NIR Absorption Spectra Research Articles

Gamma-ray irradiation-induced effects on Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glass: Structural, optical, luminescence, and radiation shielding properties

In the present study, we report the gamma (γ) ray irradiation-induced structural, optical, luminescence and radiation shielding properties of Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glasses prepared by melt-quenching technique. It was evidence of the slight reductions in density and refractive index while maintaining stable optical properties upon the γ irradiation. Additionally, increased molar volume and polarizability indicated a less compact network. Raman spectroscopy shows broadened peaks and intensity reductions at key vibrational modes. The UV–Vis–NIR absorption spectra reveal the shift in the absorption edge and reduction in the intensities of Er³⁺ absorption bands (around 450, 520, 550, and 650 nm) with higher radiation doses, indicating radiation-induced damage. It was found that the band gap values decreased from 2.58 eV to 1.30 eV for un-irradiated glass to 90 kGy irradiated glass, and Urbach energy was found to increase from 0.18 to 1 eV respectively, indicating structural disorder and localized states within the band gap. PL emission spectra demonstrated intensity changes and peak shifts with γ radiation dose while maintaining a dominant green emission from 4S3/2 → 4I15/2 and 2H11/2 → 4I15/2 transitions, supported by the CIE diagram analysis. The NIR emission spectra also displayed a peak at 1530 nm with decreasing intensity, indicating defect-induced non-radiative recombination centres. Luminescence lifetime decay profiles indicated reduced lifetimes at higher γ doses, suggesting introduced non-radiative decay pathways. Furthermore, Phy-X software analysis highlighted effective γ-ray shielding influenced by chemical composition and photon flux, with MAC sharply decreasing to 1.8 cm2/g at 0.1 MeV and stabilizing, while LAC showed reduced attenuation efficiency at higher energies. HVL and TVL increased with energy, stabilizing around 4–5 cm and 15–16 cm, respectively, necessitating thicker materials for effective shielding at higher photon energies. MFP rapidly increased to 6–7 cm at 2 MeV, stabilizing at higher energies, while Zeff decreased sharply before stabilizing around 1 MeV. The EBF and EABF trends exhibited higher values at low energies, stabilizing at higher energies, indicating effective photon interaction and resonance effects.

Influence of Co-formers on the radiation shielding properties of zinc incorporated barium borate glasses for radioactive waste storage applications

The primary objective of the current investigation is to explore a novel series of Dy3+ions doped Zinc incorporated barium borate glasses synthesized through the classic melt quenching approach for the application of radiation defending. In this examination, the co-formers TeO2, Bi2O3, V2O5 and one of the glass formers P2O5comprised individually with the glass network. The non-crystalline phase of fabricated glasses symbolized by the empirical formula (64−x) B2O3+xA+15BaO+20ZnF2+1Dy2O3 (where x = 0, 20; A = P2O5, TeO2, Bi2O3, V2O5) and these pristine glasses were characterized by various techniques. Structural investigations were done by XRD, FTIR approach. FTIR analysis reveals the existence of functional group and their corresponding band assignments in the glass samples were recognized. The UV–Visible–NIR absorption spectra elucidates the optical properties including the energy transitions concerned with the trivalent Dysprosium ion, Urbach energy, direct and indirect bandgap energy using Tauc's plot method. The vanadium pentoxide (V2O5) co-former comprised glass network exhibits highly contrary behavior in optical scrutiny compared to other glasses. The Physical, structural attributes along with elastic properties are deliberated for the prepared glasses. The ionicity and covalency estimation validates the fact that the present glass samples exhibit maximum ionic nature. Radiation shielding parameters such as mass attenuation coefficients (MAC), half value layer (HVL) and effective atomic number (Zeff) for the titled glasses have been enumerated, discussed and reported. Among the prepared glasses, Bi2O3 co-former comprised glass exhibit better efficiency than the available concrete shielding materials.

