Commission Internationale d'Eclairage Research Articles

Modification of Local Site Preference for Achieving Tunable Color Emission from Blue to Near-White in Sr3(PO4)2:Dy3+ Phosphor

The color tunability of Sr3(PO4)2:1%Dy3+ phosphor from blue to near white is studied at various annealing conditions. Higher temperature annealing promotes agglomerated rhombohedral (α) phase formation. Experimental and theoretical analysis reveal dopant preference at the low-symmetry Sr(II) site, altering electric (4F9/2→6H13/2) and magnetic (4F9/2→6H15/2) dipole transitions, thereby affecting the yellow-to-blue (Y/B) ratio. The luminescence intensity variation and color tunability are explained based on the local site symmetry and occupation probability of the dopant in the host lattice. An increase in the luminescence intensity up to an annealing temperature of 1200 °C, followed by quenching is observed due to the oxygen vacancies. Commission Internationale d'Eclairage (CIE) color coordinates of (0.31, 0.38), Correlated Color Temperature (CCT) of 6341 K, and color purity of 22.57% confirm the potential of Sr3(PO4)2:1%Dy3+ phosphor annealed at (1200 °C, 6 hrs) for white light generation. A probable photoluminescence mechanism involving 4f→5d→4f transitions in Sr3(PO4)2:1%Dy3+ is proposed.

Natural Pigments-Based Two-Component White Light Emitting Systems.

In this paper, a new class of two component white light emitting systems viz, JaB (java plum + beetroot) {I}, and CaB (carrot + beetroot) {II} were developed through resonance energy transfer (RET) phenomenon by using a fruit (java plum) and two vegetable (carrot and beetroot) extracts. In these white light emitting systems, java plum and carrot are the donors while beetroot is the acceptor. The primary fluorescent pigments present in the natural extracts (i.e., anthocyanin in java plum, β-carotene in carrot, and betanin in beetroot) were responsible for the white light emission. The CIE (Commission Internationale d'Eclairage) coordinates for I and II were {0.32, 0.34} and {0.33, 0.33}, respectively, in solution phase. Interestingly, the white light emission (WLE) was also achieved in agar-agar gel medium. In gel medium, the CIE values were {0.31, 0.34} and {0.33, 0.32} for I and II, respectively. The donor-acceptor distance (r) for I and II were found to be 0.5 and 0.4nm, respectively. Furthermore, the rate of energy transfer was also quantified with the values of 2.78 × 109s-1 for JaB (I) and 1.02 × 108s-1 for CaB (II) systems. The mechanistic investigation of the two white light systems was further supported by DFT studies.

Vivid-Colored Electrorheological fluids with simultaneous enhancements in color clarity and Electro-Responsivity

HypothesisSurface modification of dielectric materials changes the dipole–dipole interactions under electric fields, thereby controlling the electrorheological (ER) response. The introduction of metal oxides onto mica templates and further coating of dyes is expected to simultaneously improve the color clarity and ER performance. ExperimentsDye-coated TiO2 platelets on mica are synthesized for high-performance colorful ER fluids. A sol–gel method is utilized to grow TiO2 on mica to prepare precursor light-colored mica/TiO2 materials, which are coated with appropriate dyes to enhance the vividness as determined by the Commission Internationale de clairage L*a*b* color system. The color expression and color clarity improvement are explained via the light interference effect and the presence of chromophores. FindingsThe uniform TiO2 layers can be obtained under low pH conditions with controlled nucleation kinetics. The addition of dyes to TiO2 increases the surface area and porosity of ER materials and introduces heteroatoms that act as positive factors. In practical ER applications, dye-coated TiO2-based ER fluids exhibit higher ER performances compared with the corresponding light-colored TiO2-based ER fluids. The vivid-colored ER fluids could provide an easy selection for a wide range of rheological systems requiring a specific magnitude of stress by confirming the color.

