Spectroscopic,mechanical and magnetic characterization of some bismuth borate glasses containing gadolinium ions

The ultrasonic parameters, the optical parameters along with the IR spectroscopy and magnetic susceptibility studies have been employed to explore the role of Gd₂O₃ in the structure of the glasses xGd₂O₃–60B₂O₃–10MoO₃–(30-x)Bi₂O₃, with 0 ≤ x ≤ 7 mol %. IR analysis indicates that Gd₂O₃ is preferentially incorporated into the borate network-forming BO₄ units. It is assumed that Bi₂O₃ and MoO₃ enter the structure as modifiers in the form of BiO₆ and MoO₆ only. The compositional dependence of the mechanical and the optical parameters are interpreted in terms of the transformation of the structural units BO₃ into BO₄, the increase in the number of bridging oxygen atoms, and the substitution of high bond strength Gd–O, in the place of low bond strength Bi–O bond. The results of the magnetic susceptibility reveal the paramagnetic behavior as described by the Curie-Weiss law and indicating the presence of weak antiferromagnetic exchange interactions between Gd³⁺ ions. The magnetic entropy change of the glasses was determined according to the temperature and magnetic field dependence of magnetization.     

Analysis of Dopant Atom Distribution and Quantification of Oxygen Vacancies on Individual Gd‐Doped CeO2 Nanocrystals

This work reports the analysis of the distribution of Gd atoms and the quantification of O vacancies applied to individual CeO₂ and Gd‐doped CeO₂ nanocrystals by electron energy‐loss spectroscopy. The concentration of O vacancies measured on the undoped system (6.3±2.6 %) matches the expected value given the typical Ce³⁺ content previously reported for CeO₂ nanoparticles. The doped nanoparticles have an uneven distribution of dopant atoms and an atypical amount of O vacant sites (37.7±4.1 %). The measured decrease of the O content induced by Gd doping cannot be explained solely by the charge balance including Ce³⁺ and Gd³⁺ ions.     

XAFS characterization of La1−xSrxMnO3±δ catalysts prepared by Pechini’s method

XAFS experiments at the Mn and Sr K-edges were carried out in order to investigate the short-range arrangement of Mn and Sr sites on La_1−xSr_xMnO_3±δ highly doped perovskites (x = 0, 0.2, 0.4 and 0.6). The Mn K-edge EXAFS spectra show a static Jahn–Teller distortion of the MnO₆ for x = 0 and 0.2, which is drastically reduced as x increases. The distortion of perovskite, characterized by the Mn–O–Mn tilt angle, progressively decreases with increasing Sr contents. Sr K-edge results indicated a decrease on the Sr–Mn coordination number upon Sr doping. Based on this and TPD results, a charge compensating mechanism is proposed suggesting a partial Mn oxidation and formation of Mn defect vacancies due to the introduction of Sr.     

Optical absorption and EPR spectroscopic studies of (30 − x)Li2O–xK2O–10CdO–59B2O3–1Fe2O3: An evidence for mixed alkali effect

Optical absorption and EPR spectroscopic studies were carried on (30 ? x)Li₂O–xK₂O–10CdO–59B₂O₃–1Fe₂O₃ (x = 0–30) glass system to understand the effect of progressive doping of Li⁺ ion with K⁺ ion. Optical absorption results show typical spectra of Fe³⁺ ions and the various optical parameters such as, optical band gap, Urbach energy, oxide ion polarizability, optical basicity and interaction parameter were evaluated from the experimental data. The observed optical band gap and Urbach energy values show large deviation from the linearity where as the other parameters show small deviation from the linearity with the progressive substitution of Li⁺ ions with K⁺ ions. The observed EPR spectra are representative of Fe³⁺ ion in octahedral and axial fields in the glass network. The number of paramagnetic centers and paramagnetic susceptibility values were evaluated at different resonance lines for all the specimens and these parameters show non-additive nature with the progressive substitution of Li⁺ ions with K⁺ ions in the glass network. This is first ever observation of mixed alkali effect (MAE) in EPR and optical parameters of mixed alkali borate glasses.     