Enhanced white light emission and quantum efficacy of borate-zinc–lithium-aluminium glasses doped with Dy2O3 for potential white light emission applications

The pursuit of efficient and enhanced white light emission in glasses doped with rare earth ions is a noble endeavour, one that has the potential to revolutionise many industries and benefit countless individuals. In view of this, we have prepared the Dy3+ ions doped Borate-Zinc–Lithium-Aluminium glasses via melt-quenching methods and their properties were meticulously studied using XRD, Raman, FTIR, DSC, Luminescence and time decay kinetic studies. To evaluate the influence of Dy2O3 doping, various physical parameters were analysed. The integration of Dy2O3 into the host glass matrix causes significant changes in the numerous physical parameters due to the geometrical structural change, resulting in the formation of non-bridging oxygens (NBOs), resulting in the increased compactness, thus the density and refractive index of the glasses. The DSC profile analysis reveals the thermal stability of the glasses. The UV–visible–NIR absorption spectra reveal the presence of a pronounced peak, owing to a hyperfine transition and other transitions dependent on the host. Furthermore, the Judd-Ofelt theory was applied to support the experimental results and evaluate the radiative parameters and efficiency. It was discovered that the JO parameters are in the following order: Ω2> Ω6> Ω4. The luminescence emission enhancement was observed with Dy2O3, up to 0.75 mol%; beyond that, the concentration quenching effect was observed. The glasses were proficiently fitted to the Inokuti-Hirayama model. Colorimetric parameters such as CIE coordinates, correlated colour temperature, and yellow-to-blue intensity ratios were estimated. It was discovered that, the sample containing 0.75 mol% of Dy2O3 doped glass is capable of white light emission with 72 % efficiency under excitation of 349 nm. Overall, present studies demonstrate that the thermal stability of glasses with phonon energy of 1330 cm−1, when stimulated at 349 nm and capable of producing white light, offers considerable benefits in relevant applications in the field of wLEDs.

Spectroscopic, physicochemical characterizations and photonics applications on boron subphthalocyanine chloride as organic electronics

This work shows the structural, thermogravimetric, optical, and electrochemical properties of boron subphthalocyanine chloride (B-subPc-Cl) as organic electronic material. The Fullprof Suite program and Rietveld analysis were used to refine and index the crystal structure of B-subPc-Cl. The thermogravimetric analysis (TGA) and the differential thermogravimetric analysis (dTG) were used to study the kinetic thermogravimetric factors using the Horowitz-Metzger's and Coats-Redfern methods. The absorption spectra of B-subPc-Cl contain two strong absorption bands (Soret-like band and Q-like band). The oscillator strength and electrical dipole strength were estimated by using a Gaussian fitting of the molar absorptivity (εmolar) of the B-subPc-Cl. The HOMO-LUMO and the band gap of B-subPc-Cl were calculated by using cyclic voltammetry measurement. Details of the UV-Vis –NIR absorption spectra and optical band gap for B-subPc-Cl are also provided. Density-functional theory (DFT) method has been utilized to obtain geometrically optimized structure for the studied compound. The theoretical calculations agreed with the experimental results. The obtained results point out the prospects of B-subPc-Cl for the organic electronic applications.
 KEY WORDS: Subphthalocyanine, Optical properties, TGA, Cyclic voltammetry, DFT method
 Bull. Chem. Soc. Ethiop. 2024, 38(2), 527-538. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i2.19

Engineered praseodymium sulfide nanocarrier and supramolecular association of anticancer drug for effective delivery to breast cancer cells

Metal sulfide nanoparticles are synthesized for their biomedical applications, including cancer drug targeting. This paper reports a novel nanocomposite made of praseodymium sulfide nanoparticles and poly-cyclodextrin. The praseodymium sulfide nanoparticles were synthesized hydrothermal, autoclaving the nitrate precursors at 150 °C for 18 hours. The material is characterized using XRD and shows an orthorhombic crystal system with high crystallinity. The size and morphology of the nanomaterial were optimized. The material shows a rod-shaped morphology, as seen in the TEM image, with 150 ± 3 nm length and 25 ± 5 nm width. Particle size analysis supports this size range. The colloidal particles were stable in the aqueous medium without precipitation at neutral pH. The elements in the material in the polymer-coated form and their electronic states are studied by X-ray photoelectron spectroscopy. Thermogravimetry confirms that the material contains about 18.5% of the weight of the polymer. The material has an observable magnetic property at room temperature due to the praseodymium element. The UV–vis–NIR absorption spectrum of the material shows a long absorption range that extends to 1200 nm. The drug 5-fluorouracil is encapsulated in the nanoparticles through host: guest association, and its release profile is analyzed. The release is modulated at a slightly acidic pH, indicating the pH-tunability. The nanoparticles and 5-fluorouracil were taken in the w/w ratio of 2:1 (2/1 mg in 1 mL of deionized water). Further, the in vitro anticancer activity of the drug-encapsulated material is screened on breast cancer and non-cancerous cell lines. The IC50 values are reported, and the advantageous properties of the material as drug carriers are discussed.

