Optical Absorption Measurements Research Articles

Facile one-pot synthesis and characterization of ZnSe/HPMC nanocomposites

Herein, we report the facile synthesis of ZnSe/HPMC (Hydroxypropyl Methyl Cellulose) nanocomposites by in-situ method. The biodegradable HPMC polymer acts as capping molecule as well as polymer matrix. The optical and structural properties of ZnSe/HPMC nanocomposites were studied by optical absorption, photoluminescence (PL) spectroscopy, FTIR, XRD and TEM measurements. Size of the ZnSe nanoparticles was tuned by controlling the pH of the reaction. As prepared ZnSe nanoparticles were spherical in shape, homogeneously distributed in the polymer and XRD patterns exhibit face centred cubic phase. The present method is a novel approach for the synthesis of ZnSe nanoparticles using HPMC as a capping molecule as well as matrix to develop nanocomposite.

Self‐Assembly of MnS Shell on CdTe Nanoparticles Induced by Thermohydrolysis: Synthesis and Characterization

Herein, CdTe/MnS core/shell nanoparticles dispersed in an aqueous solution have been synthesized. The formation of MnS semiconductor shell occurs by spontaneous self‐assembly. This process is activated by thermal hydrolysis that removes the excess of thiol and releases S2− ions. In this process, Mn2+ ions on the surface of the CdTe nanoparticles bind to S2− ions to produce a fine semiconducting layer of MnS. Measurements of Raman spectroscopy, optical absorption, and electrochemical measurements are performed. The Raman spectrum shows CdTe characteristic bands at 141 and 163 cm−1. Bands at 221 and 444 cm−1 are associated with the MnS structure. Cyclic voltammetry and differential pulse voltammetry are used to estimate the electrochemical gap at ≈2.47 eV. Absorption optical measurements show tree absorption bands. A broad band between 460 and 520 nm is associated with the first transition in CdTe nanoparticle. The absorption spectrum reveals an optical gap in the range of 2.41–2.33 eV for all the refluxed samples. These values are consistent with those obtained with the electrochemical measurements. The results evidence the formation of a core–shell semiconducting nanostructure made of CdTe nanoparticles coated with a spontaneously self‐assembled thin layer of MnS nanoparticles.

New lead-freeIodoantimonatehalide semiconductor: Synthesis, Structural characterization, DFT calculations, Hirshfeld surface, Thermal behavior, vibrational and optical properties

Hybrid metal halides have captured broad interest in the lighting and display fields because of their unique electronic structures and splendid broadband emission properties. Organic chiral building blocks can control light, charge, and spin interconversion in hybrid crystalline semiconductors with metal-halide.Based on the chiral organic molecules(S)-1-phenylethylamine, we synthesized new chiral antimony halidewith zero-dimensional structure((S)-C8H12N)4Sb2I10. Atroom temperature, the title compound is crystallized in the monoclinic P21with Z = 2 and the following unit cell dimensions: a = 12.69129 (15) Å, b = 14.96770 (15) Å, c =13.91397 (16) Å, and β = 92.2735 (11)°.The crystal structure of this compound is composed of two crystallographically independent [Sb2I10]4- unit and four (S)-1-phenylethylammonium per unit cell. The crystal packing is governed by N-H....I hydrogen bonds.Intermolecular interactions seen in the grown single crystal are studied by Hirshfeld surface and 2-D fingerprint plot.In addition to study the weak interaction a visualized approach known as RDG has been carried out.The recorded infrared IR and Raman studies confirm vibrational modes for organic and inorganic groups at room temperature in the 500-4000 cm−1 and 50-4000 cm−1 frequency regions, respectively.The optimized molecular structure and vibrational frequencies were calculated by the Density Functional Theory (DFT) method using the B3LYP level employing a LANL2DZbasis set.The title compound reveals thermal stability up to 190°C.The opticalabsorption measurement confirms the semiconductor nature with a band gap of around 3.74 eV. The frontier molecular orbital analysis HOMO-LUMOof molecule were studied.

