Kubelka-Munk Model Research Articles

Polymer composite cladding for selective frequency filtration: An experimental and modeling study

Laser selective frequency filtering is currently performed using expensive, heavy, and bulky (millimeters in thickness) ceramic composite claddings around the laser rod, which limits the miniaturization and transportability of the laser. The cladding absorbs undesired spontaneous emissions and reflects the desired wavelength of the "pump" diode. As an improved alternative for the cladding on, say, a diode-pumped solid-state Nd:YAG laser rod, we investigate a spray-coated polymer composite cladding (micrometers in thickness). The polymer composite cladding is easier to process and lighter and has a much smaller volume vs. traditional ceramic composite claddings. The approach is demonstrated on spray-coated glass slides, where cubic samaria (Sm2O3) particles are used as the filler in the polymer composite cladding. The rationale for using samaria as the filler in the composite is its absorption near the laser spontaneous emission wavelength (i.e., 1064 nm) and high reflectivity at the incident pump wavelength (i.e., 808 nm). The addition of a second polymer composite layer loaded with alumina particles enables reduction of the samaria composite layer thickness. The Kubelka-Munk model is shown to successfully predict the experimentally measured optical performance of single and bilayer claddings, making it a reliable design tool for multilayer claddings.

Synthesis, Characterization, Band gap calculation, DFT study and Biological implication of Two Nitrogen-rich Proligands: Polymorphic Crystal Structures and Hirshfeld surface analyses of a Thiocarbohydrazone

A novel dihydrazone proligand 1,3-bis(pyridin-4-ylmethylideneamino)guanidine hydrochloride (H3L1) is reported along with polymorphic crystal structures of an analogous proligand 1,5-bis(4-pyridinecarboxaldehyde) thiocarbohydrazone (H2L2. H2O & H2L2. 2H2O). The crystal systems of H2L2. H2O and H2L2. 2H2O are monoclinic with P21/c and C2/c space groups. Strong hydrogen bonding interactions are found to be predominate in the H2L2. 2H2O crystal lattice. Hirshfeld surface analysis reveals that, after isotropic H···H interactions, N···H and C···H interactions are found to have the highest contribution to the overall Hirshfeld surface areas of H2L2. H2O and H2L2. 2H2O respectively. The pore volume and surface area of the thiocarbohydrazone polymorphs are also calculated. Direct band gap energies for H3L1 and H2L2 in their solid-states were estimated as 2.33 and 2.58 eV respectively using the Kubelka-Munk model. Molecular geometry of both the compounds are optimised using density functional theory and quantum chemical parameters are calculated. Frontier molecular orbital energy gaps in the gas phase for H3L1 and H2L2 are found to be 4.49 and 3.55 eV respectively, which indicates strong intermolecular interaction in the solid lattice of H3L1. Absorption, distribution, metabolism and excretion (ADME) attributes indicate both compound's potential as drug candidates. In vitro antibacterial study reveals that the thiocarbohydrazone based proligand is a more efficient inhibitor against gram-positive Staphylococcus aureus bacterial species. The anticancer activities of the compounds against MCF-7 human breast cancer cells suggested that H3L1 with an IC50 value of 172.6798 µg/mL has more potent than H2L2 (IC50 value of 279.1881 µg/mL).

Exploring anticancer and antibacterial activities of two self-assembling units: Band gap calculations, DFT studies, and polymorphism of a carbohydrazone ligand

The synthesis and physicochemical characterization of a novel self-assembling unit 1,3-bis(4-hydroxyphenylmethylideneamino)guanidine hydrochloride (H5L1) and polymorphic crystal structures of an analogous proligand 1,5-bis(4-hydroxybenzaldehyde) carbohydrazone (H4L2. DMF & H4L2. H2O) are reported. The crystal systems of H4L2. DMF and H4L2. H2O are monoclinic with C2/c and P21/c space groups. The intermolecular contacts are calculated by Hirshfeld surface analyses, which reveal that H···H interactions have a maximum contribution in the total Hirshfeld surfaces in both the crystal structures. The study also signifies that hydrogen bonding interactions are dominant in the crystal lattice of H4L2. H2O, while the C–H∙∙∙π interactions are also significant in H4L2. DMF lattice. Density functional theory is used for optimizing geometry and calculating quantum chemical parameters. Theoretical frontier molecular energy gaps in the gas phase for H5L1 and H4L2 are found to be 3.49 and 4.09 eV respectively. The solid-state band gaps of H5L1 and H4L2 are determined experimentally using the Kubelka-Munk model and are found to be 2.72 and 2.43 eV respectively, which is indicative of strong intermolecular association in the solid lattice of H4L2. ADME properties are estimated to predict the drug-likeness of the compounds. In vitro antibacterial activity study reveals that the diaminoguanidine based proligand is a more efficient inhibitor against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacterial species. Also, in vitro study of the compounds against human breast cancer MCF-7 cells shows that with the increase in the concentrations of the compounds the percentage of cell viability decreases, which indicates the anticancer potentials of both compounds. The IC50 values of H5L1 and H4L2 against MCF-7 cell lines (205.62 and 247.31 µg/mL) are also found to be better compared to the same (274.59 and 375.45 µg/mL) against the non-cancerous Mouse Fibroblast (L929) cell lines.