Judd-Ofelt analysis and NIR spectroscopy properties of Nd3+-doped Na2O/NaF-Al2O3-Y2O3-P2O5 glass and transparent glass-ceramics containing NaYP2O7 crystals

In the present work, the Nd3+-doped Na2O/NaF-Al2O3-Y2O3-P2O5 glass and transparent glass-ceramics were fabricated by conventional melting-quenching and subsequent heat treatment. The glass structure was studied by XRD, DSC, and FTIR spectrum, the fluorophosphate glass exhibits a more compact cross-link network. The UV–Vis–NIR absorption spectra, Judd-Ofelt theory, and photoluminescence spectra were used to explore the absorption and NIR spectroscopic features of the Nd3+-doped phosphate and fluorophosphate glasses. Under the excitation of 582 nm, the intense NIR emission in the Nd3+-doped glasses originating from the internal transition 4F3/2 → 4IJ/2 (J = 13, 11 and 9) was observed, and the transition 4F3/2 → 4I11/2 (1053 nm) is the most dominate. The transparent glass-ceramics (GC) was fabricated via heat treating on the precursor glass (PG) at Tg+100 °C, and the precipitation of NaYP2O7 crystals in GC was confirmed by XRD and SEM. With the benefit of the existence of the NaYP2O7 crystals, the Nd3+-doped GC exhibits higher NIR emission intensity, higher quantum efficiency (72.85% and 84.11%), larger σ(λp) values of 4.24×10-20 cm2 and 4.86×10-20 cm2, larger σ × Δλeff values of 10.22×10-26 cm3 and 11.67×10-26 cm3 than that of PG. These results indicate that the Nd3+-doped phosphate and fluorophosphate glasses and glass-ceramics may be used as a gain medium for 1053 nm laser emission.

Syntheses, structures and photophysical properties of Ni/Co[sbnd]Ln coordination polymers

The new Ni/Co-Ln coordination polymers (CPs), {[LnNi0.5(2,5-pydc)(ox)(H2O)x]·yH2O}n (Ln = Pr 1, Nd 2, x = 4, y = 2; Gd 3, Tb 4, Dy 5, x = 3, y = 1; 2,5-H2pydc = pyridine-2,5-dicarboxylic acid, H2ox = oxalic acid); {[Er2Ni(2,5-pydc)3(ox)(H2O)4]·2H2O}n6; {[LnCo0.5(2,5-pydc)(ox)(H2O)x]·yH2O}n (Ln = Pr 7, Nd 8, x = 4, y = 2; Tb 9, x = 3, y = 5) were successfully synthesized by the hydrothermal methods, and their crystal structures were characterized by single-crystal X-ray diffraction. With the participation of the auxiliary ligands (ox2−), the main ligands (2,5-pydc2−) adopt four coordination modes and make these polymers exhibit three kinds of crystal structures. CPs 1, 2, 7 and 8 are isomorphous and exhibit 2D layers which are further connected to form the 3D structure by hydrogen bonds. The other four CPs are bridged into the 3D network structure by 2,5-pydc2- and ox2−. All the polymers are characterized by IR spectro, Roman spectro, thermogravimetric analysis and X-ray powder diffraction. The UV–vis–NIR absorption spectra and Vis fluorescence excitation and emission spectra of nine coordination polymers are measured and analyzed. All the CPs show ligand-to-metal charge transfer (LMCT) transition emission of NiII/CoII–ligands, while some of the CPs show weak characteristic luminescence of LnIII ions.

Evaluating the Phosphorescence duration of Zn2P2O7 glass–ceramic activated by Dy3+/Pr3+ for LED applications

The present study focuses on investigating the phosphorescence efficiency of binary zinc–phosphate glasses co-doped with dysprosium and/or praseodymium oxides together with their corresponding glass ceramics. The studied glass series was prepared directly by the conventional melting and quenching method. Differential thermal analysis (DTA) indicated an exothermic peak at 550 °C that was applied to yield glass-ceramic samples. The major monoclinic phase of Zn2P2O7 was detected by X-ray diffraction (XRD). FTIR and SEM–EDAX were applied to identify the structural morphology of the prepared samples. The optical efficiency was characterized through UV–Visible–NIR absorption spectra and photoluminescence analysis. Both light emissions and their corresponding lifetimes were enhanced significantly in glass–ceramic. These samples display high CRI, low color temperature, and CIE values comparable to those expected for pure white-light and warm yellow emitting diodes.

