Color-tunable Properties Research Articles

Color-tunable graphene quantum dots via one-step nitrogen-induced intramolecular charge transfer for in vivo/vitro aminotransferase fluorescence sensing

Monitoring aspartate aminotransferase (AST) has been demonstrated to be a sensitive sign of liver dysfunction and an essential method for determining the health status of the living body. The quantitative analysis of AST in vivo/vitro is still challenged by complicated processes, expensive equipment, and/or limited sensitivity. A colorimetric assay using multicolored fluorescent nanomaterials holds great promise in vivo/vitro sensing for visual and highly sensitive disease diagnosis. However, achieving a one-step synthesis of multicolored fluorescence (FL) GQDs probe presents challenges. Herein, we successfully designed novel multicolored GQDs with a high quantum yield (QY) of 60.7 % via a simple nitrogen-induced intramolecular charge transfer (ICT) approach. Leveraging the non-toxic and color-tunable properties of N-GQDs, we developed an innovative N-GQDs-based FL test paper for sensitive colorimetric on-site detection of AST, employing the FL colorimetric method based on the transamination reaction. The FL quenching intensity demonstrated an excellent linear relationship with the concentration of AST within the range of 2.0−60.0 U/L, achieving an impressively low limit of detection (LOD) as low as 0.065 U/L. Moreover, the N-GQDs were utilized for AST in vivo detection and FL imaging in living zebrafish, further showcasing their potential in various applications such as liver disease diagnosis, assessment of myocardial damage, and monitoring of drug and toxic poisonings.

Role of Histidine 310 in Amydetes vivianii firefly luciferase pH and metal sensitivities and improvement of its color tuning properties.

Firefly luciferases emit yellow-green light and are pH-sensitive, changing the bioluminescence color to red in the presence of heavy metals, acidic pH and high temperatures. These pH and metal-sensitivities have been recently harnessed for intracellular pH indication and toxic metal biosensing. However, whereas the structure of the pH sensor and the metal binding site, which consists mainly of two salt bridges that close the active site (E311/R337 and H310/E354), has been identified, the specific role of residue H310 in pH and metal sensing is still under debate. The Amydetes vivianii firefly luciferase has one of the lowest pH sensitivities among the group of pH-sensitive firefly luciferases, displaying high bioluminescent activity and special spectral selectivity for cadmium and mercury, which makes it a promising analytical reagent. Using site-directed mutagenesis, we have investigated in detail the role of residue H310 on pH and metal sensitivity in this luciferase. Negatively charged residues at position 310 increase the pH sensitivity and metal sensitivity; H310G considerably increases the size of the cavity, severely impacting the activity, H310R closes the cavity, and H310F considerably decreases both pH and metal sensitivities. However, no substitution completely abolished pH and metal sensitivities. The results indicate that the presence of negatively charged and basic side chains at position 310 is important for pH sensitivity and metals coordination, but not essential, indicating that the remaining side chains of E311 and E354 may still coordinate some metals in this site. Furthermore, a metal binding site search predicted that H310 mutations decrease the affinity mainly for Zn, Ni and Hg but less for Cd, and revealed the possible existence of additional binding sites for Zn, Ni and Hg.

Fabrication of robust and color-tunable luminescent elastomers via the high-functionality crosslinker strategy using vinyl-functionalized conjugated polymers

A straightforward fabrication of luminescent elastomers by using vinyl-functionalized conjugated polymers as crosslinkers is presented in this study. By side-chain engineering on the conjugated polymer, multiple vinyl cross-linking points could be created on a single polymer chain, which crosslink with hydrogen-terminated oligo-hydrosilane via hydrosilylation reaction and subsequently constructs a network with multiple chains bridging two adjacent crosslinkers. Based on this high-functionality crosslinker strategy, the obtained elastomer can be stretched to a large elongation of 570 % before breaking with high tensile strength (0.30 MPa) and toughness (0.83 MJ/m3). By changing the structure of the conjugated polymer or swelling the elastomer in solvents, the emission color is tunable. This work provides a facile strategy to prepare flexible light-emitting devices with robust and color tunable properties.