Influence of the Mn/Fe ratio on structural, optical, electrical and magnetic characteristics of MnFeMgNiO spinel ferrites

MnxFe2-xMg0.5Ni0.5O4spinel ferrite nanoparticles (0.0 ≤ x ≤ 1) were prepared utilizing a flash auto-combustion technique. The as-prepared ferrite nanoparticles have been investigated and characterized using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared analysis (FTIR). The dielectric, optical and magnetic characteristics of the synthesized spinel ferrite samples were investigated using broadband dielectric spectroscopy (BDS), diffuse reflectance spectroscopy (DRS) and vibration sample magnetometers (VSM). The cubic phase spinel ferrite with space group Fd-3m was identified through XRD. X-ray diffraction indicates that the lattice constant increases and the crystallite size declines with increasing Mn concentration. The positions of the cations and their vibrational modes in the crystal structure with oxygen ions are demonstrated through the FTIR spectra. The morphology was examined using HRTEM showed polycrystalline cubic spinel structure with faceted planes. The optical band gap Eg was determined using Kubelka–Munk model where, it decreased from 1.79 eV to1.24 eV as Mn content increases. The replacement of manganese significantly affects the dielectric characteristics of the synthesized spinel ferrites. The real (ε′), imaginary (ε″) parts of dielectric constant and ac conductivity exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases. The presence of a relaxation phenomenon in all prepared samples except the undoped sample (Ni0.5Mg0.5Fe2O4) is shown by the imaginary modulus’s (M′′) dependence on frequency. The magnetic properties exhibited soft ferrite nature with small hysteresis curve for all spinel ferrites samples. The magnetic properties of MnxFe2-xMg0.5Ni0.5O4 nanoparticles were measured and analysed, including saturation magnetization (Ms), remanence (Mr), coercivity (Hc), and squareness ratio. (Ms), and (Mr), exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases while squareness ratio decreased. The magnetic parameters greatly affected by Mn substitution ratio.

A Novel Correction Method of Kubelka–Munk Model for Color Prediction of Pre-colored Fiber Blends

A Novel Correction Method of Kubelka–Munk Model for Color Prediction of Pre-colored Fiber Blends

The coupled WO3-AgBr nanocatalyst, part II: Synthesis, characterization, and the boosted photocatalytic activity towards metronidazole in an aqueous solution

The AgBr and WO3 nanoparticles (NPs) were synthesized and coupled, and the coupled AgBr-WO3 binary catalyst, as well as the individual AgBr and WO3 NPs, were then characterized by XRD, FTIR, DRS, and SEM-EDX. XRD results showed the formation of orthorhombic WO3 cubic AgBr crystals. The crystallite sizes of 45, 28, and 45 nm were estimated by the Scherrer formula for the as-prepared AgBr, WO3, and AgBr-WO3 catalysts, respectively. The DRS study estimated band gap energies using both absorption edge wavelengths and the Kubelka-Munk model. The band gap energies of 2.72, 3.06, and 2.92 eV were obtained for the direct electronic transitions of AgBr, WO3, and AgBr-WO3. The ECB (potential position) of AgBr and WO3 were estimated to be 0.01 and 0.52 V, while their EVB values were 2.60 and 3.55 V, respectively. Typical FTIR absorption bands of W‒OH, the W‒O‒W, and AgBr bonds have appeared at 1637 cm−1, 823 (and 766) cm−1, and 1384 cm−1, respectively. The pHpzc of 4 was estimated for the individual and coupled catalysts. In studying the photocatalytic activity of the catalysts in the photodegradation of metronidazole (MNZ) a boosted activity was achieved for the coupled system. This increased activity depends on the maximum AgBr:WO3 mole ratio in a 1:3 mol ratio. Grinding time applied to prepare the coupled catalyst has also varied the photocatalytic activity.

