Solid-state Diffuse Reflectance Research Articles

Heterostructured S-TiO2/g-C3N4 Photocatalysts with High Visible Light Photocatalytic Activity

Novel heterojunctions associating graphitic carbon nitride g-C3N4 and S-doped TiO2 nanoparticles were successfully designed and prepared via a hydrothermal method and used for photocatalytic degradations. The loading in S-TiO2 nanoparticles on g-C3N4 was varied (5, 10 and 20 wt%), and the photocatalysts were characterized by XRD, FT-IR, solid-state UV-visible diffuse reflectance, photoluminescence, XPS, TEM and SEM. The S-TiO2 (5%)/g-C3N4 catalyst exhibits the highest activity for the photocatalytic degradation of the methylene blue (MB) dye under visible light irradiation. The high photocatalytic performance originates from the enhanced separation and transfer of photogenerated charge carriers. The S-TiO2 (5%)/g-C3N4 photocatalyst is stable and can be reused five times without a sharp drop in activity, indicating its high potential for wastewater remediation.

Preparation, structure and properties of a novel one-dimensional erbium (III) complex

A novel one-dimensional erbium complex [ErL2(NO3)(H2O)2]n (HL = 2-picolinic acid) was synthesized by hydrothermal methods, and its crystal structure was determined by single crystal x-ray diffraction. The complex crystallize in monoclinic system, space group C2/c with a = 15.7525(5) Å, b = 11.4958(4) Å, c = 9.7977(3) Å, β = 102.862(3) º, V = 1729.72(10) Å3, C12H10ErN3O9, Mr = 507.49, Z = 4, Dc = 1.949 g•cm-3, F(000) = 972,  = 4.901 mm-1, S= 1.119, λ(MoKα) = 0.071073 nm, R = 0.0239 and wR = 0.0668. The 2-picolinic acid ligand adopts bidentate bridging coordination mode to connect adjacent erbium ions to form a one-dimensional chain structure. A series of properties of the complex were measured by solid-state photoluminescence, solid-state diffuse reflection and differential scanning calorimetry.

Two bimetallic compounds with attractive structures and properties

Two new bimetallic lanthanide-mercury isonicotinic acid compounds were successfully synthesized through classical hydrothermal reactions using DyCl3·6H2O or LuCl3·6H2O, HgCl2, isonicotinic acid, and distilled water. The resulting compounds, [Dy2(IA)6(H2O)2(H3O)2(Hg2Cl5)2]n(3nHgCl2) (1; IA refers to isonicotinic acid anions) and [Lu(HIA)(IA)2(H2O)2Hg2Cl5]2n[3n(HgCl2)]·6nH2O (2; HIA refers to isonicotinic acid), exhibit intriguing crystal structures and photophysical properties. The crystal structures of compounds 1 and 2 were determined through single crystal X-ray diffraction, revealing their two-dimensional (2D) nature. Compound 1 displays upconversion yellow photoluminescence, attributed to the 4F9/2 → 6H13/2 electronic transition of the trivalent dysprosium ion. In contrast, compound 2 exhibits blue photoluminescent emission. The Commission Internationale de I'Éclairage (CIE) chromaticity coordinates of (0.4874, 0.5115) for 1 and (0.1225, 0.0678) for 2. The correlated color temperatures (CCT) are 2960 K and 5503 K for compounds 1 and 2, respectively. Furthermore, the semiconductor band gaps for compounds 1 and 2, determined by solid-state diffuse reflectance experiments, are 2.92 eV and 4.75 eV, respectively. Additional insights into their thermal stability are provided via thermogravimetric analysis (TG) results.

A new zero-dimensional (0D) hybrid bismuth (III) halide: Synthesis, crystal structure, thermal analysis, photophysical properties and DFT calculations

