Color Tuning Research Articles

Tuning Molecular Packing by Twisting Structure to Facilely Construct Highly Efficient Solid‐State Fluorophores for Two‐Photon Bioimaging and Photodynamic Therapy

AbstractThe traditional design strategy for constructing highly bright solid‐state luminescent materials relies on incorporating aggregation‐induced emission (AIE) scaffolds, molecular rotors, or bulky substituents to prevent close cofacial packing, which limits the strategy diversity in developing new materials. Herein, a strategy of tuning molecular packing by twisting molecular structure of conventional aggregation‐caused quenching fluorophore is proposed to endow materials with AIE effect and enhance the solid‐state fluorescence. Accordingly, a series of 1,4‐bis(diphenylamino)‐2,5‐disubstituted benzene fluorophores exhibiting AIE characteristics, high solid‐state fluorescence efficiency (up to 0.99), wide emission color tunability, and good near‐infrared (NIR) two‐photon absorption is facilely developed. All these luminogens can specifically stain intracellular lipid droplets with a high signal‐to‐noise ratio, high biocompatibility, and good photostability. Besides, the luminogens exhibit effective reactive oxygen species (ROS) generation capability upon low‐power white light irradiation. Among them, the AIE luminogen, named BDBDC, integrating the NIR emission, good NIR two‐photon absorption and strongest ROS generation demonstrates superior performances in two‐photon fluorescence imaging of various tissues and photodynamic cancer therapy. This molecular design philosophy provides a new way of designing highly bright solid‐state fluorophores for practical applications.

Color construction of multi-colored carbon fibers using glucose

Carbon fibers (CFs) have attracted attention in the automotive, aviation, and aerospace industries. However, the coloration of CFs is challenging due to their brittleness, inertness, complexity, and time/energy-intensive processes. Herein, inspired by the naturally grown protrusive nanostructures on the green central surface of peacock back feathers, we report an in-situ self-growing strategy for developing carbon spheres (CSs) on the CFs surface to achieve color tuning. This is achieved via the dynamic growth of CSs using glucose as the feeding material. Combined with the coloration process, the interaction between CSs and CFs promotes stable interfacial forces in integrated molding. This strategy allows the coloring system to continuously vary its color in a designated manner, thereby, endowing it with satisfactory mechanical robustness, acid durability, and light fastness. We anticipate this developed approach can be potentially competitive in the color construction of CFs with multi-colors due to its low-cost manufacturing.

Spatiotemporal control of photochromic upconversion through interfacial energy transfer

Dynamic control of multi-photon upconversion with rich and tunable emission colors is stimulating extensive interest in both fundamental research and frontier applications of lanthanide based materials. However, manipulating photochromic upconversion towards color-switchable emissions of a single lanthanide emitter is still challenging. Here, we report a conceptual model to realize the spatiotemporal control of upconversion dynamics and photochromic evolution of Er3+ through interfacial energy transfer (IET) in a core-shell nanostructure. The design of Yb sublattice sensitization interlayer, instead of regular Yb3+ doping, is able to raise the absorption capability of excitation energy and enhance the upconversion. We find that a nanoscale spatial manipulation of interfacial interactions between Er and Yb sublattices can further contribute to upconversion. Moreover, the red/green color-switchable upconversion of Er3+ is achieved through using the temporal modulation ways of non-steady-state excitation and time-gating technique. Our results allow for versatile designs and dynamic management of emission colors from luminescent materials and provide more chances for their frontier photonic applications such as optical anti-counterfeiting and speed monitoring.

Aesthetic Cellulose Filaments with Water-Triggered Switchable Internal Stress and Customizable Polarized Iridescence Toward Green Fashion Innovation.

Healthy, convenient, and aesthetic hair dyeing and styling are essential to fashion trends and personal-social interactions. Herein, we fabricate green, scalable, and aesthetic regenerated cellulose filaments (ACFs) with customizable iridescent colors, outstanding mechanical properties, and water-triggered moldability for convenient and fashionable artificial hairdressing. The fabrication of ACFs involves cellulose dissolution, cross-linking, wet-spinning, and nanostructured orientation. Notably, the cross-linking strategy endows the ACFs with significantly weakened internal stress, confirmed by monitoring the offset of the C-O-C group in the cellulose molecular chain with Raman imaging, which ensures a tailorable orientation of the nanostructure during wet stretching and tunable iridescent polarization colors. Interestingly, ACFs can be tailored for three-dimensional shaping through a facile water-triggered adjustable internal stress: temporary shaping with low-level internal stress in the wet state and permanent shaping with high-level internal stress in the dry state. The health, convenience, and green aesthetic filaments show great potential in personal wearables.

Multisite Fine-Tuning in Hybrid Cadmium Halides Enables Wide Range Emissions for Anti-Counterfeiting.