Dual-band photoluminescence mechanism of magnetic doped two-dimensional (PEA)2PbBr4 single crystals

Mn2+ doping effectively realizes white light emission in three-dimensional lead halide perovskite nanocrystals. Meanwhile, research on Mn-doped two-dimensional layered perovskite single crystal is limited. We report centimeter-scale Mn-doped PEA2PbBr4 (C6H5CH2CH2NH3+ and PEA+) single crystals prepared by a slow evaporation method. Mn2+ dopants mainly act as substitutional doping and exhibit paramagnetic properties in the crystal at low doping density, while interstitial doping of Mn2+ prevails and induces antiferromagnetic characteristics at high doping density. Mn:PEA2PbBr4 single crystals exhibit dual-band chromacity-tunable blue-orange photoluminescence originating from excitons and Mn2+ emission. The negative temperature quenching effect is achieved by Mn-doping defects for the temperature-dependent exciton photoluminescence. Upon testing in the low-pressure vacuum chamber, the Mn2+ peak of the single crystal shows a dramatic shift from 610 to 690 nm. These results indicate that Mn:PEA2PbBr4 single crystal can serve as a potential and promising luminescent device material that achieves color tunable properties by regulating the systematic changes in the intensity ratio of exciton emission and Mn2+ emission, which will be very helpful for exploring the application of perovskite in magneto-optical devices in the future.

First principle study to investigate color tunable properties in Bi3+, Tb3+, and Yb3+ doped GdVO4 phosphor

Gadolinium Vanadate (GdVO4) is a luminescent material widely utilized in the production of blue LEDs, owing to its adjustable optical characteristics. By employing density functional theory (DFT) and the EVGGA method, we investigated the impact of doping on the structural, electrical, and optical properties of GdVO4, focusing on Bi, Tb, and Yb doping. Through optimization of the total energy with respect to the unit cell volume, we determined the relaxed structure's electronic properties using the optimized lattice constant. An in-depth analysis of the electronic density of state (DOS), band structure, and linear optical susceptibility revealed a close correlation between the optical dispersion of dielectric susceptibility and the electronic structure, aligning with experimental observations. The color emissions are obtained under single wavelength excitation due to the high overlapping between the VO4 absorption and the π–π* electron transition of the ligands. These findings offer valuable insights into the characteristics of GdVO4 and its doped derivatives, facilitating the development of more efficient phosphor materials for application in photoluminescence and pc-LEDs.

Color-Tunable Ultralong Organic Phosphorescence: Commercially Available Triphenylmethylamine for UV-Light Response and Anticounterfeiting.

Due to the unclear mechanism and lack of effective design for color-tunable ultralong organic phosphorescence (UOP) in a single-component molecule, the development of new types of single-component UOP materials with color-tunable property remains challenging. Herein, commercially available triphenylmethylamine-based single-component phosphors featuring color-tunablity and ultralong lifetime (0.56 s) are reported. The changed afterglow colors from cyan to orange were observed after different wavelengths of UV excitation. Crystal structure and calculation studies show that multiple emission centers in the aggregated states may be responsible for the color-tunablity. In addition, visual probing of UV light (from 260 to 370 nm) and colorful anti-counterfeiting were conducted. More importantly, UV light ranging from 350 to 370 nm could be detected with the minimal interval of 2 nm. The findings provide a new type of single-component color-tunable UOP materials and shed new light on mechanism and design for such materials.

Energy-transfer phenomenon and color-tunable properties of Ca2Al2SiO7: Dy3+/Eu3+ phosphors

Ca2Al2SiO7 (CAS) doped with Eu3+ and Dy3+ was successfully synthesised with the solid-phase reaction method, in which the sample was sintered at 1,280 °C for one hour. The energy-transfer phenomenon from Dy3+ to Eu3+ was observed in the CAS matrix. The optimal doping concentration of Dy3+ and Eu3+ is 1.5 and 1% mol. In addition, the energy-transfer mechanism, CIE colour coordinate, and CCT colour temperature of CAS/Dy3+/Eu3+ were also presented and discussed.

First-principles study of color-tunable properties in Eu-doped Mg2SnO4 phosphors

The present study investigated the electronic and optical properties of a newly synthesized orange-emitting afterglow phosphor, namely Eu: Mg2SnO4, using the full potential linearized augmented plane wave (FP-LAPW) method. To calculate these properties, the generalized gradient (GGA + U) approximation was employed. The results showed that Eu: Mg2SnO4 exhibited a strong optical response in the visible region, thus highlighting its potential as an excellent candidate for various optoelectronic applications. Notably, the material demonstrated a promising band gap of 2 eV (620 nm), specifically in the orange-emitting afterglow phosphor category, while retaining a 3D structure. These findings suggest that Eu: Mg2SnO4 has promising potential for use in various optoelectronic devices.