A facile and efficient preparation method for the doped light emitting layer in OLEDs: Blade-coated planar source evaporation

Although vacuum thermal evaporation (VTE) is a widely-used fabrication method in organic light-emitting diodes (OLED) industry, it has long been suffering from the sophisticated fabrication process, low material utilization, and high costs, which become much significant in the preparation of doped light emitting layer (EML). To overcome those intrinsic drawbacks of VTE, we propose a facile and efficient preparation method for the doped EML, i.e., blade-coated planar source evaporation (BCPSE), which combines the benefits of both solution-based blade-coating and combined planar source evaporation (BCPSE) techniques. BCPSE can simplify the fabrication process, increase the material utilization, and reduce the fabrication time, without degrading the device performance compared to that prepared by VTE. The film morphology and fabrication condition were carefully investigated and optimized, which show that BCPSE can increase the material utilization to 95 % and decrease the preparation time to several seconds, implying a great reduction in the fabrication cost. The validity of BCPSE was further demonstrated in a comparison study of a typical orange phosphorescent OLED, in which the mixed ternary EML comprising iridium-based dopant, n-type host, and p-type host was fabricated by using both VTE and BCPSE techniques. With the BCPSE technique, the device exhibited improved maximum external quantum efficiency (EQEmax) of 7.9 %, maximum current efficiency (CEmax) of 13.7 cd/A, and maximum power efficiency (PEmax) of 12.0 lm/W, which are comparable to the device employing VTE. In addition, both techniques gave the same electroluminescent spectra with the Commission International d'Eclairage (CIE) coordinates of (0.59, 0.38). The proposed method is not only helpful in reducing the fabrication costs while maintaining the device performance, but promising in advanced OLED applications, such as microOLEDs.

Efficient and stable green organic light-emitting diode utilizing an asymmetric butterfly-shaped chromophore with enhanced reverse intersystem crossing and suppressed exciton annihilation

Intermolecular electron-exchange interactions involving long-lived triplet state excitons dominate the quenching process of the films. In this work, a butterfly-shaped thermally activated delayed fluorescence (TADF) emitter 10,10′-(5-((3,5-di(9H-carbazol-9-yl)phenyl)sulfonyl)-1,3-phenylene)bis(9,9-dimethyl-9,10-dihydroacridine) (BCZ-DPS-BAD) with diphenylsulfone skeleton is constructed by modulating the rigid steric hindrance on the electron donor fragment to weaken intermolecular electron-exchange interactions. Analysis of the ground and excited state properties, crystal structure, steady-state and transient photophysical characteristics reveals that BCZ-DPS-BAD exhibits loose intermolecular arrangements with no direct facing close packing and weak π–π interactions of 4.18 Å and 4.67 Å. The triplet state excitons can swiftly return to the single exciton state in accordance with a short delayed fluorescence lifetime (2.3 μs) and a quick reverse intersystem crossing rate (1.85 × 106 s−1), obstructing the way for the triplet state to lose energy. A remarkable maximum external quantum efficiency of 21.8 %, maximum current efficiency of 56.8 cd/A and exciton utilization rate of 82 % is achieved for BCZ-DPS-BAD-based green non-doped OLED, concomitant with Commission Internationale d'Eclairage (CIE) coordinates of (0.30, 0.50). Notably, BCZ-DPS-BAD behaves stable non-doped OLED performance with efficiency roll-off of 4 % at 1000 cd m−2.

White light emission from fluorescent ionic liquids in the solution and gel forms using RGB system

A single blend of red, green, and blue (RGB) chromophores made of organic molecules is of greater significance in the evolution of inexpensive, metal-free, color-tunable white light emission (WLE). In this paper, three ionic liquid-based compounds viz. [TPA-SB][Br], [PTZ-SB][Br], and RhB-IL were designed for the effective generation of white light in the solution state with the Commission Internationale d’Eclairage (CIE) coordinates of (0.33, 0.33). The mechanism of WLE involves Förster resonance energy transfer (FRET) with simultaneous emissions, as confirmed by several mechanistic investigations, including PL titration, spectrum overlap, Forster distance calculations and fluorescence lifetime experiment. Moreover, this novel mixture was immobilized in gelatin gel to obtain WLE in gel phase with a CIE of (0.33, 0.31). Furthermore, the gel was applied as a coating on a UV LED to reveal its applicability as an affordable organic coating for WLE by simultaneous emission. Notably, this is the first report on the emanation of white light from simple ionic liquid system via Forster resonance energy transfer.