The effect of oxygen vacancies on the color formation of aquamarine

Oxygen vacancy is an inherent defect of aquamarine crystals. The concentration and properties of this defect have an essential influence on aquamarine crystals and optical properties. This paper reports that blue in aquamarine crystals is due to the interaction between Fe2+ and oxygen vacancy. Infrared and Raman spectra showed that more Fe2+ replaced Al3+ in dark sample A than in light sample B. Oxygen vacancies were found in all samples. Dark sample A strongly absorbed the 830 nm band associated with Fe2+ in the UV–Vis–NIR absorption spectrum. The band gap of dark sample A was smaller than that of light sample B, and the difference in band gap was related to the concentration of oxygen vacancies. X-ray Photoelectron Spectroscopy showed that the oxygen vacancy concentration in sample A was higher than that in sample B, which showed that the oxygen vacancy concentration affected the color depth of aquamarines.

Monitoring of banana’s optical properties by laser light backscattering imaging technique during drying

Banana drying is an important process that used to extend the shelf life and increase the marketability of the dried banana. However, this process can lead to changes in weight loss, firmness, and color, which may influence consumer acceptance. As a result, it is crucial to monitor these changes to maintain the desired quality. Therefore, the aim of this study was to assess the quality of sliced bananas during the drying process by simultaneously monitoring their optical and physical properties using laser light backscatter imaging, near-infrared spectroscopy, and electrical impedance spectroscopy techniques. Banana sliced were prepared with 10 mm thickness and immersed into 4% ascorbic acid solution and water as treated and control samples dried at 50 °C for 6 h. The parameters measured were weight loss, color, firmness, NIR absorbance in the range from 740 to 1700 nm and electrical impedance in the frequency range from 30 kHz to 1 MHz. Absorption, reduced scattering and diffusion coefficients, penetration depth and full width at half maximum (FWHM) were computed on the LLBI signal at wavelengths of 532, 635, 780, 808, 850 and 1064 nm. The results showed that both the drying time and the ascorbic acid treatment and their interaction affected the measured values. The strong NIR absorption spectrum changes observed at wavelengths of 1064 and 1416 nm. The least squares partial regression model (PLSR) was performed with high accuracy for weight loss (%) and relaxation time (ms) at a coefficient of determination (R2) of 0.940 and 0.945 with a mean square error (RMSE) of 3.748 and 0.001, respectively. The electrical impedance spectral changes were found in the frequency range from 60 Hz to 1 MHz. The most sensitive laser wave lengths to evaluate optical properties were 532, 635, 780 and 1064 nm. Therefore, laser backscatter imaging together with NIR spectroscopy and impedance spectroscopy is a promising technique to assess the quality of sliced bananas during the drying process.Graphical abstract

SnO2-Cu2S nanocomposites: Structural and optical properties with enhanced photocatalytic activities for ciprofloxacin antibiotic and methylene blue dye degradation

Pharmaceutical products and industrial dyes released to water bodies have become major environmental concerns and applications of nanomaterials for their remediation have been receiving a lot of research attention in recent years. In this connection, different SnO2–Cu2S nanocomposites (NCs) have been synthesized by growing Cu2S over previously prepared SnO2 nanocrystals by taking different molarities of copper and sulphur precursors. The pure SnO2 nanocrystals have been prepared by the chemical co-precipitation method combined with calcination of the precipitated materials at 300 °C. X-ray diffraction (XRD) pattern of the pure SnO2 nanocrystals shows the formation of tetragonal crystal structure. UV–visible–NIR absorption spectrum of the pure SnO2 nanocrystals records absorption peak in the UV region, while the Tauc's plot estimates the band gap of SnO2 to be 3.93 eV. Photoluminescence (PL) and electron paramagnetic resonance (EPR) studies reveal the presence of oxygen vacancies in the pure SnO2 nanocrystals. XRD patterns of the NCs comprise of diffraction planes from both tetragonal SnO2 and monoclinic Cu2S. PL studies show presence of both oxygen vacancies and copper vacancies in the NCs. Further, presence of copper vacancies has been evidenced in the EPR signals of the NCs. The NCs show significantly enhanced photocatalytic activities for degradation of ciprofloxacin (CIP) antibiotic and methylene blue (MB) dye under simulated sunlight irradiation, which is attributed to type II heterojunction formation between SnO2 and Cu2S. The NC with the best performance as a photocatalyst degrades 96% of CIP after 120 min and 98% of MB after 210 min of light exposure.

