Correlated Color Temperature Values Research Articles

The impact of varied correlated color temperatures on visual comfort in museum exhibitions: integrating physiological and subjective assessments

ABSTRACT Correlated Color Temperature (CCT) significantly influences mood, comfort, and potentially overall health. However, its impact on visitors’ visual experience in museum design remains insufficiently explored. This study aims to investigate the effects of different CCT settings (3000 K, 4500 K, 6000 K) on visual comfort within a simulated museum space. Using 3D modeling and physiological recordings, 200 participants assessed visual comfort. Consistent findings support that a CCT of 4500 K provides the highest comfort level, aligning with the observed trend in eye gaze duration. Pupil diameter variability indicates that greater comfort is associated with higher CCT values. While differences in heart rate variability (HRV) were not statistically significant, there is a tendency for HRV to increase with longer fixation durations. These findings challenge literature advocating for lower CCT values in museum lighting, emphasizing the need to balance conservation and visitor experience. This study provides empirical evidence supporting the optimization of visual comfort in museum lighting design through a CCT value of 4500 K, offering valuable insights for practitioners. However, limitations include potential scene disturbance and the simulated environment. Future studies should diversify samples and explore a broader range of CCT values.

1,1,1-Trifluoro-5,5-dimethyl-2,4-hexanedione based ternary complexes of Eu(III): Synthesis, structural and luminescence investigations

In this current study, we have synthesized four europium(III) complexes utilizing a tri-fluorinated β-diketone moiety: 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione (TFDH) with auxiliary ligand: 2,2′- bipyridine and its derivatives. FTIR, UV–Vis and luminescence spectroscopic characterizations were implemented for evaluation of the bonding and luminous characteristics in synthesized europium(III) complexes. Eight-coordination environment around Eu3+ ion has been demonstrated by 1H NMR spectral data. Photoluminescence (PL) study of these complexes has been carried out in powdered form. Characteristic red emitting behavior of Eu(III) ion was observed corresponds to the transition of 5D0→7F2 in PL spectra of Eu(III) complexes. The CIE (Commission Internationale de l'Eclairage) chroma coordinates 1931 and CCT (Correlated Color Temperature) values were derived from the information obtained from the emission spectra. The Judd-Ofelt intensity parameters (Ωτ) and excited state deactivation time (τ) in solid state have also been estimated. In the synthesized Eu(III) complexes, the europium ion was present in a highly polarizable ligand field, as demonstrated by the higher values of Ω2. Values of band gap i.e. optical and electronic as well as the red luminous nature of prepared complexes showed up their utilization in display devices.

Enhanced photocatalytic, photoluminescence and fingerprint properties of Dy3+ ions doped BaZrO3 nanopowders for multifunctional applications

In the present investigation photoluminescent, photocatalytic and advanced forensic applications of hydrothermally prepared BaZrO3:Dy3+ (1–9 mol%) nanopowders were studied in detail. Fresh green Aloe Vera (AV) gel was used as capping agent for the preparation of NPs. The pure cubic phase was observed by powder X-ray diffraction (PXRD) profiles. Fourier transform infrared (FTIR) was utilized to investigate the functional groups present in the prepared NPs. The modification in surface morphology was investigated by using Field emission scanning electron microscope (FESEM) images. The grain size was evaluated by utilizing transmission electron microscope (TEM) images and found to be around 48 nm. Further, with the help of high-resolution TEM (HR-TEM) images the interplanar distance was calculated and found to be 0.32 nm. Photoluminescence (PL) studies were carried out in detail using excitation and emission spectra. The maximum intensity was detected for peak 388 nm ascribed to 6H15/2 → 4I13/2 + 4F7/2 of Dy3+ transition under 574 nm emanation wavelength. The obtained emanation spectra consist of 3 characteristics peaks of Dy3+ ions at 480, 574 and 666 nm attributed to 4F9/2→ 6H15/2, 4F9/2→ 6H13/2 and 4F9/2→ 6H11/2 respectively. The PL intensity increases up to 7 mol% dopant ion weight and afterwards it decreases due to concentration quenching phenomena. The dipole–dipole interaction was responsible for this quenching. The color coordinates results in white emission witnessed from the Commission International de I'Eclairage (CIE) and correlated color temperature (CCT) diagrams. The average CCT value was observed around 4836 K. Further, the color purity (CP) and external quantum efficiency (QE) was estimated and found to be 86 % and 64 % respectively. The photocatalytic degradation activity was also studied for the prepared powders and found that, the optimum degradation was observed till 180 min. The kinetics studies revealed that, the present powders were in agreement with the 0th order with estimated ko = 0.015 with R2 value of 0.98 respectively. The powders were also explored for their latent fingerprint (LFP) visualization on various porous and non-porous surfaces and found that, the powders exhibited all types of fingerprint ridge details including the 3rd type such as sweat pores and scar. The observed all outcomes specify that, the prepared powders can be used as a potential candidate for the fabrication of white LEDs (wLEDs), excellent photocatalyst and fingerprint visualization.