Low-dimensional organic-inorganic hybrid Bi(III) halides, with organic N, O-heterocycles, are promising solid-state photoluminescent materials, but are underexplored. In this work, we present the synthesis and characterization of a novel bismuth (III) hybrid salt, namely (C8H12NO)4[Bi2Cl10] (referred as (1)). (1) was synthesized using a solvent-evaporation method and extensively characterized using various techniques. The crystal structure of (1) was determined to be zero-dimensional (0D). In this structure, the individual bioctahedral [Bi2Cl10]4− dimers, which share edges, are completely isolated from each other. These dimers are separated by large 4-methoxybenzylammonium cations (C8H12NO)+. The latter are crucial for the crystal structural stability by balancing [Bi2Cl10]4-dimer charges and maintaining overall integrity. Solid-state diffuse reflectance UV–Vis spectrum demonstrates that (1) is a semiconductor with a band gap of 3.32 eV. Its photoluminescence spectrum exhibits intense blue emission when exposed to UV light, with CIE chromaticity coordinates of (0.22, 0.21). Theoretical calculations suggest that the emission with multiple centers originates both from a charge transition between (C8H12NO)+ and Bi2Cl104− ions and from excited-state proton transfer (ESPT) processes related to fluorescence properties. These ESPT processes occur through C–H…π and C–H…O intermolecular hydrogen bonding between the organic cations.

Preparation, crystal structure, time-dependent density theory and properties of a novel organic-inorganic hybrid up-conversion luminescence tetranuclear complex

A novel up-conversion luminescence tetranuclear sodium complex [Na4(5-(carboxymethyl 2-oxo-propyl) amino isophthalic acid)(H2O)9] is synthesized by a solvothermal reaction, and its crystal structure is determined by single-crystal X-ray diffraction. The title complex crystallizes as a triclinic system with the P [Formula: see text] space group and exists as an isolated tetranuclear complex. Numerous intermolecular hydrogen bonds and van der waals forces form a three-dimensional supramolecular network. Solid-state diffuse reflectance data show that there is a wide optical band gap of 2.91 eV. The solid-state photoluminescence spectrum reveals that the complex shows an up-conversion emission in the blue region of the light spectrum. Time-dependent density functional theory calculations reveal that this emission can be attributed to ligand-to-ligand charge transfer.

In situ synthesis, crystal structure and photophysical properties of a new binuclear europium compound

A new europium compound [Eu2(H2O)8(MBA−)4](2MBA−) (1; MBA− = methylsulfanyl-benzoic acid anion) was synthesized via an in situ reaction of EuCl3·6H2O, 4,4′,4″-(1,3,5-triazine-2,4,6-triyltrisulfanediyl)tribenzoic acid, methanol and distilled water under hydrothermal conditions. The crystal structure is characterized by single-crystal X-ray diffraction and features a binuclear structure. The molecules are interlinked via hydrogen-bonding interactions to form a one-dimensional (1-D) supramolecular chain. A photoluminescence measurement with solid-state samples reveals that compound 1 can emit brown upconversion photoluminescence with the maximum peak locating at 622 nm and a weaker one at 590 nm. The bands are ascribed to the characteristic emission of the 4f electron intrashell transition of the 5D0 → 7F1 and 5D0 → 7F2 of the Eu3+ ions. Compound 1 exhibits CIE chromaticity coordinates (0.557, 0.4292) and its CCT is 1871 K. The solid-state diffuse reflectance spectra reveals that compound 1 has a bandgap of 4.09 eV.

Proton conduction and electrochemical glucose sensing property of a newly constructed Cu(II) coordination polymer

The assembly between 5-sulfo-1, 2, 4-benzoic acid (H4SBTB) and Cu2+ in the presence of 4, 4´-bipyridine (Bipy) results in a novel ionic coordination polymer with two crystallographically independent hexa-coordinated Cu1 and Cu2 ions, namely, [Cu3(HSBTB)2(Bipy)3(H2O)8]n (1), which consists of an anionic Cu12(C1O1O2)2-Bipy-bridged double-chain and a cationic Cu2-Bipy-bridged mono-chain. With the aid of H-bonds, the anionic Cu12(C1O1O2)2-Bipy-bridged double-chains extend into a 2D supramolecular anionic double-layer, which is further linked by the cationic Cu2-Bipy-bridged mono-chain, resulting in a 3D supramolecular network. The H4SBTB acid exhibits a new coordination mode, i.e. one carboxyl group still remains protonated in 1. The analysis of the solid-state diffuse reflectance UV-Vis-NIR spectrum reveals that the indirect bandgap exists in 1, which was further illustrated by the theoretical calculation on the basis of Density Functional Theory (DFT) using the CASTEP program. The electrochemical studies indicate that the composite membrane of 1 with nafion shows interesting temperature-insensitive proton conduction behavior at pH = 3. Cyclic voltammograms indicate that 1 exhibits electrocatalysis to glucose oxidation in 0.1 M NaOH. The current-time (i-t) response curves reveal that 1 demonstrates sensitive and selective electrochemical oxidation sensing of glucose with an exponential detection range of 0-30 mM. The limit of detection (LOD) was calculated to be 38.74 μM.