Reaction-time-controlled carbon dots nanoarchitectonics with stable and bright photoluminescence for white light emission

It is still a challenge for multicolor carbon dots (CDs) with stable and bright photoluminescence (PL). The controlling of synthesis becomes a hot topic. In this paper, CDs with blue-, green- and red-emitting named as B-CDs, G-CDs, and R-CDs were prepared using three isomers of phenylenediamine as precursors by one-step solvothermal synthesis. Green and red emitting CDs with C, N and O components named as samples G-CDs and R-CDs revealed uniform nanoparticle distribution with average sizes of 7.2 and 5.7 nm, respectively. The PL peak wavelength of three kinds of CDs were 430, 546 and 613 nm, and their average fluorescence lifetime was 5.32, 22.35, 8.74 ns, respectively. The full width at half maximum of PL spectra of the samples was 65.12, 92.63, 83.62 nm, and their PL quantum yields were 8.19, 43.43, and 5.14%, respectively. The brightly luminescent CDs were further embedded in prepared polyvinyl alcohol films to prepare a white emitting layer by adjusting the ratios of CDs with different emitting color. The composite CDs revealed stable and bright white emitting in the film with a Commission Internationale d'Eclairage (CIE) coordinate of (0.28, 0.33). The result suggested that these unique luminescent CDs have potential applications in various luminescence fields.

Tunable White Light Emission of a Metal-Organic Framework Based on a Bisquinoxaline Derivative by Introducing Red-Green Cationic Dyes.

The unique structural advantages give metal-organic frameworks (MOFs) a special use as host substrates to encapsulate organic dyes, which would result in specific host-guest composites for white-light phosphors. In this work, an anionic MOF exhibiting blue emission was constructed using bisquinoxaline derivatives as photoactive centers, which could effectively encapsulate rhodamine B (Rh B) and acriflavine (AF) to form an In-MOF ⊃ Rh B/AF composite. By simply adjusting the amount of Rh B and AF, the emitting color of the resulting composite could be easily adjusted. The formed In-MOF ⊃ Rh B/AF composite exhibits broadband white light emission with ideal Commission International ed'Eclairage (CIE) coordinates of (0.34, 0.35), a color rendering index of 80.8, and a moderately correlated color temperature value of 5193.96 K. This strategy can be easily extended to other blue-emitting MOFs and dyes, thus opening up new prospects for the development of white-light-emitting materials.

Luminescence characteristics of Dy3+ doped sodium alumina borate glass: Role of silver

Metallic nanoparticle (NP) doped glasses have been studied as promising candidates for various technological applications due to their ability to improve the luminescence properties of rare earth ions. In this work, Dy2O3 and Ag2O co-doped sodium alumina borate glasses were synthesized by conventional melt-quenching technique. Raman analysis verified the existence of [BO3] and [BO4] groups with B–O stretching vibrations in the prepared glasses. Transmission electron microscope images confirmed the presence of spherical Ag NPs, whose average diameter is about 7.60 nm, in H-0.5Dy1Ag glass matrix. The optical and luminescence properties were investigated according to Ag concentrations. The negative value of the bonding parameters, calculated from the absorption spectra, indicates the ionic nature between the Dy3+ ions and its surrounding ligands. In order to determine the nature of the Dy-O bond and the symmetry around the Dy3+ ion environment, Judd–Ofelt intensity parameters (Ω λ, λ = 2, 4, 6) were obtained from the absorption spectra. The luminescence spectra obtained under 350 nm excitation exhibits four emission bands at 481 (4F9/2→6H15/2), 572 (4F9/2→6H13/2), 662 (4F9/2→6H11/2), and 750 (4F9/2→6H9/2) nm. The intensity of emission spectra increases with Ag2O content until 1.0 wt% in H-0.5Dy-yAg glasses and then decreases due to the back-energy transfer (ET) from Dy3+ to Ag+. The ET mechanism from Ag+ to Dy3+ ion for H-1Ag-xDy glasses were investigated through Forster-Dexter’s theory and were found to be quadrupole-quadrupole type. The various radiative properties were calculated by using Judd-Ofelt intensity parameters and emission spectra. It was found that the 572 nm emission band, located in the yellow region, has higher radiative parameters. As a function of Ag concentration, the Y/B values, Commission Internationale d’Eclairage (CIE) chromaticity coordinates (x,y) and correlated color temperatures (CCT) were evaluated. The CIE chromaticity coordinates and CCT values of all glasses are located in the white light region. The decay time values of 1S0→3D1 transition of Ag+ ions and 4F9/2→6H13/2 transition of Dy3+ ions confirm the ET from Ag+ to Dy3+ ions. Overall, the present study indicates that the synthesized glasses with Ag addition exhibits improved luminescence, making them potential candidate for white LEDs.