Novel Sm3+-doped La3Ga5MO14 (M = Si or Ge) phosphors for indoor illumination: effects of M cations on photoluminescence.

A series of La3(1-x)Ga5MO14:xSm3+ (M = Si or Ge) orange-red phosphors with high color purity, low correlated color temperature, and good thermal stability were successfully synthesized via a high-temperature solid-phase technique. The phase structure and morphology of La3Ga5SiO14(LGSi):xSm3+ and La3Ga5GeO14(LGGe):xSm3+ were investigated. Sm3+-doped LGSi and LGGe phosphors emitted orange-red light under an excitation of 403 nm, and the optimal doping concentrations were 3 mol% and 2 mol% with excellent color purities of 98.46% and 98.25%, respectively. The concentration quenching mechanism of both the samples was dominated by dipole-dipole interaction, and the effect of Si4+ and Ge4+ on luminescence performance was discussed. The internal quantum efficiencies of LGSi:0.03Sm3+ and LGGe:0.02Sm3+ were calculated to be 27.14% and 56.07%, respectively. The CIE and CCT values indicated that the luminescence of the prepared phosphors was in the orange-red region. Additionally, a white light-emitting diode (w-LED) was fabricated with LGGe:0.02Sm3+ phosphors, which was capable of emitting bright and warm white light and exhibiting a high color rendering index (CRI) of 87.17 and an appropriate correlated color temperature (CCT) of 6108 K. These results indicated that the prepared phosphors with excellent luminescent performances have potential application in indoor illumination.

The dual-model up/down-conversion green luminescence of NaSrGd(MoO4)3: Er3+ and its application for temperature sensing.

Er3+-doped phosphors are widely used as dual-functional optical thermometers due to their distinctive up/down-conversion luminescence and the thermally coupled energy states (2H11/2 and 4S3/2) of Er3+. The development of high-performance Er3+-activated optical thermometers is both an intriguing subject and a formidable challenge in the field. This article investigates the up/down-conversion (UC and DC) photoluminescence properties of NaSrGd(MoO4)3 (NSGM): Er3+. When excited at 375 and 975 nm, the phosphors emit peaks at 530, 550, and 657 nm, corresponding to the 2H11/2, 4S3/2, and 4F9/2 → 4I15/2 transitions of Er3+, with the 4S3/2 → 4I15/2 transition displaying the highest intensity. The optical properties are comprehensively studied through UV-visible absorption, PL spectroscopy, and PLE spectroscopy. Optimal luminescence intensity is achieved at an Er3+ concentration of 4% mol. The resulting chromatic coordinates (x, y) and high correlated color temperature (CCT) values of the doped phosphors yield thermally stable cold emissions in the green region, boasting color purities of approximately 98.76% and 80.74% for DC and UC conversion, respectively. The optical temperature sensing properties of thermally coupled energetic states are explored based on the fluorescence intensity ratio principle. NSGM: 0.04Er3+, under 375 nm light excitation, demonstrates the maximum relative sensitivity of 0.87%/K-1 at 298.15 K, spanning a wide temperature range from 298.15 to 488.15 K. Conversely, under 975 nm light excitation, NSGM: 0.04Er3+ exhibits the maximum relative sensitivity of 0.63%/K-1 over the same temperature range, with temperature uncertainty (δT) less than 0.50 K and repeatability (R) (more than 98%). These findings position this material as a promising candidate for optical thermometer applications. The optical heating capacity of the synthesised phosphor is also determined using optical thermometry results, and heat generation up to approximately 457 K is found, indicating that NSGM: 0.04Er3+ could be useful for photo-thermal therapy.