Achieving purple light excitable high-efficiency temperature-responsive dual- and single-mode afterglow in carbon dots

Afterglow materials including thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) have inspired extensive attention and research in anti-counterfeiting and sensing application prospects. However, a critical challenge currently remains within this afterglow materials only exhibit single-mode phosphorescence or delayed fluorescence with a persistent luminescence but low quantum yield. In this study, carbon dots composites with long-lived afterglow and ultra-high afterglow quantum yields of 193.5 ms and 35.07% were obtained by embedding the luminescent centers of ciprofloxacin into the formed rigid boric acid matrix by a one-step hydrothermal with purple light as the excitation wavelength. It is worth mentioning that the constructed composites exhibit dual-mode afterglow (DF and RTP) features at room temperature. Moreover, the carbon dots composites have distinctive temperature-responsive color-tunable properties and represent afterglow emission dominated by delayed fluorescence or phosphorescence at different temperatures. Based on the extraordinary temperature sensitivity, a single-mode ultra-long phosphorescence with a lifetime of up to 1.11 s is achieved at low temperatures. Additionally, as-prepared carbon dots composites exhibit the afterglow quantum yield of 40.97% in CB-VII, which is an ultra-high value for inorganic non-metallic materials. Furthermore, the resultant composites of carbon dots with new potential materials of encryption technology are designed for advanced information encryption and anti-counterfeiting applications.

Structural and optical properties of composite phosphor Thx(MoO4)2/Bi2(1-x)Mo2O9; [formula omitted] doped with Ho3+/Yb3+ as a multifunctional materials

Composite phosphor’s, Thx(MoO4)2/Bi2(1-x)Mo2O9:2Ho3+/5Yb3+ have been synthesized cumulatively by facile co-precipitation process in ethylene glycol (EG) medium and subsequently placed for calcinations. Rietveld refinement of XRD patterns and FTIR analysis confirms the phase formation with a systematic variation of individual phases in dual-phase composite system [Th(MoO4)2-Orthorhombic; β-Bi2Mo2O9-Mononclinic]. Phase-dependent UV-Vis absorption of REs ions (Ho3+/Yb3+) has been observed and the difference between the optical bandgap of both phases leads to show the different aspect of the efficacy of optical properties. PL emission spectra of these phosphors show a strong green, relatively weak red and NIR emissions under λexci= 450 nm. The Yb3+ ions in the phosphor act as sensitizer and responsible for commencing the efficient UC emission, which shows nearly identical emission behavior under 980 nm excitation. Drastic changes in emission intensity (UC/DC) are observed with a relative dual-phase variation. Basically, the different crystal field scenarios around REs ions pertaining to both phases are responsible for the changes in emission intensity. The properties like dual-mode emission, phase dependent emission, color tuning properties, make them multifarious, that can be used for biological cell imaging, phototherapy, optical switching, display devices, solar cells, LEDs, etc.

Eu3+ Single-Doped Phosphor with Antithermal Quenching Behavior and Multicolor-Tunable Properties for Luminescence Thermometry

To date, non-contact luminescence thermometry methods based on fluorescence intensity ratio (FIR) technology have been studied extensively. However, designing phosphors with high relative sensitivity (Sr) has become a research hotspot. In this work, Eu3+ single-doped Ca2Sb2O7:Eu3+ phosphors with a high Sr value for dual-emitting-center luminescence thermometry are developed and proposed. The anti-thermal quenching behavior of Eu3+ originating from the energy transfer (ET) of host → Eu3+ is found and proved in the designed phosphors. Interestingly, adjustable color emission from blue to orange can be achieved. Surprisingly, the degree of the anti-thermal quenching behavior of Eu3+ gradually reduces from 240 to 127% as the Eu3+ doping content increases from 0.005 to 0.05 mol, attributed to most Eu3+ being located in the low symmetrical [Ca1O8] dodecahedral site. According to the differentiable responses of the host and Eu3+ to temperature, the maximal Sr value reaches 3.369% K-1 (383 K). Moreover, the ambient temperature can be intuitively predicted by observing the emitting color. Owing to the excellent performance in optical thermometry, color-tunable properties, and outstanding acid and alkali resistance for polydimethylsiloxane (PDMS) films, the developed Eu3+ single-doped Ca2Sb2O7:Eu3+ phosphors are expected to be prospective candidates in luminescence thermometers and LED devices in various conditions.

Vertical stack integration of blue and yellow InGaN micro-LED arrays for display and wavelength division multiplexing visible light communication applications.