Exploration of Optical and Radiative Properties of Fluorinated β-keto Carboxylate Tb3+ Complexes Emanating Cool Green Light.

Tb3+ complexes with β-ketocarboxylic acid as main ligand and heterocyclic systems as auxiliary ligand were synthesized and analyzed to assess their prospective relevance as green light emitting material. The complexes were characterized via various spectroscopic techniques and were found to be stable up to ≈ 200 ℃. Photoluminescent (PL) investigation was performed to assess the emissive nature of complexes. Longest luminescence time of decay (1.34ms) and highest intrinsic quantum efficiency (63.05%) were fetched for complex T5. Color purity of complexes was found to be in range 97.1 - 99.8% which demonstrated the aptness of these complexes in green color display devices. NIR Absorption spectra were employed to evaluate Judd-Ofelt parameters to appraise the luminous performance and environment encircling Tb3+ ions. The JO parameters were found to follow the order: Ω2 > Ω4 > Ω6 and suggested the higher covalence character in complexes. Theoretical branching ratio in the range 65.32 - 72.68%, large stimulated emission cross section and narrow FWHM for 5D4 → 7F5 transition unlocked the relevance of these complexes as a green color laser media. Band gap and Urbach analysis were consummated via enforcing nonlinear curve fit function on absorption data. Two band gaps with values in between 2.02 - 2.93eV established the prospective use of complexes in photovoltaic devices. Energies of HOMO and LUMO were estimated employing geometrically optimized structures of complexes. Investigation of biological properties accomplished via antioxidant and antimicrobial assays which communicated their applicability in biomedical domain.

A comparative study on nonlinear optical properties of zinc porphyrins analogs: Coordination atoms and group effects

AbstractDensity functional theory (DFT) has been carried out to investigate the electronic characteristics, UV–VIS–NIR absorption spectra, and nonlinear optical (NLO) properties of two series of zinc porphyrin analogs (FPD‐Nxand TPD‐Nx,x = 0–4) with donor‐π‐donor frameworks. The design of these analogs is based on previously synthesized furan‐linked zinc porphyrins (FPDs) and thiophene‐linked zinc porphyrins (TPDs). It is noted that their electro‐optical features are sensitive to the numbers of N‐coordination atoms and the attached groups. A dramatic enhancement of static first and second hyperpolarizabilities (β0andγ0) occurs when two furan/thiophene rings are attached to the zinc porphyrin. Among the two series, FPD‐N3 and TPD‐N3 have the largestβ0values of about 7600 a.u. The staticγ0values of these complexes range from 0.41 × 106to 1.79 × 106 a.u. The FPD‐Nxhas a largerγ0value than the corresponding TPD‐Nx, but theγ0value of FPD‐N2 is close to that of TPD‐N2. In the dynamic NLO process, the electro‐optical Pockels effect, second harmonic generation, and electro‐optic Kerr effect can be enhanced at the wavelength of 1907 nm. This study provides a new strategy for the experimental design of high‐performance NLO materials.

Orbital Degree of Freedom in Conducting Platinum–Dithiolene Complex Salts

We report experimental evidence for the orbital degrees of freedom in anion–radical salts consisting of metal–dithiolene complexes, obtained by a simple method. We observed the NIR absorption spectra of the 2D molecular conductors Me4Q[Pt(dmit)2]2 (Q = N, P, and Sb, dmit = 1,3-dithiole-2-thione-4,5-dithiolate), which shows a phase transition from the metallic phase to the semiconducting and charge-ordered phase, and analyzed the orbital levels of dimers [Pt(dmit)2]2 near the Fermi energy. The highest-energy electrons in the charge-ordered phase occupied the bonding orbitals, whereas those in the metallic phase occupied the antibonding orbitals. The redistribution of charges and the replacement of the outermost orbitals co-occurred for all dimers in Me4Q[Pt(dmit)2]2. This phenomenon differs from that in palladium analogs, in which the replacement of the outermost orbitals does not occur or occurs only for half of all dimers. Our experimental results revealed that anion–radical salts consisting of metal–dithiolene complexes have a variety of orbital distributions.