Dual emission quaternary alloyed quantum dots for white light-emitting diodes with high color-rendering index

We report the synthesis of manganese doped Ag–Zn–In–S(AZIS)/ZnS QDs for the facile fabrication of white light-emitting diodes (WLEDs). By controlling the ratio of Mn/(Zn + In), dual emission Mn:AZIS/ZnS QDs with different relative proportion of host emission and Mn2+-related emission were prepared. With proper doping, the emission of Mn: AZIS/ZnS QDs covers most of the visible spectrum. Based on the as prepared Mn:AZIS/ZnS QDs, a warm WLED device exhibited a highest color rendering index (CRI) of 92.5 companied by a correlated color temperature (CCT) of 3162 K. With the increasing of Mn2+ concentration, the corresponding WLED devices shown warmer CCT values and lower luminous efficiencies (LEs). The color-conversion efficiency of the QDs decreasing with the increasing of Mn2+ concentration may be responsible partly for the variation of device LEs. With further deep investigation on the mechanism of color-conversion between the exciting light and QDs, and the energy transfer from the host material to the manganese dopant, WLEDs based on the dual emission Mn:AZIS/ZnS QDs with better device performances are excepted to find diverse application in lighting fields.

Synthesis and luminescence characterization of Dy3+/Sm3+ Co-doped Y2MgTiO6 double-perovskite phosphors for warm WLED

Y2MgTiO6:Dy3+/Sm3+ double-perovskite phosphors were synthesized using the high-temperature solid-state reaction method, and their luminescence properties were examined through various techniques, including Rietveld refinement, excitation and emission spectra, Commission Internationale de l'Eclairage (CIE) analysis, and band gap simulation. Ab initio calculations were performed to analyze the band gap and density of states, allowing for the prediction of the effect of Dy3+ and Sm3+ doping on emission intensity. The emission spectra of Y2MgTiO6 (YMTO) doped with Sm3+ and Dy3+ exhibited maximum peaks at 602 nm and 575 nm, respectively, when excited at 325 nm. Both YMTO:Sm3+ and YMTO:Dy3+ demonstrated excellent thermal stability. The CIE coordinates of YMTO doped with 1 mol% Dy3+ were determined to be (0.3771, 0.3804), with a correlated color temperature (CCT) of 4115 K, confirming its suitability for warm white light applications. Introducing 1 mol% and 3 mol% of Sm3+ ions into the Dy3+/Sm3+ co-doped YMTO allowed for adjustable CCT values of 3719 K and 3302 K, respectively, further enhancing their potential for use in warm white light-emitting diodes (WLEDs).

Realization of orange-red emitting double perovskite structured Sm3+-doped Ba2ZnWO6 nanophosphors: A systematic study of structural, photoluminescence and photometric properties for solid-state lighting applications

Exploring luminescent materials that meet the necessary specifications which can beneficial for solid-state lighting applications has prompted extensive research. In this context, the present article deals with a successful exploration of orange-red emanating double perovskite structured Sm3+ (1–11 mol %) -doped Ba2ZnWO6 nanophosphors synthesized via a self-igniting solution combustion route. The crystallographic studies of the phosphors confirm the cubic phase having Fm̅3m space group. The morphological investigations exhibit non-uniform flaky-type particles with agglomeration. The average optical energy gap of the phosphors is found to be around 3.25 eV. The photoluminescence emission spectra enclosed three distinctive peaks located at around 564, 597, and 644 nm, which are attributed to 4G5/2→6HJ (J = 5/2, 7/2 and 9/2) transitions of Sm3+ ions, respectively. The estimated chroma coordinates (0.5385, 0.4527) are located in the orange-red region of the chromaticity diagram and achieve correlated color temperature values between 1865 and 2783 K with color purity in the range 94.7–98.7 %. The obtained results dominantly certified the suitability of the prepared nanophosphors as a favorable candidate for solid-state lighting applications.