Self-Assembly of a U(VI)-Containing Polytungstate Tetramer with Lewis Acid-Base Catalytic Activity for a Dehydration Condensation Reaction.

A novel U(VI)-containing polytungstate (U-POW) tetramer, {K1.37Na26.63[K2(UO2)4Cl0.5(OH)5.5(γ-SiW10O36)4]}·ca66H2O (U4), was synthesized using the Keggin-type precursor [γ-SiW10O36]8- and UO2(NO3)2. U4 was further characterized by single-crystal X-ray diffraction, FT-IR, Raman spectroscopy, solid-state diffuse reflection spectroscopy, ICP-OES, ESI-MS, TGA, and PXRD. The central {K2(UO2)4Cl0.5(OH)5.5} chromophore was constructed dexterously from four uranyl, four halves of K ions, 5.5 bridging μ2-OH, and disordered Cl ions, and was further stabilized by four {γ-SiW10} moieties to construct the tetramer [K2(UO2)4Cl0.5(OH)5.5(γ-SiW10O36)4]28-. Notably, U4 could work as an effective bifunctional Lewis acid-base catalyst for the synthesis of pyrazoles via the condensation of hydrazines with 1,3-diketones under mild conditions, which is attributed to the synergetic effect of the Lewis acidity of U(VI) and the Lewis basicity of {γ-SiW10}.

Use chloride to assist in constructing of penta- and nano-nucleus mixed-valent Cu(I/II) clusters and their photo-thermal properties

To prepare new series of mixed-valence polynuclear Cu(I/II) clusters, chloride ions are introduced to construct two mixed-valence polynuclear Cu(I/II) clusters for evaluating their photothermal conversion performance. X-ray single-crystal structural analysis reveals their molecular formula are {CuII[CuI(Cy3P)]4(BTA)4Cl2}·5DMF (I·5DMF, Cy3P = triscyclohexylphosphine, BTA = benzotriazole, DMF = N,N-Dimethylformamide) and {(CuII)3[CuI(PPh2Py)]6(BTA)8Cl4}·6DMF (II·6DMF, Ph2PyP = diphenyl-2-pyridylphosphine), respectively. X-ray Photoelectron Spectroscopy (XPS) and Electrospray Ionization Mass Spectrometry (ESI-MS) confirm their chemical composition and charge state. The reported two mixed-valence CuI/CuII clusters have different nucleus (penta-nucleus for I and nano-nucleus for II) and different proportion of valence state (1/4 for I vs 1/2 for II). The thermogravimetric analysis (TGA) reveals the thermal stability of both clusters is less than our previously reported penta-nucleus mixed-valence CuI/CuII clusters. Contrastively studies of their optical absorption properties by the solid-state ultraviolet diffuse reflection spectra indicate high-nucleus mixed-valence CuI/CuII cluster with higher proportion of CuII is superior to those penta-nucleus mixed-valent Cu(I/II) clusters. With the introduction of chloride ions to the structures of mixed-valence CuI/CuII clusters have not remarkably changed their photothermal conversion performance. This study provides a practicable way to construct new mixed-valence CuI/CuII clusters with different photothermal conversion performance.

Amino-Functionalized Titanium Based Metal-Organic Framework for Photocatalytic Hydrogen Production.