Fine tuning bifunctional properties of Y0.5Gd0.5BO3 by doping with Ce3+ and co-doping with Li+,Ca2+ and Al3+ following an epoxide mediated gel approach

Realizing the ubiquitous presence of rare-earth orthoborates in various applications involving their optical properties, the current investigation is directed towards the exploration of epoxide mediated rapid synthesis to make YBO₃. Highly crystalline orthoborate with disordered vaterite structure resulted on calcining xerogel from the reaction of yttrium chloride, boric acid and propylene oxide at 900 °C as verified from diffraction, vibration spectroscopic and microscopic techniques. Following this approach, orthoborate containing 50 mol% of Y and Gd was obtained and characterized. Dissolution limit of Ce³⁺ in Y_0.50Gd_0.50BO₃ has been determined. Cerium doping resulted in the reduction in the optical band gap of these samples and appended photocatalytic ability in terms of degradation of aqueous rhodamine-6G (Rh-6G) dye solution. The intensity of 4f → 5d transition of Ce³⁺ increased monotonously with increase in cerium content. The role of distortion on the blue emission from Ce³⁺ and photocatalytic properties of these samples were comprehended by characterizing Li⁺, Ca²⁺ and Al³⁺-doped samples (up to 10 mol%) for yttrium. The distortion of Y_0.50?xM_xGd_0.45Ce_0.05BO₃ lattice decreased in the order, R_Ca2+ > R_Y3+ > R_Li+ > R_Al3+, with the emission intensity (5d → 4f transitions) from Ce³⁺ increasing in the reverse order. Optical band gap was found to decrease for the Li⁺, Ca²⁺ and Al³⁺ doped samples as compared to undoped one. These doped samples retained their catalytic ability as verified from their use in the photo degradation of rhodamine-B (Rh-B) dye. An insight in to possible mechanism operative in the present photo catalytic degradation experiments has been attempted by carrying out trapping experiments.     

Spectroscopic properties of RBiBO4 (R = Ca,Sr) glasses doped with TiO2

Transparent glasses, melt quenching derived, containing 10RO·20Bi₂O₃·(70 ? x)B₂O₃·xTiO₂ [R = Ca, Sr] with x = 0, 0.5, 1.0 wt% were characterized by X-ray powder diffraction. Physical and spectroscopic properties viz., density, absorption, emission, electron paramagnetic resonance (EPR) and FTIR were investigated. The absorption band around 823 nm in pure glass samples is attributed to the electronic transition of ³P₀ to ³P₂ of Bi⁺ radicals. A small absorption hump centered around 609 nm is found in all doped glasses due to ²T_2g to ²E_g transition of octahedral Ti³⁺ ions. The emission results revealed that all the samples exhibit a broad emission band covering entire visible-light range, with λ_ex = 360 nm, centered 470–520 nm corresponds to electronic transition of ³P₁ to ¹S₀ of Bi³⁺ ions, therefore the present materials can be potentially used as tunable or full-color display systems. And a strong emission around 706 nm with λ_ex = 514 nm due to transition of ²P_3/2 to ²P_1/2 of Bi²⁺ ions. In SrO mixed glasses Ti⁴⁺ ions effect the environment of Bi³⁺ ion symmetry units from C₂ to C_3i. A small EPR signal (at room temperature) is observed in titanium doped glasses due to Ti³⁺ ions. In both the series with increase of TiO₂ concentration BO₄ units are gradually converted into BO₃ units and new cross linkages are formed, like B–O–Ti, Bi–O–Ti at the expense of B–O–B bonds.     

On the sol–gel preparation of different tungstates and molybdates

The preparation and characterization of the M′–M′′–O nitrate–tartrate (M′ = Ca, Ba, Gd and M′ = W, Mo) precursor gels synthesized by simple, inexpensive, and environmentally benign aqueous sol–gel method is reported. The obtained gels were studied by thermal (TG/DSC) analysis. TG/DSC measurements revealed the possible decomposition pathway of synthesized M′–M′′–O nitrate–tartrate gels. For the synthesis of different metal tungstates and molybdates, the precursor gels were calcined at different temperatures (650, 800, and 900 °C). According to the X-ray diffraction (XRD) analysis data, the crystalline compounds CaMo_1-x W _x O₄ doped with Ce³⁺ ions, BaMo_1-x W _x O₄ doped with Eu³⁺ ions and Gd₂Mo₃O₁₂ were obtained from nitrate–tartrate gels annealed at 650–900 °C temperatures. The XRD data confirmed that the fully crystalline single-phase powellite, scheelite, or Gd₂(MoO₄)₃ structures were formed already at 650 °C. Therefore, the suggested sol–gel method based on the complexation of metal ions with tartaric acid is suitable for the preparation of mixed tungstates–molybdates at relatively low temperature in comparison with solid-state synthesis.     