Colour-tunable and warm white light emitting thermally stable Dy3+/Sm3+ co-activated tungstate-tellurite glasses for photonic applications

Transparent single Dy3+, Sm3+, and Dy3+/Sm3+ co-activated tungstate-tellurite (TWKZBi) glass matrices were synthesized via melt-quenching process. The optical features of the prepared glass matrices were examined with the aid of the absorption spectra. Under various excitation wavelengths (366, 388 and 454 nm), Dy3+ doped TWKZBi (TWKZBiDy) glasses revealed a prevailing emission peak ⁓575 nm related to the yellow band (4F9/2 → 6H13/2) transition, while Sm3+ doped TWKZBi (TWKZBiSm) glass matrices reveal strong intense emission peak at ∼600 nm associated with the orange-red band (4G5/2 → 6H7/2) transition. The emission intensity progressively surges with an increment in Sm3+ ion content (up to 1.5 mol%), confirming the ET mechanism between Dy3+ and Sm3+ ions. Application of Dexter's ET formulation with the Reisfeld's approximation revealed that the ET mechanism involves a non-radiative dipole-dipole (d-d) interaction between Dy3+ and Sm3+ ions. The average lifetime (τavg) values for the 4F9/2 state of Dy3+ ions in the TWKZBiDySm glass sample was measured and found that these values decreased with increasing Sm3+ ion content. In addition, the ET efficiencies (ηDy→Sm) of the TWKZBiDySm glass matrices were evaluated using the lifetime curves. The color coordinates (x, y) and the correlated color temperature (CCT) values of the co-activated glass samples were estimated. Based on the chromaticity coordinates and CCT values, it was found that the desired color of the TWKZBiDySm glass samples can be modulated from warm white light to orange-red light via precisely adjusting the concentration of Sm3+ ions and at selected excitation wavelengths. Furthermore, the emission intensity observed at 373 K was 83.83 % compared to the emission intensity at ambient temperature, indicating the excellent thermal stability of the TWKZBiDySm glasses prepared. The above results confirm that the prepared Dy3+/Sm3+ co-activated TWKZBi glass matrix can be a promising candidate for white light and other photonic devices.

Structural and luminescence studies on thermally stable Bi3+‐activated Ba3MoTiO8 phosphors for near UV‐pumped w‐LED applications

AbstractThis research presents the outcomes of diverse morphological and photoluminescence (PL) studies performed on Bi3+ ion–doped Ba3MoTiO8 phosphors prepared via the conventional solid‐state reaction method. Phase assessment was carried out via the X‐ray diffraction (XRD) studies. Field emission scanning microscopy (FE‐SEM) and energy‐dispersive X‐ray analysis (EDAX) have been used to study the surface morphology anda elemental composition. Fourier transform infrared spectroscopy (FT‐IR) was used to study the character and vibrational frequencies of bonds in the phosphor lattice. Room‐temperature PL was performed under 275 and 386 nm excitations, displaying a broad band in the blue region corresponding to the 3P1 → 1S0 transition of Bi3+ ions. The Commission Internationale de L'Eclairage coordinates and correlated color temperature values show that the as‐prepared phosphors emit in the blue vicinity. The decay curves under both excitation wavelengths show a single exponential behavior. Temperature‐dependent PL studies confirmed the high thermal stability of the phosphor. We want to endorse these phosphors as a blue‐emitting component in white light‐emitting diodes (w‐LEDs) and solid‐state lighting (SSL) applications.

Structure and tunable white-light emission of the Ce3+/Dy3+ co-doped MgO–K2O–B2O3–P2O5 borophosphate glasses by modulating Mg/K ratio