In this work, we demonstrated a convenient and reliable method to realize the vertical stack integration of the blue and yellow InGaN micro-LED arrays. The standard white and color-tunable micro-light sources can be achieved by adjusting the current densities injection of the micro-LEDs. The spectra cover violet, standard white, cyan, etc., showing an excellent color-tunable property. And the mixed standard white light can be separated into red-green-blue three primary colors through the color filters to realize full-color micro-LED display with a color gamut of 75% NTSC. Besides, the communication capability of the integrated micro-LED arrays as visible light communication (VLC) transmitters is demonstrated with a maximum total data rate of 2.35 Gbps in the wavelength division multiplexing (WDM) experimental set-up using orthogonal frequency division multiplexing modulation. In addition, a data rate of 250 Mbps is also realized with the standard white light using on-off keying (OOK) modulation. This integrated device shows great potential in full-color micro-LED display, color-tunable micro-light sources, and high-speed WDM VLC multifunctional applications.

Efficient color-tunable room temperature phosphorescence through carbon dot confinement in urea crystals

Color-tunable phosphorescence has received extensive attention in recent years. Herein, a facile approach for the synthesis of carbon dots (CDs) in urea crystals (referred to as uCDs) is reported. Excitation dependence under ambient conditions and multicolor room temperature phosphorescence (RTP), changing from yellow–green (570 nm) to orange (610 nm) at excitation wavelengths of 365 and 460 nm, is observed in the synthesized uCDs. The multicolor emission can be attributed to the existence of multiple emitting centers in the uCDs and it is determined that hydrogen bonding plays a critical role in achieving RTP. High intensity phosphorescence was achieved by external heating of the prepared uCDs@150, which forms a tighter rigid urea matrix and results in an attained lifetime of 281 ms. Based on these unique color-tunable properties, the synthesized uCDs@150 have potential applications in anticounterfeiting and light-emitting diode technologies. This study not only proposes a strategy to prepare photo-stimulated multicolor RTP materials, but also reveals the potential of CDs in exploiting novel optical materials with unique properties.

Construction of novel luminescent thermometers based on dual-emission centers of rare-earth and bismuth ions.

Optical thermometry based on fluorescence intensity ratio (FIR) technology has several advantages for industrial and medical applications such as remote signaling, non-invasiveness, and excellent spatial resolution. Here, an approach to the construction of luminescent thermometers is proposed based on high-temperature solid-state reactions through doping of rare earth (RE) elements (e.g., samarium (Sm3+) or europium (Eu3+)) into Ca2Y0.97Bi0.03SbO6 (CYBS) phosphors. The tuning of the CYBS:Eu3+ and CYBS:Sm3+ ratios in the phosphors provided a wide range of color changes from purplish blue to red and from purplish blue to pink, respectively. The superiority of optical thermometer is validated by higher values of absolute sensitivity (Sa) and relative sensitivity (Sr). As such, both phosphors exhibit excellent temperature sensing performance with Sa/Sr values (at 483K) of 4.945×10-2/0.968×10-2K-1 (CYBS:0.05Eu3+) and 2.964×10-2/0.864×10-2K-1 (CYBS:0.05Sm3+). Thus, RE-doped CYBS materials with color tuning properties and superior temperature sensing performance are recommended for the construction of novel luminescent optical thermometers.

The influence of Zr4+ doping on the structural and photoluminescence properties of LaPO4:Ce3+/Mn2+ phosphors

A series of LaPO4:Ce3+/Mn2+/xZr4+ (LPOCM:xZr4+) (0% ≤ x ≤ 30%) emission-tunable phosphors were synthesized by a cost-efficient co-precipitation method. The samples presented a monoclinic phase structure and a macroscopic rod-like shape. Photoluminescence (PL) and electron paramagnetic resonance spectroscopy were employed, the Zr4+ concentration-dependent excitation, emission, decay time, and energy transfer (Ce3+ → Mn2+) being discussed in detail. Under UV-excitation of Ce3+, typical green-red PL emission is observed for the LPOCM:xZr4+ phosphors, which is attributed to the 4T1(G) → 6A1(S) transition of the Mn2+ ion. The charge compensation strategy achieved the Mn2+ PL-enhancement and color-tuning effect in LPOCM:xZr4+ phosphors. A strong blue emission with color purity of up to 97% is observed in the Ce3+ singly-doped sample. Cold white light emission can be obtained by doping 5% Zr4+ in LPOCM phosphor under UV irradiation. The corresponding CIE 1931 coordinates were inferred to be (0.309, 0.329), close to the standard white emission (0.330, 0.330). The color was tuned towards whitish-orange/red emissions for higher Zr4+ concentrations (15% and 30%). These findings indicate that the charge compensation approach can greatly improve the PL and color-tunable properties of LPOCM:xZr4+ phosphors.

Synthesis of Tunable Fluorescent Imidazole-Fused Heterocycle Dimers.