Approaching compositional limits of perovskite – type oxides and oxynitrides by synthesis of Mg0.25Ca0.65Y0.1Ti(O,N)3, Ca1–xYxZr(O,N)3 (0.1 ≤ x ≤ 0.4), and Sr1–xLaxZr(O,N)3 (0.1 ≤ x ≤ 0.4)

Partial substitution of cations and anions in perovskite-type materials is a powerful way to tune the desired properties. The systematic variation of the cations size, the partial exchange of O²⁻ for N³⁻ and their effect on the size of the optical band gap and the thermal stability was investigated here. The anionic substitution resulted in the formation of the orthorhombic perovskite-type oxynitrides Mg_0.25Ca_0.65Y_0.1Ti(O,N)₃, Ca_1-xY_xZr(O,N)₃, and Sr_1–xLa_xZr(O,N)₃. A two-step synthesis protocol was applied: i) (nano-crystalline) oxide precursors were synthesized by a Pechini method followed by ii) ammonolysis in flowing NH₃ at T = 773 K (Ti) and T = 1273 K (Zr), respectively. High-temperature synthesis of such oxide precursors by solid–state reaction generally resulted in phase separation of the different A-site cations. Changes of the crystal structures were investigated by Rietveld refinements of the powder XRD data, thermal stability by DSC/TG measurements in oxygen atmosphere, oxygen and nitrogen contents by O/N analysis using hot gas extraction technique, and optical band gaps by photoluminescence spectroscopy. By moving from Mg_0.25Ca_0.65Y_0.1Ti(O,N)₃ via Ca_1–xY_xZr(O,N)₃ to Sr_1–xLa_xZr(O,N)₃, the degree of tilting of the octahedral network is reduced, as observed by an increase in the B–X–B angles caused by the simultaneously increasing effective ionic radius of the A-site cation(s). In general, increasing substitution levels on the A-site (Y³⁺ and La³⁺) are accompanied by an enhanced replacement of O²⁻ by N³⁻. In all three systems, this anionic substitution resulted in a reduction of the optical band gap by approximately 1 eV (Ti) and up to 2.1 eV (Zr) compared to the respective oxides. For Mg_0.25Ca_0.65Y_0.1Ti(O,N)₃ an optical band gap of 2.2 eV was observed, appropriate for a solar water splitting photocatalyst. The Zr-based oxynitrides required a by a factor of 2 higher nitrogen contents to significantly reduce the optical band gap and the measured values of 2.9 eV–3.2 eV are larger compared to the Ti-based oxynitride. Bulk thermal stability was revealed up to T = 881 K. In general, the thermal stability decreased with increasing substitution levels due to an increasing deviation from the ideal anionic composition as demonstrated by O/N analysis.     

Structural and optical characterization of sol–gel derived boron doped Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanostructured films

Pure and boron (B) doped iron oxide (Fe₂O₃) nanostructured thin films were prepared by sol–gel spin coating method. The effects of B (0.1, 0.2, 0.5 and 1 %) content on the crystallinity and morphological properties of Fe₂O₃ films were investigated by X-ray diffractometer and atomic force microscopy. X-ray diffraction patterns revealed that the Fe₂O₃ films have a rhombohedral crystalline phase of α-Fe₂O₃ phase (hematite) with nanostructure and their crystallite size (D) is changed from 27 ± 2 to 45 ± 5 nm with B dopant content. The minimum crystallite size value of 27 ± 2 nm was obtained for 0.2 % B doped Fe₂O₃ film. Carrying out UV–VIS absorption study for both doped and undoped films at room temperature, it was realized that allowed optical transitions may be direct or indirect transitions. The direct and indirect energy gap values for pure Fe₂O₃ were obtained to be 2.07 and 1.95 eV, respectively. The optical band gap value of the films was changed with 0.1 % B doping to reach 1.86 eV for direct band gap and 1.66 eV in case of indirect band gap.     