Photocatalytic hydrogen production using stable metal-organic frameworks (MOFs), especially the titanium-based MOFs (Ti-MOFs) as photocatalysts is one of the most promising solutions to solve the energy crisis. However, due to the high reactivity and harsh synthetic conditions, only a limited number of Ti-MOFs have been reported so far. Herein, we synthesized a new amino-functionalized Ti-MOFs, named NH2-ZSTU-2 (ZSTU stands for Zhejiang Sci-Tech University), for photocatalytic hydrogen production under visible light irradiation. The NH2-ZSTU-2 was synthesized by a facile solvothermal method, composed of 2,4,6-tri(4-carboxyphenylphenyl)-aniline (NH2-BTB) triangular linker and infinite Ti-oxo chains. The structure and photoelectrochemical properties of NH2-ZSTU-2 were fully studied by powder X-ray diffraction, scanning electron microscope, nitro sorption isotherms, solid-state diffuse reflectance absorption spectra, and Mott–Schottky measurements, etc., which conclude that NH2-ZSTU-2 was favorable for photocatalytic hydrogen production. Benefitting from those structural features, NH2-ZSTU-2 showed steady hydrogen production rate under visible light irradiation with average photocatalytic H2 yields of 431.45 μmol·g−1·h−1 with triethanolamine and Pt as sacrificial agent and cocatalyst, respectively, which is almost 2.5 times higher than that of its counterpart ZSTU-2. The stability and proposed photocatalysis mechanism were also discussed. This work paves the way to design Ti-MOFs for photocatalysis.

Importance of Nuclear Quantum Effects for Molecular Cocrystals with Short Hydrogen Bonds.

Many efforts have been recently devoted to the design and investigation of multicomponent pharmaceutical solids, such as salts and cocrystals. The experimental distinction between these solid forms is often challenging. Here, we show that the transformation of a salt into a cocrystal with a short hydrogen bond does not occur as a sharp phase transition but rather a smooth shift of the positional probability of the hydrogen atoms. A combination of solid-state NMR spectroscopy, X-ray diffraction, and diffuse reflectance measurements with density functional theory calculations that include nuclear quantum effects (NQEs) provides evidence of temperature-induced hydrogen atom shift in cocrystals with short hydrogen bonds. We demonstrate that for the predictions of the salt/cocrystal solid forms with short H-bonds, the computations have to include NQEs (particularly hydrogen nuclei delocalization) and temperature effects.

Opto-Electronic Characterization of Photocatalysts Based on p,n-Junction Ternary and Quaternary Mixed Oxides Semiconductors (Cu2O-In2O3 and Cu2O-In2O3-TiO2)

Semiconductor materials are the basis of electronic devices employed in the communication and media industry. In the present work, we report the synthesis and characterization of mixed metal oxides (MOs) as p,n-junction photocatalysts, and demonstrate the correlation between the preparation technique and the properties of the materials. Solid-state UV-visible diffuse reflectance spectroscopy (UV-VIS DRS) allowed for the determination of the light absorption properties and the optical energy gap. X-ray photoelectron spectroscopy (XPS) allowed for the determination of the surface speciation and composition and for the determination of the valence band edge. The opto-electronic behavior was evaluated measuring the photocurrent generated after absorption of chopped visible light in a 3-electrode cell. Scanning electron microscopy (SEM) measurements allowed for auxiliary characterization of size and morphology, showing the formation of composites for the ternary Cu2O-In2O3 p,n-mixed oxide, and even more for the quaternary Cu2O-In2O3-TiO2 MO. Light absorption spectra and photocurrent-time curves mainly depend upon the composition of MOs, while the optical energy gap and defective absorption tail are closely related to the preparation methodology, time and thermal treatment. Qualitative electronic band structures of semiconductors are also presented.

Synthesis, Structure, and Light Absorption Behaviors of Prismatic Titanium-Oxo Clusters Containing Lacunary Lindqvist-like Species.

Exploring new structural types of polyoxotitanium clusters (PTCs), especially those containing classical polyoxometalates structures, has always been the focus of research in the field of metal-oxo clusters. In this work, we present the synthesis and characterization of three prismatic PTCs: namely, Ti8(μ2-O)3(μ4-O)2(OnPr)6(HOnPr)2(L1)8 (PTC-237; H2L1 = 3,5-di-tert-butylcatechol), Ti12(μ2-O)6(μ3-O)8(OnPr)6(L2)12(L3)2 (PTC-238; HL2 = 1-adamantanecarboxylic acid, HL3 = 2-picolinic acid), and [Ti18(μ2-O)4(μ3-O)16(μ5-O)2(OiPr)18(L3)8](L3)2 (PTC-239). Single-crystal X-ray diffraction analyses indicate that the construction of these prismatic PTCs is based on a stepwise interlayer assembly of {Ti3} and {Ti4} substructures. The diameters of their core skeletons are in the range between 0.9 and 1.3 nm. In particular, lacunary Linqvist-like {Ti4} and {Ti5} building units are found to exist in the structures of PTC-237 and PTC-239. According to the solid-state UV-vis diffuse reflectance measurements, the absorption band of 3,5-di-tert-butylcatecholate-functionalized PTC-237 shifts toward the visible-light region, giving a smaller optical band gap of 1.56 eV in comparison to PTC-238 (3.36 eV) and PTC-239 (3.25 eV).