Strong red emission in double perovskite Sr3LiSbO6: Eu3+ phosphor with high color purity for solid-state lighting applications

Intense red-emitting double perovskite Sr3LiSbO6 (SLSO) phosphor materials have been prepared by doping of Eu3+ rare earth ion using the facile solid-state reaction route. The obtained results displayed the hexagonal structure of the sample, having space group R3c. Diffuse reflectance spectra also reflected the 3.42eV optical band gap of SLSO: 2%Eu3+ which was less than that of the pure SLSO (3.5eV), consequently showing the negative Burstein Moss effect. Photoluminescence (PL) emission spectra showed a concentration quenching effect beyond the 2mol% of Eu3+ doping concentration, indicating the involvement of dipole-dipole interaction. The lifetime of the prepared phosphor was estimated by the PL decay curve; with an average decay time of 808.6 μs. Photometric studies revealed the required lesser correlated color temperature (CCT) values (<1900K) with high color purity (CP) of 99% and Commission International de’Eclairage (CIE) coordinates were located around the red region. Drawn results demonstrated that the proposed phosphor could be a promising strong red-emitting phosphor for the white light-emitting diode (wLED) based on ultra-violet UV or blue chip.

Mercaptopropionic acid-assisted synthesis of green and blue emissive copper nanoclusters for multimodal sensing, logic gate, and white light applications

A time-controlled synthesis strategy for luminescent copper nanoclusters (CuNCs) was adopted via a two-step process. First, non-emissive copper nanoparticles (CuNPs) were formed by reducing copper salt with ascorbic acid (AA), and then the CuNPs were converted into green (G-CuNCs, λem = 520 nm) and blue emissive CuNCs (B–CuNCs, λem = 440 nm) after time-controlled treatment (2 h and 43 h) with mercaptopropionic acid (MPA). Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis unambiguously demonstrate the etching of CuNPs with the reduction of core size (from 6.09 nm for CuNPs to 2.67 nm and 1.92 nm for G-CuNCs and B–CuNCs, respectively) and a simultaneous lowering of the contribution of the +2 oxidation state of Cu species. Moreover, B–CuNCs showed selectivity and sensitivity towards Fe3+ and glutathione (GSH) via fluorescence (Fl) turn-off-on mechanism; the limit of detections (LODs) for respective analytes were 6.2 nM and 281 nM. The Fl turn-off mechanism by Fe3+ involves both static and dynamic quenching processes, whereas restoration of the Fl intensity of B–CuNCs was triggered by the GSH-induced reduction of Fe3+ to Fe2+ and subsequent release of Fe3+ from the surface of B–CuNCs. A logic gate was constructed based on the Fl response of the B–CuNCs toward the analytes. Finally, the synthesized B–CuNCs and G-CuNCs were employed for white light emission (WLE) with Commission Internationale d'Eclairage (CIE) coordinates of (0.33, 0.32) with the aid of another red-emitting GSH-capped gold nanocluster (GSH-AuNCs).

