SEM results show that the Mg3Y2Ga3O12:Bi3+ samples belong to an inverse garnet cubic structure with a space group of Ia3d (No. 230) and distribute the particle size at about 30 μm. The PL spectra reveal that the Mg3Y2Ga3O12:Bi3+ samples can only show one emission band at around 350 nm, which can precisely cover over the whole UV spectral region from 290 nm to 410 nm. In view of this PL behavior and the TiO2 absorption band at around 387 nm, we design a type of ceramic substrate, i.e., Mg3Y2Ga3O12:Bi3+/TiO2-based composition, by mixing Mg3Y2Ga3O12:Bi3+ and TiO2. As a result, the photocatalytic properties of Mg3Y2Ga3O12:Bi3+/TiO2-based composition under 254 nm UV irradiation is found to enhance the heavy oil viscosity reduction about ~ 4 times as compared to that of TiO2 and bulk heavy oil.

In-situ ionothermal precipitation of well-dispersed ZnO nanoparticles onto 2-dimension neat graphene sheets with excellent photocatalytic activity

Neat graphene (NG) is rarely selected as a support to improve the photocatalytic performance of metal oxides due to its extremely poor processability in aqueous solutions. In this study, an in-situ ionothermal precipitation was developed to fabricate ZnO nanoparticle and few-layered NG sheet nanohybrids (ZnO/NG) in one-pot. Choline chloride/diethylene glycol-based deep eutectic solvent was used as reaction medium to dissolve the zinc salt precursor and disperse graphene. XRD, Raman, XPS and TEM analyses showed that ZnO particles with sizes of 15–25 nm were uniformly dispersed on the graphene sheets and a bond of ZnOC was formed between the interfaces. The UV–vis diffuse reflectance spectra measurement exhibited that the incorporation of graphene slightly narrowed the bandgap of ZnO nanoparticles, but significantly enhanced the light absorption of the nanohybrids in the visible range. Photocatalytic degradation of methylene blue dye evidenced that ZnO/NG offered excellent photocatalytic performance, regardless of UV or visible light irradiation. Under UV light, graphene as an electron transporter effectively promoted the separation of photogenerated carriers, while under visible light graphene was sensitized from the ground-state to the excited-state. The resulting electrons were injected into the conduction band of ZnO to transform wide bandgap ZnO into a photocatalyst driven by visible light. This work provided a green and simple method to prepare ZnO/NG nanohybrids with efficient and stable photocatalytic performance for water pollution remediation.

Photocatalytic degradation of organic dyes on Li-doped graphitic carbon nitrides

Lithium-doped graphitic carbon nitrides (g-C3N4) with varied lithium contents (i.e., Lir-CN) were synthesized using LiCl and melamine as precursors and then served as catalysts for photocatalytic degradation of dyes in aqueous solution. The samples were characterized by X-ray diffraction patterns, infrared spectroscopy, N2 physisorption isotherms, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectrum, Photoluminescence, and photocurrent measurements. Results indicated that the Li doping slightly increases the surface area and pore size, lowers the band gap, and improves the electron–hole separation efficiency, and in particular, results in the formation of polytriazineimide, which can cooperate with g-C3N4 and yield synergistic contribution to the reaction. Catalytic tests showed that the Li doping enhances the activity of g-C3N4 for photocatalytic degradation of rhodamine B (RhB), with the optimal efficiency obtained at molar ratio of LiCl to melamine equals to 0.5, i.e., Li0.5-CN, which exhibited 93.4% RhB conversion within 30 min. Moreover, Li0.5-CN is also highly active for the removal of other organic dyes, such as methyl orange and methylene blue, potentiating its promising applications for the removal of dyes in complex environment.

RETRACTED ARTICLE: Fabrication and characterization of Mg3Y2Ga3O12:Bi3+/TiO2-based UV fluorescent composition for improving the heavy oil viscosity reduction