Copper perchlorate catalyzed oxidative cyclisation of a novel bishydrazone ligand, formation of an unusual copper complex and in vitro biological implications

A novel hexadentate bishydrazone ligand, 1,10-bis(di(2-pyridyl)ketone) adipic acid dihydrazone (H2L1) is synthesized and characterized. With copper perchlorate as a catalytic oxidant, the ligand undergoes oxidative cyclisation and resulted in the formation of an unusual copper complex [Cu(L1a)2Cl]ClO4 (1), where L1a is 3-(2-pyridyl)triazolo[1,5-a]-pyridine. The Cu(II) complex was characterized physicochemically, while the molecular structure was confirmed by single crystal X- ray diffraction. In the complex cation, copper(II) is in a distorted trigonal bipyramidal coordination environment, surrounded by two triazolo nitrogen atoms and two pyridyl nitrogen atoms of L1a and a chloride atom. The relevant non covalent intermolecular interactions of the complex quantified using Hirshfeld surface analysis reveals that the O···H/ H···O (27.2%) contacts has the highest contribution. The solution phase bandgaps of the compounds were calculated using Tauc plot, whereas the solid-state band gaps were calculated by Kubelka-Munk model. DFT studies of the compounds indicate that the theoretical calculations corroborate with the experimental data. DPPH antioxidant activity assay of the synthesized compounds showed that the proligand H2L1 has a lower IC50 value (24.1 μM) than that of complex 1 (29.7 μM). The in vitro antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus, which revealed that complex 1 have excellent activity against E. coli, much as the standard ciprofloxacin. The cytotoxic efficacy investigation of the compounds against A549 (lung) adenocarcinoma cells suggested that H2L1 has more anticancer activity (IC50 value of 149.08 μM) than that of complex 1(IC50 value of 176.70 μM).

On the validity of two-flux and four-flux models for light scattering in translucent layers: angular distribution of internally reflected light at the interfaces.

Optical characterization and appearance prediction of translucent materials are required in many fields of engineering such as computer graphics, dental restorations or 3D printing technologies. In the case of strongly scattering materials, flux transfer models like the Kubelka-Munk model (2-flux) or the Maheu's 4-flux model have been successfully used to this aim for decades. However, they lead to inaccurate prediction of the color variations of translucent objects of different thicknesses. Indeed, as they rely on the assumption of lambertian fluxes at any depth within the material, they fail to model the internal reflectance at the interfaces, penalizing the accuracy of the optical parameter extraction. The aim of this paper is to investigate the impact of translucency on light angular distribution and corresponding internal reflectances by the mean of the radiative transfer equation, which describes more rigorously the impact of scattering on light propagation. It turns out that the light angular distribution at the bordering interfaces is often far from being lambertian, and that the internal reflectance may vary significantly according to the layer's thickness, refractive index, scattering and absorption coefficients and scattering anisotropy. This work enables to better understand the impact of scattering within a translucent layer and also invites to revisit the well-known Saunderson correction used in 2- or 4-flux models.

Synthesis, structural, optical and electrical properties of CuxSbySz powders

The family of chalcogenides appears as promising candidates to act as absorbers in alternative solar cells in order to reduce the dependence on fossil fuels. The five absorber materials, CuSbS2, Cu3SbS3, Cu3SbS4, Cu12Sb4S13 and Cu14Sb4S13, were synthesized by the direct fusion of the elements inside evacuated quartz tubes. The resulting ingots were characterized electrically by the hot probe method and by direct resistance measurement. These ingots were then ground in order to obtain very fine powders. Also their pellets were characterized by X-Ray Diffraction, Raman spectroscopy, optical and electrical analysis. The X-Ray diffraction and Raman spectroscopy results confirmed the material's purity. Their band gap energies were determined by the Kubelka-Munk model, and found to be ranging between 1.24 and 1.47 eV. The five materials have P-type conductivities.