Combustion Synthesis and Photoluminescence Study of Sr3Y1-x(BO3)3: xPr3+ (0.01 ? x ? 0.05) Red Borate Phosphor for Near Blue Pumped WLED

Abstract: A red borate phosphor Sr3Y1-x(BO3)3: xPr3+ ( 0.01 ≤ x ≤ 0.05 ) was prepared by using a solution combustion reaction method, and its photoluminescence property is investigated. The synthesized phosphors were characterized by X-ray diffraction (XRD), scanned electron microscope (SEM) and photoluminescence (PL). Their excitation bands at 375, 384 and 395 nm are originated from the transitions of 3H4→3P2, 3H4→3P1 and 3H4→3P0 of Pr3+ ion. Under375nm nm excitations, the emission of Pr3+ at 595, 614 and 632 nm are attributed to 1D2→3H5, 3P0→3H6 and 3P0→3F2. The Commission International de Eclairage (CIE) chromaticity coordinates are (X = 0.67745889, Y = 0.322362077) for Sr3Y1-x(BO3)3: xPr3+ . The result shows that Sr3Y1-x(BO3)3: xPr3+ is promising candidate for red phosphors in the fabrication of pc-WLED and in blue LED chip WLED.

Encapsulating Organic Dyes in Metal–Organic Frameworks for Color-Tunable and High-Efficiency White-Light-Emitting Properties

The design of white-light phosphor is highly desirable for practical applications in SSL (solid-state lighting) and its related fields. Dye-loaded metal-organic frameworks (MOFs) have been widely demonstrated as one type of promising down conversion materials for WLEDs (white-light-emitting diodes), but two issues (dye leakage and inadequate quantum efficiency) require to be addressed before possible applications. Here, a series of single-phase dyes@In-MOF phosphors have been prepared in two different ways: the in-situ process and soaking method. The study of these dyes@In-MOF phosphors confirms the importance of this in-situ process that could effectively increase dye loading and quantum efficiency and greatly decrease dye leakage. As a result, a perfect WLED, fabricated using the in-situ-synthesized (AF/RhB@In-MOF)-3 (AF: Acriflavine; RhB: Rhodamine B) and 450 nm blue LED chip, exhibited a very high quantum yield (QY, up to 42.27%), a high luminous efficacy (LE) of 50.75 lm/W, a high color rendering index (CRI) of 91.2, and nearly identical Commission International ed'Eclairage (CIE) coordinates (0.33,0.31), indicating the potential application of the dye-loaded MOFs with good color quality in smart white LEDs.

Resonant energy transfer between plasmonic silver and biomolecule for colour tuning and white light emission

A simple eco-friendly method was employed to generate white light using pomegranate-PVA - curcumin mediated silver nanoparticles (CAg NP-PVA) mixture. The white light emission is obtained by integrating the green emitting curcumin and blue emitting pomegranate extract. Controlling the emission of curcumin with Ag NP-PVA and mixing with pomegranate extract resulted in efficient white light with the Commission Internationale d’Eclairage (CIE) chromaticity coordinate (0.28,0.31). Ag NP-PVA and anthocyanin played a significant role in obtaining CIE coordinate close to that of pure white light (0.33,0.33). The optimized white light emission obtained from pomegranate- CAg NP-PVA mixture is cheap and fairly green in nature.

Understanding the effect of meat electrical conductivity on Pulsed Electric Field (PEF) process parameters and the ability of PEF to enhance the quality and shorten sous vide processing for beef short ribs