Self-assembled tin(IV) organic-inorganic hybrids: Synthesis, spectral, structural, and Hirshfeld surface analysis of bis(thiomorpholinium) hexahalostannate(IV)

At room temperature, organic-inorganic hybrids, including bis(thiomorpholinium) hexachlorostannate(IV) hydrate (1) and bis(thiomorpholinium) hexabromostannate(IV) (2), were synthesized from thiomorpholinium chloride/bromide. The hybrids underwent characterization using, IR, elemental, NMR, TGA, DRS and PL spectroscopy, along with single-crystal X-ray diffraction (SCXRD). SCXRD confirms compounds are crystallized in a monoclinic system exhibiting centrosymmetric space groups (C2/candP21/c for (1) and (2)). The SCXRD structures of the hybrids unveiled significant H-bonded interactions between the thiomorpholinium cation and the SnCl62-/SnBr62- anions. At room temperature, optical absorption measurements revealed band gaps of 3.91 eV for (1) and 3.00 eV for (2).TGA confirmed the proposed formulas of the compounds.BVS calculations conducted on SnCl62- and SnBr62- anions yielded values of 4.01 and 3.94, respectively. Fingerprint plots were employed to identify and quantify the proportion of hydrogen bonding interactions.

Temperature dependence of the near infrared absorption spectrum of single-wall carbon nanotubes dispersed by sodium dodecyl sulfate in aqueous solution: experiments and molecular dynamics study.

Single-wall carbon nanotubes (SWCNT) dispersed in water with the help of sodium dodecyl sulfate (SDS) surfactants exhibit a temperature dependent near infrared (NIR) exciton spectrum. Due to their biocompatibility and NIR spectrum falling within the transparent window for biological tissue, SWCNTs hold potential for sensing temperature inside cells. Here, we seek to elucidate the mechanism responsible for this temperature dependence, focusing on changes in the water coverage of the SWCNT as the surfactant structure changes with temperature. We compare optical absorption spectra in the UV-Vis-IR range and fully atomistic molecular dynamics (MD) simulations. The observed temperature dependence of the spectra for various SWCNTs may be attributed to changes in the dielectric environment and its impact on excitons. MD simulations reveal that the adsorbed SDS molecules effectively shield the SWCNT, with ~ 70% of water molecules removed from the first two adlayers; this coverage shows a modest temperature dependence. Although we are not able to directly demonstrate how this influences the NIR spectrum, this represents a potential pathway given the strong influence of the water environment on the excitons in SWCNTs. Optical absorption measurements were carried out in the UV-Vis-NIR range using a Varian Cary 5000 spectrophotometer in a temperature-controlled environment. PeakFit™ v. 4.06 was used as peak-fitting program in the spectral range 900-1400nm (890-1380meV) as a function of the temperature. Fully atomistic molecular dynamics simulations were conducted using the NAMD2 package. The CHARMM force field comprising two-body bond stretching, three-body angle deformation, four-body dihedral angle deformation, and nonbonded interactions (electrostatic and Lennard-Jones 6-16 potentials) was employed.

Exploring the structural, optical and photoluminescence of novel terbium-doped barium borosilicate glasses for high-performance technologies

The production process involved the use of the melt-quenching approach to produce a series of barium borosilicate glasses with the specific chemical formula 55B2O3+(26-x)BaO+12SiO2+7Na2O + xTb4O7, where x = 0, 0.5, 1, 2, and 3 mol%. X-ray diffraction (XRD), Raman spectroscopy, optical absorption, and photoluminescence spectra measurement were used to examine the prepared samples. X-ray diffraction revealed the non-crystalline character of the assembled samples. The Raman spectroscopy revealed that the incorporation of Tb4O7 into borosilicate glasses induced alterations in their structure. As the doping of Tb3+ ions increases, the density and molar volume of the glasses under investigation increase. Furthermore, the ion concentration and field strength increase while the polaron radius and inter-ionic distance decrease. The glass optical absorption spectra showed five peaks in the wavelength range from 300 nm to 2000 nm: 5L10, 5D3, 5D4, 7F(0, 1, 2), and 7F3, attributed to Tb3+ ion electronic transitions. In addition, optical parameters like optical energy gap, Urbach energy, refractive index, molar refractive index, reflection loss, electronic polarizability, and optical transmission coefficient were computed. Terbium-doped borosilicate glasses had a decreased optical energy gap and an improved refractive index. Photoluminescence spectra were excited at 325 nm and showed five peaks in the range of 400–750 nm. Photoluminescence (PL) emission spectra exhibit distinct peaks in the visible range.