Estimation of dielectric response functions for NIR-SWIR absorbing dyes by inverse analysis of diffuse reflectance

This study describes the estimation of dielectric response functions for NIR-SWIR absorbing dyes by inverse analysis of diffuse reflectance. The inverse analysis procedure is based on the Kramers–Kronig relations, the Kubelka–Munk model of diffuse reflectance, and the background subtraction of substrate spectra. The calculated response functions provide estimates of the dielectric response characteristics for NIR-SWIR absorbing dyes, as well as their sensitivity to material-background environments. This study demonstrates that Kramers–Kronig analysis can be adopted for calculating estimates of dielectric functions, given any reasonable estimate of absorbance. Specifically, that Kramers–Kronig analysis provides filtering of dielectric response structure with respect to spectrum artifacts due to inverse-analysis and spectroscopic-measurement procedures. This can significantly reduce the experimentation necessary to achieve desired dielectric response characteristics for NIR-SWIR dye and substrate combinations. Furthermore, these calculated response functions can support the construction of approximate effective medium models capable of estimating reflectance features for dyed fabrics.

Optical properties of dental zirconia, bovine dentin, and enamel-dentin structures.

To evaluate the optical properties and the relative translucency parameter of Ceramill ZI White (3Y-TZP) and Ceramill Zolid FX White (5Y-PSZ) zirconia ceramic systems and compare them with those of the bovine dentin and enamel/dentin structures. 3Y-TZP and 5Y-PSZ zirconia ceramic systems were evaluated. A 0.5-mm-thick 3Y-TZP (3Y-NC.5), 0.5-mm-thick (5Y-NC.5), and 1.4-mm-thick (5Y-C.14) were used. A 0.5-mm-thick dentin specimens and 1.4-mm-thick enamel/dentin specimens (n = 5) were obtained from anterior bovine maxillary teeth. Scattering, absorption, transmittance, and albedo coefficient were calculated using Kubelka-Munk's model. Data were statistically analyzed using Kruskal-Wallis and Mann-Whitney tests (p < 0.001), and goodness-of-fit coefficient (GFC). Relative translucency parameter differences were evaluated using translucency thresholds. Reflectance, scattering, absorption, and transmittance properties were wavelength dependent. Good matches (GFC ≥ 0.999) in spectral reflectance were observed between 0.5-mm-thick dentin and 1.4-mm-thick enamel/dentin, and 3Y-NC.5 and 5Y-NC.5. Scattering was the main optical extinction process during light interaction with zirconia and dental structures, as indicated by albedo coefficient. Translucency differences were acceptable only for 3Y-NC.5 and the dentin structure, and 5Y-C.14 and the enamel/dentin structure. Optical properties of 3Y-TZP and 5Y-PSZ dental zirconia differed from each other and from bovine dental structures. Nevertheless, 3Y-TZP showed similar relative translucency parameter to bovine dentin. To achieve the best esthetic results in restorative dentistry, it is crucial for clinicians to know about the optical properties of 3Y-TZP and 5Y-PSZ and to be able to compare these properties with those of dental structures.

Crystal structure reinvestigation and spectroscopic analysis of tricadmium orthophosphate.

Single crystals of tricadmium orthophosphate, Cd3(PO4)2, have been synthesized successfully by the hydro-thermal route, while its powder form was obtained by a solid-solid process. The corresponding crystal structure was determined using X-ray diffraction data in the monoclinic space group P21/n. The crystal structure consists of Cd2O8 or Cd2O10 dimers linked together by PO4 tetra-hedra through sharing vertices or edges. Scanning electron microscopy (SEM) was used to investigate the morphology and to confirm the chemical composition of the synthesized powder. Infrared analysis corroborates the presence of isolated phosphate tetra-hedrons in the structure. UV-Visible studies showed an absorbance peak at 289 nm and a band gap energy of 3.85 eV, as determined by the Kubelka-Munk model.