In this work, the Ce3+/Dy3+ co-doped MgO–K2O–B2O3–P2O5 borophosphate glasses were successfully fabricated by the melt-quenching technique. The structure and optical characteristics were investigated using XRD, DSC, FTIR, Raman spectra, transmittance spectra and photoluminescence (PL) spectra. With increasing Mg/K ratio, the free oxygen introduced by MgO as its contents increase facilitated the conversion of [BO3] triangular units to the denser [BO4] tetrahedral units. The phonon energy of the glass system was estimated to be about 1020 cm−1 from the Raman spectra. Spectroscopic analysis revealed the energy transfer (ET) between Ce3+ and Dy3+ may exist, and the ET between Ce3+ and Dy3+ was explored in detail. Under 315 and 349 nm excitation, the PL spectra disclosed three distinct emission peaks at about 370, 484, and 575 nm, which corresponded to the 5d-4f (Ce3+), 4F9/2 → 6H15/2 (Dy3+), and 4F9/2 → 6H13/2 transitions (Dy3+), respectively. The blue shift in the peak position of the cerium ions within the excitation and emission spectra was associated with the decrease in the overall optical basicity of the glass caused by compositional modulation. Tunable white light emission can be achieved by varying the excitation wavelength. Under 349 nm excitation, the optimum chromaticity coordinate (0.325, 0.333) with a correlated color temperature value of 5856 K is obtained at the Mg/K ratio of 3:2, which points to the Ce3+/Dy3+ co-doped MgO–K2O–B2O3–P2O5 borophosphate glasses are a prospective fluorescent material for exploitation of white light-emitting diodes (WLEDs).

Recommended Method for Determining the Correlated Color Temperature and Distance from the Planckian Locus of a Light Source

ABSTRACT Correlated color temperature (CCT) is one of the primary metrics used to characterize the visual appearance of light and is most informative when coupled with distance from the Planckian locus (Duv). Given a set of chromaticity coordinates—which are calculated from a light source’s spectral power distribution—it is possible to compute CCT and Duv with varying levels of accuracy. Over the last six decades at least a dozen methods have been proposed to compute CCT while balancing accuracy with calculation complexity. CCT values become inconsistent at some level of precision when calculated using different methods, which in turn can lead to discrepancies in dependent or subsequent calculations used by lighting professionals and may be problematic in software. Although methods are now documented that can provide extremely high accuracy, no consensus body has recommended a preferred method. This analysis examines both the calculation speed and the CCT and Duv accuracy of previously proposed and new methods. With consideration of the calculation accuracy, computational burden, calculation complexity, and considerations of practical implementation, we recommend a recent modification of the Robertson method.

Effective role of Co-dopants (Dy3+, Sm3+) on Tunable multicolour emission of Tb3+ doped telluroborate glasses for Natural White light applications

In the current work the efficacy of incorporation of Dy3+ and Sm3+ ions into Tb3+ doped new telluroborate glass as well as their interactions was investigated. In this study, Tb3+ ions were employed as activators and sensitizers for both Dy3+ and Sm3+ ions emissions, which emanate from the excited states of Dy3+ (4F9/2) and Sm3+ (4G5/2) ions through a non-radiative energy transfer process. To validate the emission gamut of the prepared glasses, distinct emission colours were inspected with the CIE 1931 chromaticity analysis and the appropriate correlated colour temperature (CCT) values were estimated. The emission decay profile relating to the Tb3+ ions (5D4 state) of the glasses was investigated. The energy transfer efficiency, which stems from Tb3+ ion to Dy3+ and Sm3+ ions were found to be 49 and 54% respectively. The IH model was successfully used to analyse the interaction mechanism.

Effect of alkali/alkaline modifiers on Pr3+ ions doped lead boro-tellurite glasses for lasing material applications

Pr3+ incorporated Lead boro-tellurite glasses were prepared and their structural and optical performance was explored through absorption, luminescence and decay measurements. The oscillator strengths deliberated from the absorption spectral features were used to estimate the Judd-Ofelt (J-O) intensity parameters. The emission spectral features recorded monitoring an excitation at 610 nm exhibits two intense peaks located at 496 nm; 3P0 → 3H4 transition pertains to blue emission and similarly at 543 nm; 3P1 →3H5 transition refers to green emission. Radiative parameters for the 3P0 → 3H4, 3P0→3H5 and 3P0 →3F2 transitions are evaluated and the modifications observed by changing the alkali/alkaline modifiers on the Lead boro-tellurite glasses were reported. The glasses lie in the province of intense blue & green emission is observed through CIE diagram. Especially glasses with higher correlated color temperature values mainly used for roads covered with fog and also for tunnel lighting purposes. Radiative parameters consequent to the salient emission bands elucidate the aptness of the glass materials for the manufacture of photonic equipment's. Decay studies explored the non-exponential behaviour. It is concluded that, modifiers activated Pr3+ doped oxide and oxy fluoride incorporated glass system is aptly appropriate for optoelectronic gadget applications.