Impact of electronic correlation on strong laser-induced bound-state transitions

Electron correlation (EC) plays a crucial role in all multi-electron systems and dynamic processes. In this work, we focus on strong laser-induced bound-bound transitions (BBT), which are fundamental to optical absorption measurements. We use the helium atom, the simplest two-electron system, as our test case, utilizing the ab initio code package HeTDSE. We examined the bound state energy levels, transition dipole moments (TDMs), and the dynamics of strong laser-induced BBT, both with and without considering EC. Our results indicate that EC significantly impacts the energy levels of the bound states and the TDMs. These effects collectively influence the transition dynamics of the excited states. Although EC does not alter the quantum transition pathways between resonance states, it generally increases the probability of resonance transitions in most cases. Our findings provide a quantitative description of EC in laser-induced BBT.

3D Lead-Organoselenide-Halide Perovskites and their Mixed-Chalcogenide and Mixed-Halide Alloys.

We incorporate Se into the 3D halide perovskite framework using the zwitterionic ligand: SeCYS (+NH3(CH2)2Se-), which occupies both the X- and A+ sites in the prototypical ABX3 perovskite. The new organoselenide-halide perovskites: (SeCYS)PbX2 (X = Cl, Br) expand upon the recently discovered organosulfide-halide perovskites. Single-crystal X-ray diffraction and pair distribution function analysis reveal the average structures of the organoselenide-halide perovskites, whereas the local lead coordination environments and their distributions were probed through solid-state 77Se and 207Pb NMR, complemented by theoretical simulations. Density functional theory calculations illustrate that the band structures of (SeCYS)PbX2 largely resemble those of their S analogs, with similar band dispersion patterns, yet with a considerable bandgap decrease. Optical absorbance measurements indeed show bandgaps of 2.07 and 1.86 eV for (SeCYS)PbX2 with X = Cl and Br, respectively. We further demonstrate routes to alloying the halides (Cl, Br) and chalcogenides (S, Se) continuously tuning the bandgap from 1.86 to 2.31 eV-straddling the ideal range for tandem solar cells or visible-light photocatalysis. The comprehensive description of the average and local structures, and how they can fine-tune the bandgap and potential trap states, respectively, establishes the foundation for understanding this new perovskite family, which combines solid-state and organo-main-group chemistry.

3D Lead‐Organoselenide‐Halide Perovskites and their Mixed‐Chalcogenide and Mixed‐Halide Alloys

We incorporate Se into the 3D halide perovskite framework using the zwitterionic ligand: SeCYS (+NH3(CH2)2Se−), which occupies both the X− and A+ sites in the prototypical ABX3 perovskite. The new organoselenide‐halide perovskites: (SeCYS)PbX2 (X = Cl, Br) expand upon the recently discovered organosulfide‐halide perovskites. Single‐crystal X‐ray diffraction and pair distribution function analysis reveal the average structures of the organoselenide‐halide perovskites, whereas the local lead coordination environments and their distributions were probed through solid‐state 77Se and 207Pb NMR, complemented by theoretical simulations. Density functional theory calculations illustrate that the band structures of (SeCYS)PbX2 largely resemble those of their S analogs, with similar band dispersion patterns, yet with a considerable bandgap decrease. Optical absorbance measurements indeed show bandgaps of 2.07 and 1.86 eV for (SeCYS)PbX2 with X = Cl and Br, respectively. We further demonstrate routes to alloying the halides (Cl, Br) and chalcogenides (S, Se) continuously tuning the bandgap from 1.86 to 2.31 eV—straddling the ideal range for tandem solar cells or visible‐light photocatalysis. The comprehensive description of the average and local structures, and how they can fine‐tune the bandgap and potential trap states, respectively, establishes the foundation for understanding this new perovskite family, which combines solid‐state and organo‐main‐group chemistry.