Spectral, band gap and DFT studies of novel cobalt (II) complexes of N(4)-cyclohexylthiosemicarbazones: Molecular docking with DNA and SARS-CoV-2 Mpro

The synthesis and characterization of four novel cobalt complexes CoL12 (1), [Co(HL2)L2]Cl (2), CoL22 (3) and [Co(HL2)L2]Br (4) of thiosemicarbazones HL1 and HL2, (where HL1 is 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone and HL2 is quinoline-2-carbaldehyde-N(4)-cyclohexylthiosemicarbazone) are reported. The new ligand HL2 was characterized physicochemically and the structure was confirmed by single crystal X-ray diffraction technique. The relevant intermolecular interactions of HL2 were quantified using Hirshfeld surface analysis. The coordination of the Schiff bases to the metal ions were assigned with the help of physicochemical methods, which indicate octahedral geometry for all the complexes. The deprotonated ligands coordinate via pyridinyl nitrogen, azomethine nitrogen and thiolate sulfur atoms in all the complexes. However, the NNS coordination of the neutral thione ligand is also present in the complexes 2 and 4. Furthermore, geometrical optimization and theoretical calculations of the compounds were achieved by density functional theory quantum chemical computational methods. The direct bandgaps of the complexes were calculated experimentally using the Kubelka-Munk model, which shows a range of 1.62–2.09 eV and corroborates with the theoretical studies. In silico molecular docking studies of all the compounds were performed with B-DNA dodecamer and are all indicative of groove mode of binding. All the compounds exhibit strong putative binding potentials toward duplex DNA. Interestingly, the putative binding efficiency of the complexes 1 and 3 with SARS-CoV-2 main protease is also found very higher compared to the repurposed drugs that are specifically active at 6Y2F.

Optical behavior of 3D-printed dental restorative resins: Influence of thickness and printing angle.

To evaluate the influence of thickness and printing angle on the optical properties of 3D-printed dental restorative resins. Four 3D printing resin systems were evaluated: DFT-Detax Freeprint Temp; FP- Formlabs Permanent Crown; FP- Formlabs Temporary CB; and GCT- GC Temporary-. Samples from each material were printed at 0° and 90°, and polished up to 0.5, 1.0, 1.5 and 2.0mm thickness. Scattering (S), absorption (K) and albedo (a) coefficients, transmittance (T%), light reflectivity (RI) and infinite optical thickness (X∞) were calculated using Kubelka-Munk's model. Data were statistically analyzed using Kruskal-Wallis¸ Mann-Whitney tests, and VAF coefficient. The spectral distribution on S, K, T%, RI,X∞ were wavelength dependent. Although the spectral behaviors were similar for all the specimens evaluated, the values of S, K, T% andX∞ presented significant differences between specimen thicknesses for all the materials used and for both printing orientations. Values for S and K increased, and T% and X∞ decreased. Significant differences between 0° and 90° were found for RI values at 0.5 and 1.0 mm thick samples, for S and K at 2.0 mm, for X∞ at 0.5 and 1.0 mm for DFT, and at 0.5 mm for FT. Optical properties of 3D-printed restorative resins vary between thicknesses, and could be affected by the building orientation. Therefore, these factors should be considered in order to improve the biomimetic potential of 3D-printed dental restorative resins. Understanding the optical behavior of the 3D-printed restorative resins is essential to optimize their clinical performance.

Positive and Negative Photoconductivity in Ir Nanofilm-Coated MoO3 Bias-Switching Photodetector.

In this study, we delved into the influence of Ir nanofilm coating thickness on the optical and optoelectronic behavior of ultrathin MoO3 wafer-scale devices. Notably, the 4 nm Ir coating showed a negative Hall voltage and high carrier concentration of 1.524 × 1019 cm-3 with 0.19 nm roughness. Using the Kubelka-Munk model, we found that the bandgap decreased with increasing Ir thickness, consistent with Urbach tail energy suggesting a lower level of disorder. Regarding transient photocurrent behavior, all samples exhibited high stability under both dark and UV conditions. We also observed a positive photoconductivity at bias voltages of >0.5 V, while at 0 V bias voltage, the samples displayed a negative photoconductivity behavior. This unique aspect allowed us to explore self-powered negative photodetectors, showcasing fast response and recovery times of 0.36/0.42 s at 0 V. The intriguing negative photoresponse that we observed is linked to hole self-trapping/charge exciton and Joule heating effects.

An experimental design study of photocatalytic activity of the Z-scheme silver iodide/tungstate binary nano photocatalyst.