The aim of this research was to investigate how the electrical conductivity of short ribs affected Pulsed Electric Field (PEF) process parameters and the ability of PEF to enhance their quality and reduce sous vide (SV) processing time. Short ribs with different range of electrical conductivity (3–6, 6–9, and 9–12 mS/cm) values were treated using input voltage of 10 kV, pulse width of 20 µs, pulse frequency of 50 Hz and pulse number, of either 1600 (low intensity PEF/LPEF) or 5200 (high intensity PEF/HPEF), followed by SV processing at 60 °C for either 24 or 36 h. The quality parameters assessed were cooking loss (%), Texture Profile Analysis (TPA) parameters, and Commission Internationale d’Eclairage (CIE) L*a*b* colour parameters. There was a variation in electrical conductivity of short ribs according to the position of the bone in the short rib, which demonstrated good congruence with the distribution of fat and connective tissue. SV processing with or without PEF pre-treatment did not have a significant effect (p > 0.05) on cooking loss or CIE L*a*b* colour parameters. Short ribs with a medium conductivity (6–9 mS/cm) had a significantly lower hardness after high intensity PEF followed by SV for 24 h, whilst short ribs with an average conductivity of 3–6 and 9–12 mS/cm required longer SV time (up to 36 h) and had a significantly lower hardness compared to non PEF pre-treated samples. TPA values of short ribs treated with the same PEF intensity and SV processing parameters were comparable regardless of the short ribs initial electrical conductivity, which indicates that PEF treatment could ameliorate the biological electrochemical variability inherent to short ribs and PEF could be the potential tool to decrease their SV processing time and enhance their tenderness.

Conjugated Polymers-Based Ternary Hybrid toward Unique Photophysical Properties.

The improvement of optical and optoelectronic properties of the individual poly [2-methoxy-5- (2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene]–End capped with Dimethyl phenyl (OC1C10–PPV–DMP), and poly (9,9′-di- n -octylfluorenyl-2,7-diyl) (F8) was revealed by blending them in ternary hybrid with optimal ratio (F8/2 wt.% MEH-PPV/2 wt.% OC1C10–PPV–DMP). All individual and optimal ternary solutions were prepared via the solution-blending method followed by depositing them onto glass and ITO substrates using spin-coating technique. The semi-crystalline phase of the ternary hybrid and the strong mixing between the conjugated polymers were evidenced by observing the X-ray diffraction patterns that related to F8 into the hybrid diffractogram. The optical and optoelectronic properties of all prepared thin films were investigated in terms of absorption and emission spectra, Commission International d′Eclairage (CIE) coordinates, and current–voltage (I-V) characterizations. Emission peaks at the entire range of visible spectrum can be revealed from the ternary hybrid of the three individual conjugated polymers, producing white emission as evidenced from the emission spectrum and CIE coordinates of the hybrid. Among all fabricated organic light-emitting diodes (OLEDs) devices, the ternary hybrid-based-OLED revealed the best performance in terms of current and turn-on voltage.

Luminescence of Macrocyclic Mononuclear DyIII Complexes and Their Immobilization on Functionalized Silicon-Based Surfaces.

Two mononuclear DyIII complexes, [Dy(L1)(NCS)3] (Dy-EDA) and [Dy(L2)(NCS)3] (Dy-DAP), where Ln (n = 1-2) corresponds to a macrocyclic ligand derived from 2,6-pyridinedicarboxaldehyde and ethylenediamine (L1) and 1,3-diaminepropane (L2) were immobilized on functionalized silicon-based surfaces. This was achieved by the microcontact printing (μCP) technique, generating patterns on a functionalized surface via covalent bond formation through the auxiliary -NCS ligands present in the macrocyclic complex species. With this strategy, it was possible to control the position of the immobilized molecules on the surface. Water contact angle measurements, X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectra (IRRAS), and atomic force microscopy (AFM) confirmed that the surfaces were successfully functionalized. Furthermore, the optical properties in a broad temperature range were investigated for the as-prepared compounds. At room temperature, Dy-EDA was shown to emit in the deep blue region (Commission Internationald'Eclairage (CIE): (0.175, 0.128)), while Dy-DAP in the white region (CIE: (0.252, 0.312)). The different CIE values were due to the contribution of the strong emission of the ligand in the case of Dy-EDA. Besides, surface photoluminescence measurements showed that the immobilized complexes retained their bulk emissive properties.