Structural, optical, and electrical properties of multi-component P-type oxide-semiconductor Cu-Mn-Sn-O thin films

P-type oxide semiconductors have attracted significant attention as conducting channel layers due to their wide applications in electronic devices. In this study, multi-component oxide-semiconductor Cu1–2xMnxSnxO thin films with x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, and 0.33 were prepared on glass substrates using a solution process accompanied by a spin-coating technique. A phase transition between the cupric oxide monoclinic structure and the rock salt structure was observed with increasing concentrations of Mn and Sn, while the concentration of Cu simultaneously decreased in the precursors. The crystallite size decreased throughout the samples, reaching a minimum value of 9.8 nm at an equimolar ratio. Scanning electron microscopy further confirmed this downward trend and indicated an improvement in the quality of the film surfaces. According to the optical absorption measurements, the bandgap energy ranged from 2.68 to 3.44 eV. Interestingly, the sheet resistance of Cu1–2xMnxSnxO films dropped sharply from 5.24 kΩ/sq for CuO to 0.034 kΩ/sq for the film with a molar ratio of Cu:Mn:Sn being 34:33:33.

Electronic states near surfaces and interfaces of β-Ga2O3 and κ-Ga2O3 epilayers investigated by surface photovoltage spectroscopy, photoconductivity and optical absorption

Transient surface photovoltage (SPV) spectroscopy, optical absorption, and photoconductivity (PC) were applied to study electronic transitions in (-201) β-Ga2O3 and (001) κ-Ga2O3 epitaxial layers on c-plane sapphire substrates. SPV signals were distinguished for charge separation near the surface and near the layer/substrate interface. The bandgaps of β-Ga2O3 and κ-Ga2O3 epitaxial layers were found to be, respectively, about 4.75 and 4.79 eV from optical absorption measurements, about 4.8 and 4.9 eV from PC, and 4.65 and 4.9 (near the surface) from SPV measurements. Near the κ-Ga2O3 layer/substrate interface SPV instead gives a value of 4.75 eV, possibly related to the presence of an interlayer. Defect-related transitions with onset energies at about 4.5, 4.1, and 3.5 eV were observed along the whole β-Ga2O3 layer cross-section. In contrast, defects related to different transitions were differently distributed in κ-Ga2O3 epitaxial layers: transitions setting on at about 4.3 eV originate from defects uniformly distributed across the layer, while transitions starting at 2.4 eV and 1.7 eV were respectively connected with defects located near the surface or near the layer/substrate interface. The PC measurements at photo-excitation energy above the bandgap indicated that defect densities and recombination losses were much larger in κ-Ga2O3 than in β-Ga2O3.

Structural, optical and thermoluminescence properties of amazonite

This study presents an analysis of the structural and thermoluminescence properties of amazonite, a feldspar species. The characterization was done using X-ray diffraction (XRD), X-ray fluorescence (XRF), optical spectroscopy, and vibrational spectroscopies such as Raman and Fourier Transform Infrared (FTIR). The sample exhibits a partial (Al, Si) ordenation, and contains an albite phase in addition to microcline. FTIR and Raman indicated the presence of water and OH– vibration modes. Optical absorption measurements highlighted the influence of the hydroxyl groups as catalyst for Pb transitions, contributing to the coloration of amazonite. Thermoluminescence (TL) studies were performed within a dose range from 0.1 to 10 Gy using a built-in beta source (90Sr/90Y; delivering 10 mGy/s), showing seven TL glow peaks based on non-first kinetic order. The sample exhibited a linear dose–response, with TL signals proving to be both repeatable and reproducible (CV ∼ 2%). Fading analysis showed the first two TL peaks disappear after 16 days of dark storage. Thermal quenching behavior was investigated under various heating rates, demonstrating a decrease in luminescence efficiency with increasing heating rates. Additionally, the activation energies were determined using different methods, and the amazonite TL glow curve presented activation energies values within 0.7 to 2 eV.