A binary AgI/ Ag2WO4 photocatalyst was fabricated and characterized by SEM, XRD, UV-Vis DRS, and FT-IR. It was then used to photodegrade sodium ceftriaxone (CTX) in an aqueous solution. The band gap energies of 2.95, 2.78, and 2.62eV were obtained by the Kubelka-Munk model for Ag2WO4, AgI, and AgI/Ag2WO4 catalysts. The samples have pHPZC values of 6.9, 4.2, and 6.6, respectively. The synergistic photocatalytic activity of the coupled system depended on the AgI:Ag2WO4 mole ratio and grinding time (optimums:mole ratio of 4:1 and time 30min). The experimental design was used for optimizing the conditions and a quadratic model well-processed the data based on the model F value of 131.87 > F0.05,14,13 = 2.55 and LOF F value of 0.78 < F0.05,10,3 = 8.78. The optimized RSM run included the irradiation time of 85min, 3.5mg/L of CTX sample at pH 9, and a catalyst dose of 1.0g/L. Under the optimized conditions, about 63% of CTX molecules were photodegraded. In the study of the scavenging agents, the direct Z-scheme mechanism accumulated electrons in the CB-AgI and the holes in the VB-Ag2WO4 level, as stronger reducing and oxidizing centers than the accumulated electrons and holes of the type (II) heterojunction mechanism. Compared to a CTX oxidation potential of about 0.06V, the direct Z-scheme mechanism is more favorable to reduce or oxidize it.

Translucent multi-layered zirconia: Sandblasting effect on optical and mechanical properties.

The aim of this study was to evaluate the influence of the sandblasting treatment on the microstructure, optical and mechanical properties of multi-layered translucent zirconia. Samples of yttria-stabilized zirconia were prepared by stratifying four layers (L1, L2, L3 and L4) of ML-type KATANA multi-layered monolithic discs, whose surfaces were then sandblasted with alumina particles (110µm and 0.2MPa) in order to evaluate its effect on the presence of different crystalline phases as well as on the optical and mechanical properties of each of the four layers. The optical characterization was carried out by measuring the reflectance spectrum and colorimetric parameters by UV-Vis spectrophotometric analysis and the transmittance curves were indirectly obtained using the Kubelka-Munk model (KM). Microstructural, structural, mechanical and roughness characterizations were also performed using SEM, XRD, biaxial flexural strength B3B, and light interferometry, respectively RESULTS: According to the KM model there are different degrees of translucency between the upper and lower layers of the monolithic discs, but there was no influence of the Al2O3-sandblasting treatment on this optical property. The disk pigmentation causes greater absorption of light below 600nm, decreasing the transmittance rate to values below 25% in this region of the spectrum. The yellowing index presented higher values for inner disk layers L3 and L4, in agreement with the highest values of the light absorption coefficient K observed for these layers. The roughness of the samples did not change significantly with the surface treatment performed and the sandblasting did not result in new crystalline phases. SEM analysis showed the presence of different grain sizes in all layers analyzed, being related to the co-occurring presence of cubic (c-ZrO2) and tetragonal (t-ZrO2) phases in similar contents (∼ 50wt%). The Weibull statistical analysis, in turn, showed an increase in the Weibull characteristic stress value (σ0) for most layers subjected to sandblasting, except for the second layer (central region of the disk). It was also verified an increase in the value of the structural reliability of the material (m), referring to the samples of the central region of the disc (L2 and L3 layers) after sandblasting. The pigmentation in the disk causes a decrease of the transmittance rate to values well below 25% in the region of the spectrum 400-600nm and the inner layers (L3 and L4) have even lower transmittance than the outer layers in this spectrum range. Although the CR index indicates variation related to the Al2O3-sandblasting treatment, the transmittance spectra of KM model show that the sandblasting did not cause a significant change in the transmittance rate of the four analyzed layers. Also, there is no significant difference in the light scattering of the different layers of the disc, either before or after Al2O3-sandblasting treatment.

Solvothermal self-assembly of a novel metal-organic square grid complex using a biscarbohydrazone ligand building block: Crystal structures, Hirshfeld and void surface analyses, band gap calculations and DFT studies