The acceptor-donor pair recombination of beryllium-treated sapphires

Recently, the concept of Fe3+-Ti4+ mixed acceptor states in the energy band gap of sapphire has been proposed as the cause of blue coloration. The blue color in sapphire is faded and turns yellow by beryllium heat treatment. It has been revealed as the color center in Be-treated yellow sapphires. In this work, the mechanism of such phenomena was explained and discussed. The experiment was set by preparing sapphire samples from Songea, Tanzania, into four color groups (purplish blue, light blue, light yellow with dark zone, and light green). One sample from each group, altogether four, has been heat-treated with beryllium. The colors of Be-treated samples show fading of blue coloration and adding the yellow component to the samples. The analyses and spectroscopic testing were conducted on both the untreated and treated samples, in each group which consisted of one natural and one Be-treated sample. The content of color-related trace elements such as Be, Mg, Ti, Fe, and Cr was measured by the LA-ICP-MS. The oxidation state of Fe [III] was confirmed by X-ray absorption spectroscopy. Each color group showed quite similar UV–Vis–NIR absorption spectra for the natural and the Be-treated ones, regardless of differences in their color and treatment. However, their UV–Vis–NIR polychromatic excitation spectra were different, leading to the possible detection of blue color suppression due to the recombination of Fe3+-Ti4+ mixed-acceptor states by the Fe3+-Be2+ mixed donor states for Be-treated samples. Hence, the acceptor-donor pair recombination has been proposed for the blue color fading in beryllium-treated sapphire samples.

Effect of Dysprosium and Samarium RE ion Co-doping on photoluminescence behaviour of novel alkali fluoride bismuth borate glasses: A white LED material

Being inspired from the good spectroscopic traits of alkali fluoride doped borate glasses, a glass series with composition 60B2O3 + 30LiF +10Bi2O3 + (1-x) Dy2O3 + xSm2O3 (where x = 0, 0.2, 0.5, 0.7 and 1 mol%) was prepared by melt quench technique and their Structural, Physical, Optical and Lifetime decay properties were studied and analysed. Prepared samples were X-ray amorphous and their FTIR spectra confirmed that the network is composed of bismuth and borate units. Linear and Non-linear optical properties were studied via UV–Vis–NIR absorption spectra and the variation was found to be influenced by the ratio of RE ions (Dy3+ and Sm3+). Negative values of bonding parameter (δ) were obtained for both the RE ions by nephelauxetic effect and suggested that ionic character of prepared glasses was enhanced by Sm3+ ion co-doping. Emission spectra were recorded for a variety of excitation wavelengths and CIE coordinates, Correlated Colour Temperature (CCT), Colour Rendering Index (CRI) and Colour purity % were calculated. Lifetime decay curves of Dy3+ level 4F9/2 and Sm3+ level 4G5/2 were recorded. CIE coordinates of all compositions, under excitation wavelength 349 nm were displayed in 1931 CIE diagram that indicated improved cool white light emission in Dy3+ and Sm3+ co-doped matrix. The obtained colour parameters inferred that a single matrix is capable of emitting diverse colours with variation of excitation wavelengths and RE ion concentration.

Air-processed hole-conductor–free and printable infrared light responded carbon-based perovskite solar cells using up-conversion NaYF4:Yb3+, Er3+ nanoparticles

The introduction of up-conversion materials converting near infrared light into useable visible light has been proven to be a promising strategy for improving the performance of perovskite solar cells. In this work, the up-conversion material of NaYF4:Yb3+, Er3+ nanoparticles (NPs) were successfully prepared by one-step hydrothermal route and incorporated into Al2O3 as the scaffold layer for the air-processed carbon-based mesoscopic perovskite solar cells (MPSCs). FESEM shows that the size of NaYF4:Yb3+, Er3+ nanoparticles is about 100 nm and there is no obvious agglomeration. The UV–vis–NIR absorption spectrum of the mixed scaffold layer demonstrates a distinct infrared light response. The infrared photoelectric efficiency and EQE tests were used to verify that NaYF4:Yb3+, Er3+ nanoparticles improved the photo response of the device in the infrared region, thereby improved the photoelectric performance of the MPSCs. An optimal efficiency of 13.04% was obtained by incorporating 25 wt% NaYF4:Yb3+, Er3+ nanoparticles into the Al2O3 scaffold layer, which shows a 20.6% increase in conversion efficiency when compared with the device without using the up-conversion material (10.81%). The optimized carbon-based MPSCs also show an infrared responded PCE value of 0.11% under infrared irradiation from 800 to 1100 nm. This paper shows that the up-conversion material expands the light response of solar cells to the infrared region and provides an effective method for the preparation of high-efficiency perovskite solar cells.