2D hybrid organic-inorganic perovskite displaying narrow-band violet-blue photoluminescence

Hybrid organic-inorganic perovskites represent a drastically expanding class of solid-state semiconducting materials for optoelectronics and photovoltaics. Thanks to the easy chemical tunability, this class of materials can offer emitters of very wide spectral range, however, violet-blue emitting hybrid perovskites still remain underrepresented. In this paper we report on a novel two-dimensional hybrid organic-inorganic perovskite (ethylammonium)2CdBr4. Crystal structure of the reported compound is composed of infinite inorganic 2D layers that are created by [CdBr6]4- octahedra connected in corner-by-corner manner. These layers are separated by organic ethyammonium cations which create hydrogen bonds with the inorganic part. Optical absorption measurements revealed the presence of a large band gap of 4.25 eV. Importantly, this material displays narrow photoluminescence band at 388 nm (full width at half maximum is 32 nm). Chromaticity coordinates of the perovskite emission are close to NTSC blue standard. Band structure and DOS calculations show that the states close to Fermi level predominantly originate from cadmium and bromide. Thus, here we offer a facile way towards violet-blue luminophore containing simple and widely available organic cation ethylammonium.

Synthesis of ZnO and CuO–ZnO nanocomposites for photo-conducting and dielectric applications

Zinc oxide (ZnO) and its composites has garnered a tremendous attention lately due to its effective role in electronic and optoelectronic applications. The present manuscript reports the synthesis and characterization of ZnO and CuO–ZnO nanocomposites. These samples were synthesized using precipitation technique and studied for voltage-dependent dielectrics and photoconductivity properties. Structural properties were thoroughly investigated using powder X-ray diffraction (PXRD) measurements. The composite material revealed decreased crystallinity and increased strain in the material. Optical absorption measurements were recorded using UV–vis diffusion reflectance measurements and the changes in the absorbance spectrum corresponding bandgap is explored. The obtained band gap is comparatively less for the composite material when compared with prestine ZnO. Structural morphology of the synthesized materials was observed and compared and changes in the composites when compared with the ZnO. Drastic changes in the morphology is witnessed. Electrical response of these synthesized semiconductors was studied using I–V and dielectric measurements. CuO–ZnO samples show a very clear sensitivity to the voltage dependent dielectric properties compared to ZnO. The composite and ZnO are studied using I–V measurements and the light dependent I–V measurements and composite revealed photo sensitivity. Drastic change in the conductivity is witnessed inferring the material to be used in optoelectronic application. Dielectric, Impedance, dielectric loss, AC conductivity and modulus index of the materials were explored by subjecting the materials to impedance measurements. The materials were also explored with different voltages and compared. The composite material revealed drastic variations for change in the voltage and measured parameters were compared with the ZnO.

Optoelectronic properties of β-Cyclodextrin compound and doped with Na: Comparative study by experimental and DFT approaches

The chemical and physical properties of β-Cyclodextrin (β-CD) and doped with Na can be useful in drug delivery, organic solar cells and photoprotective applications. Physicochemical properties of pure β-CD and doped with Na were investigated by both density functional theory (DFT) and experimental methods. Theoretical calculations and the experimental measurements revealed that β-CD has a direct band gap of 3.44 and 4.14 eV, respectively. The optical absorption measurements indicate that band gap value decreases by Na doping to 3.09 eV. DOS spectra confirmed the stabilization of β-CD by the strong covalent bonds between C and O atoms. Obtained small effective mass of charge carriers with the high carrier mobility in β-CD show that it is a good candidate for using in the organic electronic applications. The significant isotropic behavior was observed in all optical spectra. The positive values of the real part of dielectric function confirm the dielectric nature of β-CD. Maximum dielectric polarization is observed at the ultraviolet region with the static dielectric constant of 2.03. High reflectivity at the ultraviolet region and beyond that confirm the photoprotective properties of β-CD compound against harmful solar radiations. There is a good agreement between the obtained experimental and DFT spectra. Our findings may be useful in design of new organic optoelectronic devices.