Synthesis and luminescent properties of Eu(III)/Tb(III) rare earth complex-coated the core-shell structured silica microspheres: Unleashing the potential for white light emission

A rare earth organic complex, SiO2@ATPA-Si-RE (RE = Eu, Tb), exhibiting a core-shell structure, was synthesized using the ligand (HOOC)2C6H3NHCONH(CH2)3Si(OCH2CH3)3(ATPA-Si) to connect the silica microspheres core and coordinate with rare earth ions. The pH value of the reaction was adjusted to produce organic complex shells with thicknesses of 2.0 nm and 5.0 nm, while the SiO2 core measured a diameter of 125 nm. Luminescence spectra indicated that the emission intensity of the SiO2@ATPA-Si-RE (RE = Eu, Tb) core-shell structure was stronger than that of the ATPA-Si-RE organic complex due to a perfect match between the triplet energy level of SiO2@ATPA-Si and the excited energy level of rare earth ions (Eu3+, Tb3+). Remarkably, the core-shell structure with a 2.0 nm shell thickness possessed a greater emission intensity compared to the 5.0 nm shell thickness. Moreover, these findings unveiled the tunability of luminescence color, ranging from green or red to white, by adjusting the doping ratio of Eu3+ and Tb3+ ions and the coating thickness of complexes. Particularly, a warm white light emission, characterized by CIE coordinates (0.389, 0.347), a color rendering index value of 86.7, and a low correlated color temperature value of 3550 K, was achieved using the organic complex with a 2.0 nm thickness coated on SiO2 microspheres with a doping ratio of Eu3+ at 0.7 mmol and Tb3+ at 0.3 mmol. Conversely, the complexes with a 5.0 nm coating thickness and Tb3+ doping ratio of 0.3 mmol yielded a cold white light emission. These findings demonstrate the potential applications in next-generation lighting industry and display systems.

Luminescence studies of high color purity red-emitting [formula omitted] phosphor prepared by microwave-assisted synthesis technique

A set of red-emitting phosphor materials (Ca1−xAl4O7:Eux3+, x = 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13) were synthesized through microwave-assisted combustion synthesis for the first time. The crystal structures and phase purity of Eu3+ ions-activated calcium dialuminate (CaAl4O7) phosphor were investigated by XRD study and Rietveld refinement analysis were performed. The prepared phosphors exhibit monoclinic crystal structure having C2/c space group. From the radius difference percentage calculation, the occupancy of Eu3+ ions in Ca2+ sites was confirmed which is in better harmony with the refinement result. Morphological analysis was investigated through SEM study. Structural characteristics and the presence of the functional groups were analysed though FTIR study. The optical band gap (Eg) was determined to be 5.46 eV by studying the UV–VIS reflectance spectra. PL measurements were carried out for the prepared material to study the luminescent behaviour. The presence of charge transfer band was observed in the excitation spectra. It is found that the prepared phosphor materials exhibits emission rich in red at 611 nm with fixed excitation wavelength at 393 nm. The concentration quenching and energy transfer kinetics were analysed by employing Blasse and Dexter’s formula that attributed the non-radiative energy transfer to the dipole-dipole (d-d) interactions. Local site symmetry was analysed to study the symmetry of the environment in the neighbourhood of Eu3+ ions in the host matrix. To analyse the colorimetric performance of the phosphor materials, the correlated color temperature (CCT), color purity were calculated by using the CIE chromaticity co-ordinates (CIE 1931). The calculated CCT value shows the appearance of the emitted color of the phosphor in the warmer region. CaAl4O7:Eu3+ phosphor manifests high color purity which was found to be 97.39 %. The PL decay time measurement were performed for Ca1−xAl4O7:Eux3+ (x = 0.07) phosphor to obtain the decay lifetime. The estimated decay time (1.44 ms) indicates that the prepared phosphor material has a good potency to be utilized as a red-emitting phosphor for wLED, display technology and other applications.