Dual-mode luminescence of Er3+/Yb 3+ codoped LnP0.5V0.5O4 (Ln=Y,Gd, La) for highly sensitive optical nanothermometry

The luminescence properties of 2%Er³⁺/15%Yb³⁺ doped LnP_0.5V_0.5O₄ (LnPVO₄) (Ln = Y, Gd, La) phosphors, synthesized via the traditional citric-assisted Sol gel method, are studied under light excitations of 980 nm and 325 nm to generate the ²H_11/2/⁴S_3/2–⁴I_15/2 transitions via up- and downshifting mechanisms, respectively. The phase purity of the samples was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). We present herein a comparative study of the spectral and temperature sensing properties of LnPVO₄: Er³⁺/Yb³⁺ (Ln = Y, Gd, La) phosphors. The crystal field effects on the up-shifting luminescence and on the thermometric parameters are investigated by the substitution of Er³⁺ ions on Y³⁺, Gd³⁺ or La³⁺ sites in the YPVO₄, GdPVO₄ and LaPVO₄ hosts respectively. Fluorescence intensity ratio (FIR) technique was used to study the temperature sensing behavior of the phosphors. This study showed that downshifting emission gives the highest thermal sensitivities and the greatest thermal resolution compared to downshifting emission. These outcomes indicate that these materials are preferred for use in the luminescence temperature sensing in a down-conversion process to provide the greatest performance.     

Tuning luminescent properties through solid-solution in (Ba1−xSrx)9Sc2Si6O24:Ce3+,Li+

A solid-solution of cerium-substituted alkaline earth scandium silicate phosphors, (Ba_1−xSr_x)₉Sc₂Si₆O₂₄:Ce³⁺,Li⁺ (x = 0, 0.25, 0.50, 0.75, 1), have been prepared by solid-state reaction. The structures, characterized using synchrotron X-ray powder diffraction, show the solid-solution closely follows Vegard's law. The substitution of Sr for Ba results in a decrease of the alkaline earth–oxygen bond distances by more than 0.1 Å at all three crystallographic sites, leading to changes in optical properties. The room temperature photoluminescent measurements show the structure has three excitation peaks corresponding to Ce³⁺ occupying the three independent alkaline earth sites. The emission of (Ba_1−xSr_x)₉Sc₂Si₆O₂₄:Ce³⁺,Li⁺ is red-shifted from the near-UV (λ_max = 384 nm) for x = 0 to blue (λ_max = 402 nm) for x = 1. The red-shifted photoluminescent quantum yield also increases when Sr is substituted for Ba in these compounds.     

Luminescence properties of yttrium gadolinium orthovanadate nanophosphors and efficient energy transfer from VO43− to Sm3+ via Gd3+ ions

In this paper, luminescence properties of orthovanadates, Y_1−x−yGd_xVO₄:ySm³⁺ (where x = 0.05–0.50, y = 0.01–0.05), and the energy transfer mechanism from VO₄³⁻ to Sm³⁺ via Gd³⁺ ions were investigated in detail. X-ray diffraction (XRD) analysis confirmed the crystalline phase for synthesized nanophosphor in a tetragonal structure with I41/amd space group. The average crystallite size estimated from XRD was ∼28 nm. Field-emission scanning electron microscopy coupled with energy dispersive X-ray analysis revealed oval shaped morphology and composition of the nanophosphor, respectively. From high-resolution transmission electron microscopy observations, the particle sizes were found to be in the range 10–80 nm. The photoluminescence studies of Y_0.77Gd_0.20VO₄:0.03Sm³⁺ nanophosphor under 311 nm excitation exhibits dominant emission peak at 598 nm corresponding to ⁴G_5/2 → ⁶H_7/2 transition. The energy transfer occurs from VO₄³⁻ to Sm³⁺ via Gd³⁺ ions was confirmed by applying Dexter and Reisfeld’s theory and Inokuti-Hirayama model. Moreover, the energy transfer efficiencies and probabilities were calculated from the decay curves. Furthermore, Commission Internationale de l’Eclairage (CIE) color coordinate (0.59, 0.37) has been observed to be in the orange-red (598 nm) region for Y_0.77Gd_0.20VO₄:0.03Sm³⁺ nanophosphor. These results perfectly established the suitability of these nanophosphors in improving the efficiency of silicon solar cells, light emitting diodes, semiconductor photophysics, and nanodevices.     

Fluorescence OFF-ON-OFF mechanism for the detection of digoxin,La3+, and epinephrine using bovine serum albumin functionalized molybdenum oxide quantum dots

Herein, we synthesized molybdenum oxide quantum dots using bovine serum albumin as a ligand (BSA-MoO_x QDs) via a simple method. The synthesized fluorescent BSA-MoO_x QDs were stable, and blue fluorescence was noticed upon exposure to UV lamp at 365 nm. When excited at 320 nm, BSA-MoO_x QDs showed an emission peak at 406 nm. Atomic force microscopic images demonstrated that the thickness of BSA layer on the surface of MoO_x QDs is 3.9 ± 1.6 nm. The as-synthesized BSA-MoO_x QDs acted as a sensor for the detection of digoxin, La³⁺, and epinephrine via fluorescence OFF-ON-OFF mechanisms, exhibiting linear ranges of 1–25, 0.125–5, and 0.5–10 μM with lower detection limits of 9.74, 23.08, and 4.58 nM for digoxin, La³⁺, and epinephrine, respectively. This method was successfully demonstrated to be an effective analytical platform for measuring digoxin and epinephrine in pharmaceutical and biofluid samples.     