Mg/S@g-C3N4 nanosheets: A promising fluorescence sensor for selective Cu2+ detection in water

This work describes the development of a novel fluorescence sensor based on magnesium/S@g-C3N4 nanosheets for selective detection of copper (Cu2+) ions in water. Mg/S@g-C3N4 nanosheets were prepared by the polycondensation technique and investigated by X-ray diffraction (XRD), ATR-FTIR spectroscopy, scanning electron microscopy (SEM), surface area (BET), and UV–Vis optical absorption measurements. XRD and ATR-FTIR analysis showed the characteristic peaks for S@g-C3N4. The broad full width at half maximum (0.056 radians) implies a smaller crystallite size, representing smaller Mg/S@g-C3N4 sheets. SEM micrograph showed non-exfoliated nanosheets with flake-like structures. The EDS mapping confirmed the presence of magnesium, carbon, nitrogen, and sulfur throughout the nanosheets. The Mg/S@g-C3N4 nanosheets possess a high surface area of 40 m2/g and mesopores within the nanosheets, with a size of 1.57 nm. The band gap of the Mg/S@g-C3N4 nanosheet was estimated to be 3.0 eV. The sensor exhibits a strong quenching response towards Cu2+ ions, with a decrease in fluorescence intensity as the concentration of Cu2+ increased from 1 μM to 20 μM. The Stern-Volmer quenching constant (KSV) showed a relatively high value of 185053 M−1. The estimated value of LOD by the Mg/S@g-C3N4 sensor for Cu2+ was 16.2 nM. The sensor offered high sensitivity and selectivity for Cu2+ detection over other heavy metals.

Phase‐Controlled Synthesis of Large‐Area Trigonal 2D Cr2S3 Thin Films via Ultralow Gas‐Flow Governed Dynamic Transport

AbstractAs for nonlayered 2D polymorphic materials, especially for Cr‐based chalcogenides, large‐area thin film growth with phase control is considered the most important synthesis challenge for magnetic, electronic, and optoelectronic devices. However, the synthesis methods of large continuous thin films for nonlayered 2D materials are still limited and rarely reported, also for the phase control growth, which is inhibited by isotropic 3D growth and similar Gibbs free energy for different phases. Herein, enhanced mass transport chemical vapor deposition is established to achieve the control synthesis of trigonal Cr2S3 thin films, in which the stable boundary layer supplies the continuous reaction species and tunes the reaction kinetics. The trigonal phase formation is confirmed by atomic structure characterization, optical absorption and piezoelectric measurements, demonstrating unique physical properties different from rhombohedral phase. The trigonal Cr2S3 thin films show obvious layer independent and dissimilar angle‐resolved harmonic generation, indicating the surface broken symmetry that can be understood by the combination of negligible piezoelectric response for bulk. The work presents the large‐area synthesized strategy by the modification of mass transport for nonlayered 2D materials with new phase formation and establishes the surface symmetry breaking dominated SHG mechanism for future nonlinear optical materials.