Modulating carrier density of the (Ag)x(MoO3)y system to enhance SERS:Localized surface plasmon resonance contribution

Semiconductors typically exhibit long-wavelength LSPR absorption in the infrared region due to lower carrier density. Tuning the carrier density of semiconductors and blue-shifting their LSPR absorption to the visible and near-infrared region has always been a great challenge. Herein, we discussed how the controllable carrier of (Ag)x(MoO3)y composite influences the LSPR based on SERS test and UV–Vis–NIR absorption spectra. We were surprised to find that the LSPR absorption wavelength can be easily tuned from 950 to 735 nm by changing the sputtering power of MoO3 of the (Ag)x(MoO3)y composite. This shows that LSPR can be precisely adjusted by increasing the semiconductor content and even the carrier density. In addition, the carrier density was measured by Hall effect to investigate the SERS intensity change caused by electromagnetic (EM) enhancement, and obtain the relationship between the two. The findings of this work provide an idea for tunable LSPR and the research of EM contributions to SERS.

Augmentation of photophysical features and Judd-Ofelt analysis of extensively green glowing terbium (III) complexes with nitrogen donor ancillary ligands.

Six green glowing terbium (III) complexes were fabricated via grinding method utilizing a prime organic ligand (L) and nitrogen donor ancillary ligands. Characterization of synthesized complexes was accomplished through various spectroscopic techniques. The significant thermal stability was determined by thermogravimetric analysis while the energy bandgap and Urbach energy were investigated through diffused reflectance spectra of these complexes. The peak observed at 548nm in emission spectra is responsible for the virescent color of these complexes. Color purity, decay time, quantum yield, and emission intensities of ternary complexes were significantly improved as compared to binary ones due to the synergistic effect of ancillary ligands. Judd-Ofelt parameters were determined by the NIR absorption spectrum, which claims the asymmetric environment around the terbium (III) ion. CCT values advocate the applicability of these complexes in green light-emitting materials as a cool light source. The biological assignments reveal the significance of these complexes as potent antioxidants and antimicrobial agents. The energy transfer process highlights the enhancement of luminescence in these complexes via the synergic effect of ligands. Our investigation portrays that these complexes can be employed in laser technology, display devices, semiconductors, biological fields, and optoelectronic devices.

Utilization of Judd-Ofelt theory to assess the photophysical properties of β-keto carboxylate Tb(III) complexes with heterocyclic secondary sensitizer

One binary and five ternary green glowing Tb(III) complexes with β-keto acid as primary sensitizer and heterocyclic aromatic system as secondary sensitizer, were synthesised by an eco-friendly method and characterized via various spectroscopic techniques. The assessment of photoluminescent properties in solid complexes and in solution phase with DMSO as solvent, revealed the bright green emission of complexes on irradiation of UV light due to 5D4 → 7F5 transition, whose intensity persistently increased on insertion of secondary sensitizer. Higher relative quantum yield in ternary complexes communicated the contribution of secondary sensitizers in enhancement of luminescence. Judd-Ofelt parameters (Ω2, Ω4, Ω6) were evaluated from NIR absorption spectra of complexes. Higher Ω2 value in complexes demonstrated the higher covalence character and asymmetry around Tb(III) ion. Radiative, nonradiative transition probabilities, radiative life time, branching ratios and luminescence efficiency were also estimated. Complex T6 reported to have 72.5% efficiency which signalizes superb luminescence performance of this complex. Colorimetric parameters were obtained in solid as well as solution form. Exquisite color purity and CCT value > 4000 K established these complexes as cold green light source. Band gap energy and Urbach band tail, obtained via nonlinear fitting of absorption coefficient, turned out to be in semiconductor range thus can have materiality in various photonic devices. The large value of stimulated emission cross section and narrow full width at half maxima (FWHM) of 5D4 → 7F5 emission peak suggested the prospective use of synthesised complexes as laser media for green color lasers.