Luminescent materials have been extensively explored in the past years for use in white LEDs, considering that previous works have paid little attention to it for other promising applications such as catalysts and water purification. Here we prepared a type of UV luminescent Mg3Y2Ga3O12:Bi3+ phosphor. To characterize the photoluminescence (PL) and structural properties, the Mg3Y2Ga3O12:Bi3+ samples have been recorded by the measurements of XRD, SEM, diffuse reflectance and PL spectra. The XRD and SEM results show that the Mg3Y2Ga3O12:Bi3+ samples belong to an inverse garnet cubic structure with a space group of Ia3d (No. 230) and distribute the particle size at about 30 μm. The PL spectra reveal that the Mg3Y2Ga3O12:Bi3+ samples can only show one emission band at around 350 nm, which can precisely cover over the whole UV spectral region from 290 nm to 410 nm. In view of this PL behavior and the TiO2 absorption band at around 387 nm, we design a type of ceramic substrate, i.e., Mg3Y2Ga3O12:Bi3+/TiO2-based composition, by mixing Mg3Y2Ga3O12:Bi3+ and TiO2. As a result, the photocatalytic properties of Mg3Y2Ga3O12:Bi3+/TiO2-based composition under 254 nm UV irradiation is found to enhance the heavy oil viscosity reduction about ~ 4 times as compared to that of TiO2 and bulk heavy oil.

Synthesis and characterization of black TiO2 nanoparticles by pulsed laser irradiation in liquid

Modified TiO2 (black TiO2) nanoparticles (NPs) produced by different methods showed enhanced visible light absorption than ordinary white TiO2 NPs. Pulsed laser ablation in liquid (PLAL) is a promising technique for synthesizing nanostructures due to its simplicity, less usage of toxic reagents and absence of costly vacuum systems. In the present study, black TiO2 NPs synthesized by pulsed laser irradiation is examined for their structure, morphology and optical properties. Nanoparticles of modified TiO2 were prepared by pulsed laser ablation in liquid technique by irradiating white TiO2 powder in water using an Nd:YAG laser (532 nm, 10 ns, 10 Hz). Characterization of morphology of the nanoparticles by scanning electron microscopy (SEM) showed a change in morphology by laser irradiation for TiO2 nanoparticles. Crystalline structure was determined by X-ray diffraction (XRD) in which the major anatase phase in white TiO2 was changed to rutile during irradiation and for longer irradiation, rutile became the major phase. Most of the vibrational peaks for TiO2 were identified in Raman spectra. Ti 2p and O 1s binding energy analysis by X-ray photoelectron spectroscopy (XPS) for black TiO2 (90 min) showed changes of 0.5 eV and 0.7 eV respectively compared to the white TiO2 due to their change in chemical states. Optical absorption and band gap evaluation were done using the diffuse reflectance spectra measurements that showed enhanced absorption in the visible range for all the laser irradiated nanoparticles and a decrease in the bandgap from 2.98 eV of white TiO2 to 1.84 eV for black TiO2. Synthesis of black TiO2 at normal atmospheric conditions by irradiation of TiO2 in liquid using 532 nm laser output which is a very common Nd:YAG wavelength is reported for the first time.

$$\hbox {Sn}^{4+}$$ Sn 4 + -doped $$\hbox {TiO}_{2}$$ TiO 2 nanorod array film with enhanced visible light photocatalytic activity

$$\hbox {Sn}^{4+}$$ -doped $$\hbox {TiO}_{2}$$ nanorod array film (NAF) on the fluorine-doped tin oxide (FTO) conducting glass was successfully synthesized using the facile hydrothermal method. The NAF photocatalysts were characterized by the scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–Vis diffuse reflectance spectra (DRS). The SEM images showed that both doped and pure $$\hbox {TiO}_{2}$$ NAFs exhibited a good nanorod array structure. $$\hbox {Sn}^{4+}$$ -doped $$\hbox {TiO}_{2}$$ NAF still maintains rutile crystal structure, which was identical to that of pure $$\hbox {TiO}_{2}$$ sample. By means of the DRS measurement, it was found that the $$\hbox {Sn}^{4+}$$ doping in $$\hbox {TiO}_{2}$$ nanorod could induce an obvious enhancement of visible light absorption owing to the introduction of doping energy level in the band gap of $$\hbox {TiO}_{2}$$ . The degradation of methyl orange (MO) demonstrated that the $$\hbox {Sn}^{4+}$$ -doped $$\hbox {TiO}_{2}$$ NAF exhibited an enhanced photocatalytic activity than pure $$\hbox {TiO}_{2}$$ NAF under the visible light ( $$\lambda >400\;\hbox {nm}$$ ) irradiation, which should be attributed to the enhanced visible light response and improved separation efficiency of photogenerated carriers of $$\hbox {Sn}^{4+}$$ -doped $$\hbox {TiO}_{2}$$ .