Mechanochemical route for tetra amino zinc phthalocyanine embedded PANI sensitized Fe2O3 heteroarchitecture for photodegradation of dyes under the influence of low power LED light source

In the present work, we demonstrate a facile, simple and effective solvent-free rapid mechanochemical approach for the synthesis of tetra amino zinc phthalocyanine engrained PANI sensitized Fe2O3 hybrid (TAZnPc-PANI@Fe2O3) photocatalyst. Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), Solid state diffuse reflectance spectrophotometer have been used to characterize the structure, size, morphology and optical properties of TAZnPc-PANI@Fe2O3 photocatalyst. Cationic methylene blue (MB) and anionic Eosin Y (EY) dyes were chosen as modular pollutants to investigate photodegradation competence of Fe2O3 alone and TAZnPc-PANI@Fe2O3 hybrid photocatalyst under the influence of the low power white LED (16 W) as visible light source. Influence of operational parameters such as catalyst loading, contact time, pH of the medium and reusability of the catalyst on the dye degradation are investigated. The obtained results established that photosensitization of Fe2O3 with tetra amino zinc phthalocyanine embedded PANI (TAZnPc-PANI) significantly enhanced the photocatalytic performance towards photodegradation of MB and EY dyes. The photodegradation of MB and EY under optimised conditions was found to be ∼95 % in 80 min.

In situ preparation, structure, photophysical properties of a novel zinc complex

A novel zinc complex [ZnI3(N-benzyl-4,4'-bipy)]·2MeOH·H3O (1) (bipy = bipyridine; MeOH = methanol) is synthesized and characterized. This complex is characterized by an isolated structure. The photoluminescence spectra using solid state samples unveiled that this complex can show a green photoluminescence emission. As revealed by the TDDFT (time-dependent density functional theory) calculation results, the photoluminescence emission should rise from an intraligand charge transfer (ILCT). The complex possesses CIE (Commission Internationale de I'Éclairage) chromaticity coordinates of 0.1305 and 0.3855. A solid-state UV-Visible diffuse reflectance spectrum shows that this complex has a narrow optical band gap of 1.87 eV.

Preparation, characterization, and photoluminescent and semiconductive properties of an iron compound

One iron compound {[Fe(bipy)3]2(SO3)(OH)4}·14H2O (1) (bipy = 2,2'-bipyridine) has been obtained from a hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. Compound 1 is characterized by an isolated (0D) structure and the iron center is coordinated by six nitrogen atoms of three bipy molecules to yield an octahedron. Photoluminescence investigation shows that compound 1 displays an emission in the green region. Time-dependent density functional theory (TDDFT) calculation reveals that the photoluminescent emission can be assigned to the ligand-to-metal charge transfer (LMCT) (from the HOMO of the bipy to the LUMO of the iron). Solid-state diffuse reflectance spectra discover that compound 1 features a narrow optical band gap of 1.82 eV, indicating that it is a potential narrow band gap semiconductor.

Hydrothermal Preparation, Crystal Structure, Photophysical Properties and Theoretical Calculation of a Cu(II) Complex

A novel Cu(II) compound [CuL2]·2H2O was synthesized by hydrothermal methods, and its crystal structure was determined by single-crystal X-ray diffraction. The title compound crystallized in the monoclinic space group P21/c as an isolated monocyte structure. The strong π…π stacking and hydrogen bonding interactions produce one-dimensional (1D) chains. A series of properties of the title compound were tested by solid state photoluminescence, CIE analysis and solid-state diffuse reflectance. The results show that the compound is a blue light emitter, CIE (0.1291, 0.0783) and has an energy bandwidth of 1.65 eV. Time-dependent density functional theory (TDDFT) calculation results show that the emission of the compound can be attributed to charge transfer from metal to ligand and ligand to ligand (MLCT and LLCT). A novel Cu (II) complex is synthesized via hydrothermal preparation, which is characteristic of an isolated structure, at the same time, it displays a narrow and intense photoluminescence emission band in the blue region and theoretical study reveals that the photoluminescence emission is originated from the metal-to-ligand and ligand-to-ligand charge transfer transition.