Here we report the solvothermal self-assembly of a novel metal–organic square complex [Zn(HL)]4Cl2·ZnCl4·16H2O (1) using 1,5-bis(2-benzoylpyridine) carbohydrazone (H2L) ligand building block. Single-crystal X-ray diffraction (SCXRD) study confirm the structure of the complex, which is characterized by other physicochemical methods. The crystal study reveals the presence of a tetrahedral ZnCl42- counter anion also. The DFT quantum chemical calculations and analysis of the square grid cation are explored first time and are compared with the crystal structure and DFT calculations of the ligand building block H2L also. The solid-state band gap (Eg) of the ligand and the square grid complex are determined experimentally using the Kubelka-Munk model and are found to be 3.22 and 1.74 eV respectively. Hirshfeld surface (HS) analyses of both the building block and the complex were also explored to quantify the intermolecular interactions in their crystal lattices. The molecular packing of the complex and the ligand were found to be dominated by isotropic H···H contacts. However, strong H···Cl contacts are contributing the most in the crystal structure cohesion of the complex, while the C···H interactions are the dominating anisotropic forces contributing to the overall Hirshfeld surface in the ligand lattice. The theoretical void space calculations of the complex [Zn(HL)]4Cl2·ZnCl4 (1a) were then carried out. The close packing in the crystal lattice possesses small voids and cavities and an isosurface value of 0.0008 au was found suitable for crystal void calculation, in agreement with PLATON calculations. The corresponding pore volume and the surface area per unit cell were found to be 940.58 Å3 and 1656.04 Å2 respectively.

Ex Vivo Optical Properties Estimation for Reliable Tissue Characterization

: Lasers are demonstrating high impact in many medical and biological applications. They have different interaction mechanisms within tissues depending on operational parameters, particularly the wavelength. In addition, the optical properties of the examined tissue (i.e., absorption and scattering properties) influence the efficacy of the applied laser. The development of optical biomedical techniques relies on the examination of tissues’ optical properties, which describe the viability of tissue optical evaluation and the effect of light on the tissue. Understanding the optical properties of tissues is necessary for the interpretation and evaluation of diagnostic data, as well as the prediction of light and energy absorption for therapeutic and surgical applications. Moreover, the accuracy of many applications, including tissue removal and coagulation, depends on the tissues' spectroscopic characteristics. In the current paper, a set of ex vivo absorption and scattering coefficients of different types of biological samples (skin, skull, liver and muscle) at 650 nm laser irradiation were retrieved using an integrating phere system paired with the Kubelka–Munk model. The obtained optical parameters were utilized to acquire the local fluence rate within the irradiated tissues based on the Monte Carlo simulation method and the diffusion approximation of the radiative transfer equation. The obtained results reveal that the optical absorption and scattering coefficients control the light propagation and distribution within biological tissues. Such an understanding refers to system design optimization, light delivery accuracy and the minimization of undesirable physiological effects such as phototoxicity or photobleaching.

UV excitable GdSr2AlO5:Eu3+ red emitting nanophosphors: Structure refinement, photoluminescence, Judd-Ofelt analysis and thermal stability for w-LEDs

Combustion derived Gd1−xSr2AlO5:x mol% Eu3+(x = 1–5 mol%) nanophosphors have tetragonal structure with space-symmetry of I4/mcm (space group no. 140), which was supported by X-ray diffraction patterns. Rietveld refinement pattern revealed that the doping of Eu3+ ions expanded the lattice constants/volume and shifted the diffraction peaks to a lower angle side. Investigations using SEM and TEM confirm the excellent morphology with almost spherical particles in nanoscale. The production of material with the proper stoichiometry was confirmed by EDX analysis. Optical band-gap value (5.21 eV) of optimum Gd0.97Sr2AlO5:3 mol% Eu3+ which was determined by Kubelka-Munk model, showed the good optical quality of the samples. At 268 nm excitation wavelengths, PL spectra characteristics show a strong red emission at 612 nm that corresponds to the doped Eu3+ ions hypersensitive 5D0→7F2 transition with good asymmetric ratio. The optimal doping concentration of Eu3+ ions in GdSr2AlO5 is determined to be about 3 mol% and the concentration quenching phenomenon arise from the electric dipole-quadrupole interaction. Additionally, the Judd-Ofelt investigation of GdSr2AlO5:Eu3+ phosphors were intended to determine the coordinated Eu3+ environment inside the host matrix. The experimental life time analysis of the excited state 5D0 was determined to be in the millisecond range and the quantum efficiency for optimum sample was found to be 67.62 % yielding a good white light emission. The temperature dependent luminescence behavior of Gd0.97Sr2AlO5:3 mol% Eu3+ phosphor exhibits its good thermal stability and the activation energy for thermal quenching characteristics is calculated to be 0.216 eV. The potential applicability of GdSr2AlO5:Eu3+ nanophosphor in the production of wLEDs was further improved by the color coordinates.