A short, concise, and one-pot synthesis of imidazo-fused heterocycle dimers with tunable fluorescent properties has been developed. By the first time use of glyoxal dimethyl acetal in the Groebke–Blackburn–Bienaymé (GBB) three-component reaction (3CR), the innovation features a new series of fluorescence-tunable imidazo-fused heterocycle dimers exhibiting a broad substrate scope with good yields. Luminescence studies demonstrate that these GBB-dimers possess color-tunable properties, and their emission colors can be successively changed from blue to green and yellow by easy substituent control.

Structure and luminescence properties of color-tunable phosphor Sr2La3(SiO4)3F:Tb3+,Sm3+

A series of single-phase and color-tunable phosphors Sr2La3(SiO4)3F:0.15Tb3+,xSm3+ (SLSOF:0.15Tb3+,xSm3+) was prepared using solid-state route. The X-ray diffraction (XRD) was used to characterize the phase of the as-prepared samples. The synthesized phosphors have apatite-type structure without other impurities. Sm3+ and Tb3+ ions substitute La3+ into the lattice and form a single-phase solid solution. The elements are evenly distributed in the sample according to the scanning electron microscopy (SEM) results. The crystal structure of the host phosphor was refined by the Rietveld method. The optical properties were studied in detail by investigation of the luminescence and diffuse spectra, fluorescence decay curves and energy transfer efficiency. The phosphor color can be changed from green (0.29, 0.48) to yellow/orange and red (0.57, 0.42) via adjusting the doping ratio of Sm3+. The SLSOF:0.15Tb3+,xSm3+ phosphors can emit typical multicolor light such as green, yellow, orange and red with gradually increasing Sm3+ doping concentration. All results indicate the occurrence of the energy transfer which results in the color-tunable properties of the phosphors.

Investigations on photoluminescence properties of rare-earth ion single-doped CaSrSb2O7 phosphors

In this work, series of Sm3+ and Eu3+ single-doped CaSrSb2O7 phosphors were successfully synthesized via a high-temperature solid state method. The concentration quenching mechanism in both Sm3+ and Eu3+ activated phosphors was controlled by electric dipole-dipole interaction. The CaSrSb2O7: Sm3+ phosphors would emit color-tunable properties by adjusting doping concentration and temperatures. The optimal doping concentration of CaSrSb2O7: Sm3+ phosphors was determined to be 5 mol% while the corresponding Commission Internationale de I'Eclairage (CIE) chromatic coordinate would be (0.370, 0.423). In the meantime, the optimal doping concentration in CaSrSb2O7: Eu3+ phosphors was 20 mol%. CaSrSb2O7: 0.20Eu3+ phosphors have a CIE chromatic coordinate of (0.587,0.389) in orange red emission while the emission intensity at 423 K was still 50.69%, suggesting that the as-prepared CaSrSb2O7: Eu3+ phosphors with good thermal stability can be potential for solid-state lighting.

Structural and color tunable properties in Sm3+/Eu3+-doped Ca3Bi(PO4)3 phosphor for solar cell and w-LED applications

Structural and color tunable properties in Sm3+/Eu3+-doped Ca3Bi(PO4)3 phosphor for solar cell and w-LED applications

Effects of activated Sr 2+ ion content on strong blue‐emitting Ca 2 Sb 2 O 7 materials for high‐quality WLED devices

In this report, the luminescent performances of the self-host blue-emitting Ca2Sb2O7 materials were investigated in terms of the sintering temperature and the dopant Sr2+ ion content. The emission intensity was enhanced with an increase of the sintering temperature as well as the lattice parameters. After doping the Sr2+ ions (>1.2 mol%), the emission spectra of Ca2Sb2O7 materials would be redshifted. The blue-emitting color (Ca2Sb2O7) turned into greenish-blue (Sr2+@1.6 mol%) and green (Sr2+@2 mol%) colors in sequence. In light of these interesting findings, the crystal structure, elemental composition, morphology, thermal stability, luminescent dynamics, luminescent efficiency, etc were investigated and compared. Finally, the mini-white lighting-emitting diodes (WLEDs) based on the blue-emitting Ca2Sb2O7, greenish-blue-emitting Ca0.4Sr1.6Sb2O7, and green-emitting Sr2Sb2O7 phosphors were fabricated by mixing commercial phosphors (CP). Especially, the Ca2Sb2O7-CP-WLED and Sr2Sb2O7-CP-WLED devices exhibited a warm white light with good correlated color temperature (<3200 K) and excellent color-rendering index (>88). All the above results suggested that the self-host emitting materials of Sr2+ activated Ca2Sb2O7 with color-tunable properties could be very promising for solid-state lighting applications.