Synthesis, characterization, and photocatalytic disinfection studies of porphyrin dimer/TiO2-based photocatalyst

In this research, we synthesized a novel panchromatic absorption dimer porphyrin and designed a dimer molecule with maximum absorption in the visible and NIR regions. The work was followed and monitored by its photocatalytic function with anatase TiO2 and brookite-rutile TiO2, and preliminarily compared and tested its photocatalytic disinfection of gram-negative bacteria Escherichia coli (E. coli) in visible light conditions toward the potential of future studies. The finding results were compared with the bare anatase TiO2 and brookite-rutile TiO2. The prepared structure of molecules was confirmed by SEM, EDS, XRD, XPS, and solid-state diffuse reflectance spectral studies.

Mechanochemical synthesis of a novel eutectic of the antimicrobial nitazoxanide with improved dissolution performance

Background: Nitazoxanide (NTZ) is a broad spectrum antimicrobial agent with poor aqueous solubility and low bioavailability. Thus, the generation of new solid forms of NTZ is relevant to improve its unfavorable properties. The present study deals with the application of mechanochemistry for the preparation of alternate solid forms of NTZ, using saccharine (SAC) as coformer. Methods: NTZ-SAC mixtures were prepared by neat and liquid-assisted grinding (LAG) and characterized using differential scanning calorimetry (DSC), hot stage microscopy (HSM), X-ray Powder Diffraction (XRPD), 13C Solid-state Nuclear Magnetic Resonance (SSNMR) and Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. Powder dissolution (PD) profiles were obtained with USP apparatus 2 in buffer phosphate pH 6.5 with 0.25% Tween 80 - 0.25% triethanolamine and in 0.25% sodium lauryl sulfate, at 37 ºC ± 0.5 ºC and 75 rpm. Drug release was characterized in terms of dissolution efficiency (DE). Results: XRPD, SSNMR and DRIFT indicated that NTZ and SAC did not cocrystallize but DSC and HSM revealed that they formed a binary eutectic mixture which melted near 176 °C, a melting temperature lower than those of NTZ and SAC. PD data indicated that the 1:1 NTZ-SAC sample obtained by LAG exhibited a slightly higher DE than pure NTZ in the two assayed media. Conclusion: NTZ and SAC formed a eutectic, the first reported for this drug, which improved its dissolution rate and opened the pathway for studies searching for new eutectics with better biopharmaceutical attributes than NTZ and the NTZ-SAC eutectic reported herein.

A lanthanide–mercury compound: preparation and photophysical properties

A neodymium (Nd)–mercury (Hg) complex [Nd(IA)2(H2O)3(NO3)(HgCl2)] n ·2nH2O·nEtOH (1; IA is isonicotinic acid anion) was synthesised and characterised. Compound 1 is of monoclinic system, space group C2/c with a = 25.4224(12), b = 8.1410(3), c = 22.2963(9) Å, β = 90.788(4)°, V = 4614.1(3) Å3, C14H24Cl2HgN3NdO13, Z = 8, M r = 858.09, D c = 2.471 g/cm3, S = 1.120, μ(Mo Kα) = 9.174 mm−1, F(000) = 3256, R = 0.0530 and wR = 0.1288. The mercury (II) (Hg2+) ions are bound by two terminal chloride (Cl−) ions and two nitrogen (N) atoms, displaying a distorted tetrahedral geometry. The neodymium (III) (Nd3+) ion is coordinated with nine oxygen (O) atoms to form a monocapped square antiprismatic polyhedron. Every two neighbouring neodymium (III) ions are interlinked by two μ 3-bridging IA groups to form a one-dimensional (1D) infinite –Nd–IA2–Nd– chain. The 1D chains link to each other through HgCl2N2 tetrahedra and yield a two-dimensional layer. It emits cyan photoluminescence, which should be due to the 4 G 11/2 → 4 I 9/2 transition of the 4f electrons of the neodymium ions. It exhibits Commission Internationale de l’Éclairage chromaticity coordinates of (0.1274, 0.3525). A solid-state diffuse reflectance spectrum unveils that it has a 2.51 eV band gap.