Structure and magnetic properties of homobinuclear gadolinium (III) complex of isonicotinoyl hydrazone

The crystal structure of [Gd₂(μ-L)₃(H₂O)₂]1.5(NO₃)1.5 (OH)5H₂O (where L is union of N, N-Diisonicotinoyl-2-hydroxy-5-methyl-isophthalaldehyde dihydrazone) has been determined by X-ray diffraction method. The complex crystallizes in the monoclinic system, space group P2₁/c with a=1.6654(3), b=1.6904(3), c=2.8039(6) nm, β=91.30(3), final R factor is 6.3%. The structure consists of [Gd₂(μ-L)₃(H₂O)₂]³⁺ cation, one and a half nitrate and 1.5 hydroxyl anions and five water molecules. Within dinuclear cation, Gd(III)—Gd(III) is bridged by oxygen and nitrogen atoms of the three ligands, resulting in Gd? Gd distance of 0.36353(2) nm. Gd(III) exhibits a distorted 1333 stack coordination environment. Magnetic susceptibility measurements in the temperature range 300–4 K revealed the occurrence of weak antiferromagnetic exchange interaction between two Gd(III) ions with a J value of—0.22, and g of 1.93.     

Correlation of crystal structures with electric field gradients in the fluorite- and pyrochlore-type compounds in the Gd2O3-ZrO2 system

Correlation of crystal structure with electric field gradient (EFG) in the fluorite- and pyrochlore-type compounds in the Gd₂O₃-ZrO₂ system Gd_xZr_1−xO_2−x/2 with 0.18?x?0.62 were investigated by ¹⁵⁵Gd Mössbauer spectroscopy, powder X-ray diffraction and point-charge model (PCM) calculation. An intermediate ordered pyrochlore phase forms for 0.45?x?0.55, sandwiched with a disordered fluorite phase for 0.18?x<0.45 and 0.55<x?0.62. Some ¹⁵⁵Gd Mössbauer parameters, especially the quadrupole coupling constant (e²qQ), were found to exhibit a characteristic maximum around the ideal-pyrochlore Gd₂Zr₂O₇ (x=0.50) composition. The validity of the proposed pyrochlore-based structural model was examined by comparing the experimental values of EFG at the Gd sites with those calculated by the PCM calculations.     

Features of the sol-gel process of formation of nanostructured gadolinium oxide

The process of dehydration of Gd(OH)₃·nH₂O obtained by the sol-gel method from a solution of Gd(NO₃)₃, to Gd₂O₃ in the temperature range of 50–700°C was explored. The hydrogel and Gd₂O₃ structurization is shown to depend on the additives (AF-12 and 2-propanol). The final average particle size of Gd₂O₃ after annealing at 700°C is 20±2 nm, depending on the conditions of the synthesis. The resulting oxide particles are larger than the particles of yttrium oxide Y₂O₃ (17±2) obtained under the same conditions of the process due to the higher basicity of gadolinium and its higher coordination number with respect to the OH groups. This promotes the formation of crystalline phases of Gd(OH)₃ at lower temperature, 50–250°C, while maintaining a favorable structural short-range order in passing through an amorphous state to a crystalline Gd₂O₃.     

X-ray photoelectron spectroscopy-based valence band spectra of passive films on titanium

Titanium (Ti) is always covered by thin passive films. Thus, valence band (VB) spectra, obtained using X-ray photoelectron spectroscopy (XPS), are superpositions of the VB spectra of passive films and that of the metallic Ti substrate. In this study, to obtain the VB spectra only of passive films, angular resolution (for eliminating the substrate Ti contribution) and argon ion sputtering (for removing passive films) were used along with XPS. The passive film on Ti was determined to consist of a very thin TiO₂layer with small amounts of Ti₂O₃, TiO, hydroxyl groups, and water with a thickness of 5.9 nm. The VB spectra of Ti were deconvoluted into four peak components: a peak at ~1 eV, attributed to the Ti metal substrate; a broad peak in the 3–10 eV range, mainly attributed to O 2p (~6 eV) and O 2p-Ti 3d hybridized states (~8 eV), owing to the π (non-bonding) and σ (bonding) orbitals in the passive oxide film; and a peak at ~13 eV, attributed to the 3σ orbital of O 2p as OH⁻or H₂O. The VB region spectrum between approximately 3 and 14 eV from Ti is originating from the passive film on Ti. In particular, characterization of VB spectrum obtained with a takeoff angle of less than 24° is effective to obtain VB spectrum only from the passive film on Ti. The property as n-type semiconductor of the passive film on Ti is probably higher than that of rutile TiO₂ceramics.     