Crystal structures and theoretical studies of polyphosphate LiZnP3O9 for nonlinear optical applications

Nonlinear optical materials have attracted worldwide attention owing to their wide range of applications, specially in the laser field. Phosphates with noncentrosymmetric structures are potential candidates for novel ultraviolet (UV)-NLO materials, because they usually display short UV cut-off edges. In this work, a polyphosphate, the LiZnP3O9 polyphosphate crystals were grown through spontaneous crystallization from high-temperature melts. It crystallizes in the orthorhombic space group P212121 with unit cell parameters a = 8.330(3) Å, b = 8.520(3) Å, c = 8.635(3) Å, and Z = 4. In the structure, all the P atoms are coordinated by four oxygen atoms forming the [PO4] tetrahedra and further connected to generate a zig-zag [PO3]∞ anionic framework. Thermal analysis, IR spectroscopy, UV–vis–NIR diffuse reflectance spectrum and powder second harmonic generation measurements are performed. In addition, the first-principles calculation was employed for better understanding the structure–property relationships of LiZnP3O9.

Pb4(BO3)2(SO4) and Pb2[(BO2)(OH)](SO4): New lead(II) borate-sulfate mixed-anion compounds with two types of 3D network structures

Two new lead(II) borate-sulfate mixed-anion compounds, namely, Pb4(BO3)2(SO4) and Pb2[(BO2)(OH)](SO4), have been prepared by using high-temperature melt method or hydrothermal reaction. These compounds exhibit two different types of 3D structures composed of the same anionic units of BO3 triangles and SO4 tetrahedra which are interconnected by lead(II) cations. In Pb4(BO3)2(SO4), the lead(II) ions are bridged by borate anions into 3D [Pb4(BO3)2]2+ architectures with 1D tunnels of 8-member rings along the a-axis, which are filled by the sulfate anions. In Pb2[(BO2)(OH)](SO4), the lead(II) ions are interconnected by borate and sulfate anions into 2D Pb-B-O and Pb-S-O layers parallel to the ab plane, respectively, and these layers are further condensed into the 3D lead(II) borate-sulfate framework. TGA and DSC studies indicate that Pb4(BO3)2(SO4) is congruently melting with a melting point of 689 °C whereas Pb2[(BO2)(OH)](SO4) decomposes at approximately 335 °C. UV/Vis/NIR optical diffuse reflectance spectrum measurements reveal the optical band gaps of 4.03 and 4.08 eV for Pb4(BO3)2(SO4) and Pb2[(BO2)(OH)](SO4), respectively. Furthermore, the electronic structures of Pb4(BO3)2(SO4) have also been calculated.

Influence of probe pressure on diffuse reflectance spectra of human skin measured in vivo.

Mechanical pressure superficially applied on the human skin surface by a fiber-optic probe influences the spatial distribution of blood within the cutaneous tissues. Upon gradual load of weight on the probe, a stepwise increase in the skin reflectance spectra is observed. The decrease in the load follows the similar inverse staircase-like tendency. The observed stepwise reflectance spectra changes are due to, respectively, sequential extrusion of blood from the topical cutaneous vascular beds and their filling afterward. The obtained results are confirmed by Monte Carlo modeling. This implies that pressure-induced influence during the human skin diffuse reflectance spectra measurements in vivo should be taken into consideration, in particular, in the rapidly developing area of wearable gadgets for real-time monitoring of various human body parameters.

Enhanced Penetration of Human Placental Tissue by SiO$_{2}$ Nanoparticles as a Result of Microneedle and Electroporation Treatments

The objective of this paper is to evaluate the penetration and accumulation of SiO $_{2}$ nanoparticles (NPs) in vitro human placental tissue as a function of NP size and electroporation (EP) and microneedle (MN) treatments. The results show that the penetration and accumulation of SiO $_{2}$ NPs has a significant influence on the optical properties. Optical coherence tomography (OCT) monitoring and diffuse reflectance (DR) spectra measurements indicate that 30 nm SiO $_{2}$ NPs have a tendency to generate greater signal intensities, while 15 nm NPs penetrated faster and had a higher penetration depth. The reduction in average attenuation coefficients of human placental tissue when the SiO $_{2}$ NPs size is constant is found to show the following trend: SiO $_{2}$ NPs in combination with EP and MN treatment $>$ SiO $_{2}$ NPs in combination with MN $>$ SiO $_{2}$ NPs with EP $>$ only SiO $_{2}$ NPs. It can be concluded that EP and MN treatments dramatically increase the penetration of SiO $_{2}$ NPs into human placental tissue. The results prove that OCT and DR spectra can be combined with EP and MN treatments to establish a theoretical basis for the safe use of SiO $_{2}$ NPs on human placental tissue and can potentially become a powerful tool for early diagnosis and monitoring of tissue diseases.