A Hybrid Mobile Application for Quality Grade of Tobacco (Nicotiana tabacum L.) Using Correlated Color Temperature

Concerning tobacco (Nicotiana tabacum L.) producers the size and color of the leaf are important factors in understanding the quality grade of tobacco leaves in the market. The color of tobacco leaves serves as an indicator of quality and is referred to as the maturity index when determining the optimal time for harvesting. In this study, a hybrid mobile application was developed to help determine the harvest time. CoLab was preferred as the backend. Python Imaging Library (Pillow) was used for image processing on the server side. Color correction was performed on the images taken with the help of X-rite. The correlated color temperature (CCT) value of the repaired images was calculated. The CCT values were calculated using the Ohno method. Quality grade (QG) was calculated using the mean CCT value. The data of the images obtained depending on the time were used in the application as a graphic. We present quality grade of tobacco automatically identifying the plant leaves in a given image with the help of the mobile application.

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.

Excellent photoluminescence and electrochemical properties of Sm3+ doped Ca2MgSi2O7 nanophosphor: Display and electrochemical sensor applications

A series of orange-red light emitting Ca2MgSi2O7:Sm3+ nanopowders were fabricated via low-cost eco-friendly green combustion technique using Aloe vera gel as fuel. The phase purity of the samples were confirmed by the powder X-ray diffraction (PXRD) technique. Pure single-phase tetragonal structure is observed from the PXRD results with no additional impurity peaks. The band gap energy of the fabricated powders was estimated by diffuse reflectance spectra (DRS) and is found to be in the range of 4.01–5.98 eV. A high resolution scanning electron microscope (SEM) was used to study the morphological behaviour of the samples. Honeycomb-like structures are observed from the SEM results. The particle size was evaluated by transmission electron microscopy (TEM) and is found to be ∼50 nm. The interplanar distance is found to be 0.53 nm. Photoluminescence properties were systematically studied in detail. The phosphors are successfully excited at 403 nm NUV light, producing reddish-orange characteristic emission. The emission peaks are centered at 558 (4G5/2 → 6H5/2), 607 (4G5/2 → 6H7/2) and 645 nm (4G5/2 → 6H9/2), respectively. Among the observed peaks the red emanation (4G5/2 → 6H7/2) is stronger than the orange emission (4G5/2 → 6H5/2) in the current investigation. The photoluminescent concentration quenching is noticed above 5 mol% Sm3+ ion doping content. The dipole–dipole interaction resulting in cross relaxation is found to be the principal cause of concentration quenching mechanism. The color features such as Commission Internationale de l’Eclairage (CIE) and correlated color temperature (CCT) were studied in detail. The optimized chromaticity coordinates were estimated to be (0.6363, 0.3632), which fall in the reddish-orange region. The average CCT value obtained is 3362 K. The average color purity is found to be ∼82%. Sm3+ incorporated Ca2MgSi2O7 samples are possible contender for single white light generation commercial candidates owing to their strong hypersensitivity of Sm3+ ions through host, least possibility for re-absorption of blue-green emission owing to poor direct f–f excitation of Sm3+ ions, and high color purity (reddish-orange emission). The prepared powders exhibit excellent electrochemical redox properties and CPE modified optimized powders show outstanding sensitive response which indicates its use in the potential electrochemical sensor materials for drug sensing studies.

Designing and Judd-Ofelt evaluation of versatile luminescent Eu (III) complexes sensitized with β-diketone ligand for multifarious applications.

The present research work entails synthesis of one binary and four ternary red light emitting Eu (III) based complexes with 3-benzylidene-2,4-pentanedione as main ligand and 1,10-phenanthroline, bathophenanthroline, neocuproine and 4,4'-dimethyl-2,2'-bipyridyl as auxiliary ligands. The Metal-Organic framework of the series was elucidated using EDAX, elemental analysis, FT-IR and 1 H-NMR. This Eu (III) series exhibit optimum thermal stability making them a promising candidate for OLED's. On the basis of emission spectra their optical parameters such as non-radiative and radiative decay rate, luminescence decay time, intrinsic quantum efficiency and Judd-Ofelt intensity parameter were determined. The mono-centric luminescence and Judd-Ofelt parameters reveals the non-existence of symmetry around the europium center. CIE chromaticity coordinates, CCT values, color purity and asymmetric ratios authenticate the color coordinates of complexes in red region. Optical band gap values lies within wide band gap semiconductors range revealing their utilization in military radars, biological labeling.