Photoluminescent properties of white-light-emitting Li6Y(BO3)3:Dy3+ phosphor

In this study, lithium yttrium borate (LYBO) phosphor was doped with various concentrations of trivalent dysprosium ions. To produce these phosphors, the raw materials were sintered. The phase conformation, crystallinity, grain size, and overall morphology of the synthesized phosphors were studied with X-ray diffraction and scanning electron microscopy. The optimized LYBO phosphor, i.e., the LYBO phosphor that exhibited the highest X-ray- and ultraviolet (UV)-induced photoluminescent intensities, had a Dy³⁺ concentration of 4 mol%. Photoluminescence analysis showed that this phosphor could be easily excited with near-UV light (300–400 nm). The dominant photoluminescence bands were found in the blue (480 nm) and yellow (577 nm) regions of the visible spectrum. The light yield of the X-ray-induced luminescence of the optimized Li₆Y(BO₃)₃:Dy³⁺ was found to be 66% of that of the commercially available X-ray imaging material, Gd₂O₂S:Tb³⁺ (GOS). The chromaticity coordinates of the Li₆Y(BO₃)₃:Dy³⁺ phosphor were x = 0.34 and y = 0.32, which agree well with achromatic white (x = 0.33, y = 0.33). The results of this study show that the synthesized Li₆Y(BO₃)₃:Dy³⁺ phosphor could be used as X-ray imaging material.     

Enhancement of lithium ion conduction in the cubic rare earth oxide

A new type of lithium ion conducting solid electrolyte based on a cubic rare earth oxide was developed by co-doping LiNO₃ and KNO₃ into a (Gd_1−xNd_x)₂O₃ solid, which possesses large interstitial open spaces within the structure. Among the samples prepared, 0.6(Gd_0.4Nd_0.6)₂O₃–0.16LiNO₃–0.24KNO₃ exhibits the highest lithium ion conductivity of 8.05 × 10⁻² and 1.35 × 10⁻³ S cm⁻¹ at 400 and 100 °C, respectively, which is comparable to that of the LISICON materials. Pure Li⁺ ion conduction was successfully demonstrated by the dc electrolysis method.     

Synthesis,properties and mechanism of photodegradation of core–shell structured upconversion luminescent NaYF4:Yb3+,Er3+@BiOCl

Microspherical bismuth oxychloride (BiOCl) can only utilize ultraviolet (UV) light to promote photocatalytic reactions. To overcome this limitation, a uniform and thin BiOCl nanosheet was synthesized with a particle size of about 200 nm. As results of UV–visible diffuse reflectance spectroscopy showed, the band gap of this nanostructure was reduced to 2.78 eV, indicating that the BiOCl nanosheet could absorb and utilize visible light. Furthermore, the upconversion material NaYF₄ doped with rare earth ions Yb³⁺ and Er³⁺ emitted visible light at 410 nm following excitation with near‐infrared (NIR) light (980 nm), which could be utilized by BiOCl to produce a photocatalytic reaction. To produce a high‐efficiency photocatalyst (NaYF₄:Yb³⁺,Er³⁺@BiOCl), BiOCl‐loaded NaYF₄:Yb³⁺,Er³⁺ was successfully synthesized via a simple two‐step hydrothermal method. The as‐synthesized material was confirmed using X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy as well as other characterizations. The removal ratio of methylene blue by NaYF₄:Yb³⁺,Er³⁺@BiOCl was much higher than that of BiOCl alone. Recycling experiments verified the stability of NaYF₄:Yb³⁺,Er³⁺@BiOCl, which demonstrated excellent adsorption, strong visible‐light absorption and high electron–hole separation efficiency. Such properties are expected to be useful in practical applications, and a further understanding of the NIR‐light‐responsive photocatalytic mechanism of this new catalytic material would be conducive to improving its structural design and function.