A polymerase chain reaction experiment using Escherichia coli and Mars sand simulant for detection and analysis of extraterrestrial life

In this study, we conducted polymerase chain reaction (PCR) experiments using Escherichia coli (E. coli) and a Mars sand simulant (Mars Global Simulant MGS-1, Exolith Lab) to detect and analyze potential extraterrestrial life. The targeted DNA sequence is common among the bacterial kingdom on Earth. PCR experiments conducted after alkaline heat extraction, wherein samples with varying amounts of Mars sand simulant were compared, revealed that the simulant interfered with DNA detection. We then conducted PCR experiments following treatment with a sand DNA extraction kit on samples with various E. coli densities. DNA bands for a minimum E. coli density of 900 cells/(g sand) were confirmed, while no DNA bands were visible in the 90 cells/(g sand) sample with and without the Mars sand simulant. The total DNA mass contained in 900 cells was calculated to be 15.3 pg (i.e., 1.53 pg in 0.1 g sand sample we evaluated). We tested and compared the influence of the eluate of Mars sand simulant and DNA adsorption onto Mars sand simulant based on optical absorbance measurements. Our findings suggest that the mechanism by which the Mars sand simulant prevents PCR is through the adsorption of DNA onto the Mars sand simulant.

Influence of the DEA Concentration on Structural and Optical Properties of Nanodot PbS Thin Films Growth by Chemical Solution Deposition: Unveiling Dual Optical Absorption Edges

The present paper presents a straightforward method for producing thin film layers of sulfide quantum dots (PbS-QDs) on a glass substrate using chemical solution deposition (CSD) assisted by dipcoating technique. The deposited PbS-QDs films were subjected to a comprehensive analysis using atomic force microscopy (AFM), energy dispersive X-ray (EDX) scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis–IR absorption, and photoluminescence spectroscopic (PL) techniques to investigate the effects of varying concentrations of diethanol amine (DEA) on their morphology, crystal structure, elemental composition, light absorption, and emission characteristics. The spherical shape of the PbS-QDs was confirmed by AFM and SEM images with average sizes around 100 and 50 nm, respectively. The energy dispersive X-ray (EDX) analysis provides evidence the existence of Pb and S elements within the PbS matrix. X-ray diffraction (XRD) results validate that the deposited films exhibit high crystallinity, with a preferential orientation along the (111) plane and a face-centered cubic lattice structure of PbS. The crystallite size of PbS is measured to be 46.6 nm. Based on the optical absorption measurements, we have determined the size range of PbS nanocrystals to be between 4.3 and 11.5 nm. The optical studies reveal the presence of two optical absorption edges within the visible and infrared spectrum, two direct band gap energy, two cut-off wavelengths, two confinement energy, two Urbach energy tail, and dual emission peaks of PbS-QDs at room temperature. The analysis reveals the presence of two distinct band gap energies, one in the visible range (1.3–2.28 eV) and the other in the infrared range (0.65–0.88 eV), which can be attributed to the formation of two distinct sizes of quantum dots situated in two different layers. The first layer, deposited directly on the glass substrate, comprises quantum dots with an average size of approximately 5.2 nm, while the second layer contains quantum dots with an average size of about 9.5 nm. This ability to tune the band gap of PbS in the visible range up to the IR band (0.65–2.28 eV) is a critical feature that holds the potential for the development of innovative optoelectronic devices.

Magnetic and optical properties of ZnO nanoparticles and nanorods synthesized by green chemistry

ZnO nanostructures have attracted considerable attention because of their physicochemical properties and applications as antibacterial agents, photocatalytic reactions for pollutant removal, and electronics. Hence, efficient production and knowledge of their properties under different synthesis conditions are essential. Biosynthesis has emerged as an excellent growth-directing method for synthesizing nanomaterials, representing a soft and cleaner alternative for their production. In this study, we synthesized different ZnO nanostructures using a soft chemistry method at different growth temperatures, from 200 to 800 °C every 200 °C. The crystalline structure was estudied by x-ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HRTEM). The shape and size were studied by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM), which revealed a ZnO hexagonal phase with two shapes: nanoparticles (NPs) with irregular shapes and nanorods of different sizes. The optical properties were studied by Raman and UV-visible spectroscopy, and optical absorption measurements showed bandgap tuning of the produced nanostructures. Finally, the magnetic characteristics of the samples demonstrated magnetic anisotropy due to the preference for crystalline formation and the size of the nanoparticles. The magnetic interaction between the two types of NPs increased the diamagnetism associated with the nanorods.