Color coordination of emerald on CIE color space based on first-principles calculations

Be3Al2(SiO3)6 including Cr3+ known as emerald have been widely studied and utilized for solid-state laser materials. Numerous theoretical investigations on these systems have also been published in the literature since the electronic energy levels, optical properties, and structures of Cr3+ impurities in emerald systems have been thoroughly investigated using a variety of experimental approaches. In general, semi-empirical computations have been used to accomplish the majority of theoretical interpretations of experimental data. Although in the case of non-empirical calculations, the agreement between theoretical and experimental optical properties was improved by taking into account the energy corrections, quantitative evaluation of the color of emitted light was not feasible until recently. Here, the color coordinates of emerald under the standard illuminant has been calculated to perform a quantitative evaluation based on the optical spectra. The “theoretical” color was calculated and presented visually on the Commission Internationale d’Eclairage (CIE) color space based on the theoretical spectra obtained non-empirically using the so-called first-principles discrete variational multi-electron method, known as DVME. The absorption spectra of emerald were calculated using CrO69− model cluster with D3 symmetry. Several key effects in reproducing optical spectra were investigated in detail, such as lattice relaxation, energy correction, and orbital effects. The accuracy of this approach in predicting absorption spectra was analyzed thoroughly under various computational conditions. The results show that accounting for all of the above effects is important to producing the absorption spectra. Specifically, enlarging the considered orbital in the calculation improved the agreement between the computed and experimentally-observed colors. This study is crucial for validating the non-empirical calculations made using the DVME approach to assess the color of emitted light quantitatively.

Assessing of photoluminescence and structural properties of Dy+3 doped cadmium tantalate phosphor

According to the charge balance, trivalent dysprosium doped Cdx-1Ta2O6:xDy3+ (x=0.5, 1, 2, 3, 5) phosphor series was fabricated by solid state reaction route at 1100 C for 8 h. The synthesized phosphors were investigated by XRD (X-ray diffraction), SEM (scanning electron microscopy), and PL (photoluminescence) analyses. XRD and SEM analyzes revealed the orthorhombic colombite crystal structure and the presence of oval-like and shapeless morphology with submicron and several micron grain sizes, respectively. With the excitation of 387.8 nm, the phosphors exhibited blue and yellow emissions at 482.4 nm and 578.5 nm depending on the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+, respectively. The concentration quenching did not occur because the improvement in the charge balance reduced the structural defects and decreased the conversion of excitation energy to non-radiative transitions. The emission intensity of cadmium tantalate phosphor increased with increasing Dy3+ ion concentration up to x=5 value, and did not occurred the concentration quenching which reduces emission intensity. The Commission Internationale d’Eclairage (CIE) coordinates of Cdx-1Ta2O6:xDy3+ (x=0.5, 1, 2, 3, 5) phosphors were found near the white region in the chromaticity diagram

Self-quenching-resistant fluorescent tunable sulfur quantum dots

Fluorescence-tunable sulfur quantum dots (SQDs) were obtained by an assembly-fission process and assisted etching with H2O2. The morphological and structural characterization indicated that the obtained SQDs possess excellent dispersion, high water solubility and abundant surface functional groups, which is beneficial to its further application. In the Gaussian software, the electron cloud density distribution around the entire molecular structure is simulated and the density generalization calculations confirms that the main reason for the red shift of emission is the synergistic effect of SQDs size and surface states. Moreover, blue fluorescent SQDs (B-SQDs) showed high sensitivity and specific selectivity toward berberine hydrochloride with detection limits as low as 0.24 nM, and have been successfully used for water sample and actual drug detection. It is noteworthy that the solid-state luminescence properties of SQDs are mainly attributed to the adsorption of chain PEG on the surface of SQDs. By mixing SQDs with epoxy resin, dual-color fluorescent films were prepared and used as the fluorescence conversion layer to manufacture high-performance light-emitting diodes. The CIE (Commission Internationale d′Eclairage) coordinates of WLED is (0.27,0.29), CCT (Correlated color temperature) is 5793 K and CRI (Color rendering index) is 85.2. Moreover, the prepared SQDs are highly fluorescent and enable latent fingerprint imaging for identity recognition. This work has advanced the development of SQDs for analytical sensing, optical devices, and fingerprint imaging.