Achieving tunable emissions spanning the spectrum, from blue to near-infrared (NIR) light, within a single component is a formidable challenge with significant implication, particularly in tailoring multicolor luminescence for anti-counterfeiting purposes. In this study, we demonstrate a broad spectrum of emissions, covering blue to red and extending into NIR light in [BPy]2CdX4 : xSb3+ (BPy=Butylpyridinium; X=Cl, Br; x=0 to 0.08) through precise multisite structural fine-tuning. Notably, the multicolor emissions from [BPy]2CdBr4 : Sb3+ manifest a distinctive pattern, transitioning from blue to yellow in tandem with the host [BPy]2CdBr4 and further extending from yellow to NIR with its homologous [BPy]2CdCl4 : Sb3+, resulting in the simultaneous presence of intersecting and independent emission colors. Detailed modulation of chemical composition enables partial luminescence switching, facilitating the creation of diverse patterns with multicolor luminescence by employing [BPy]2CdX4 : xSb3+ as phosphors. This study for the first time successfully implements several groups of tunable emission colors in a single matrix via multisite fine-tuning. Such an effective strategy not only develops the specific relationships between tunable emissions and adjustable compositions, but also introduces a cost-effective and straightforward approach to achieving unique, high-level, plentiful-color and multiple-information-storage labels for advanced anti-counterfeiting applications.

Multisite Fine‐Tuning in Hybrid Cadmium Halides Enables Wide Range Emissions for Anti‐Counterfeiting

AbstractAchieving tunable emissions spanning the spectrum, from blue to near‐infrared (NIR) light, within a single component is a formidable challenge with significant implication, particularly in tailoring multicolor luminescence for anti‐counterfeiting purposes. In this study, we demonstrate a broad spectrum of emissions, covering blue to red and extending into NIR light in [BPy]2CdX4 : xSb3+ (BPy=Butylpyridinium; X=Cl, Br; x=0 to 0.08) through precise multisite structural fine‐tuning. Notably, the multicolor emissions from [BPy]2CdBr4 : Sb3+ manifest a distinctive pattern, transitioning from blue to yellow in tandem with the host [BPy]2CdBr4 and further extending from yellow to NIR with its homologous [BPy]2CdCl4 : Sb3+, resulting in the simultaneous presence of intersecting and independent emission colors. Detailed modulation of chemical composition enables partial luminescence switching, facilitating the creation of diverse patterns with multicolor luminescence by employing [BPy]2CdX4 : xSb3+ as phosphors. This study for the first time successfully implements several groups of tunable emission colors in a single matrix via multisite fine‐tuning. Such an effective strategy not only develops the specific relationships between tunable emissions and adjustable compositions, but also introduces a cost‐effective and straightforward approach to achieving unique, high‐level, plentiful‐color and multiple‐information‐storage labels for advanced anti‐counterfeiting applications.

Colorful multi-plane augmented reality display with dynamically tunable reflective Pancharatnam-Berry phase lens.

Reflective cholesteric liquid crystal (CLC) Pancharatnam-Berry phase lens (PBL) devices have attracted significant attention in augmented reality (AR) display due to their wide spectral and angular response bandwidths, high diffraction efficiency, and polarization selectivity. However, currently reported CLC reflective PBLs are either limited by monochrome display or suffers from complicated design for colorful display. Herein, we demonstrate a colorful multi-plane AR display system with dynamically tunable reflective PBL. The reflective PBL is fabricated by polymer-stabilized cholesteric liquid crystal (PSCLC) that provides dynamical and continuous tunability of color and focal length by direct current (DC) voltage. A proof-of-concept colorful multi-plane AR device is demonstrated, where over 90% diffraction efficiency at desired wavelength has been obtained. The proposed simple, compact, and light AR display system capable of color-imaging with multi-depth shows great application potential in the vehicle-mounted head-up display (HUD).

Scalable, Green, Flexible Photochromic Bacterial Cellulose for Multicolor Switching, Photo-patterning, and Daily Sunlight UV Monitoring.

Sustainable, durable, and diverse photochromic smart textiles based on bacterial cellulose (BC) have emerged as attractive candidates in UV-sensing applications due to the green and easy functionalization of BC. However, existing BC-based photochromic textiles lack photochromic efficiency and combining fastness. In this study, a green strategy for in situ fermentation is developed to achieve the directional distribution of functional particles and remarkable photochromism in photochromic bacterial cellulose (PBC). The unique functional design obtained by regulating the photochromic dye distribution in 3D nanonetworks of PBCs during in situ growth affords a more uniform distribution and high fastness. Benefiting from the uniform distribution of photochromic dyes and adequate utilization of the 3D network structure, more surface area is provided to receive and utilize the photon energy from the UV rays, making the photochromic process more effective. The as-prepared PBCs exhibited rapid (within 1min) and stable (30 cycles) discoloration and multicolor selectivity. Their simple preparation process and exceptional wearability, e.g., their flexibility, lightweight, and air permeability, make them suitable for various applications, including tunable color switching systems, photopatterning, and daily sunlight UV monitoring. This study provides empirical value for the biofabrication of photochromic textiles and wearable flexible UV sensors.

Direct in Situ Fabrication of Multicolor Afterglow Carbon Dot Patterns with Transparent and Traceless Features via Laser Direct Writing.

Multicolor afterglow patterns with transparent and traceless features are important for the exploration of new functionalities and applications. Herein, we report a direct in situ patterning technique for fabricating afterglow carbon dots (CDs) based on laser direct writing (LDW) for the first time. We explore a facile step-scanning method that reduces the heat-affected zone and avoids uneven heating, thus producing a fine-resolution afterglow CD pattern with a minimum line width of 80 μm. Unlike previous LDW-induced luminescence patterns, the patterned CD films are traceless and transparent, which is mainly attributed to a uniform heat distribution and gentle temperature rise process. Interestingly, by regulating the laser parameters and CD precursors, an increased carbonization and oxidation degree of CDs could be obtained, thus enabling time-dependent, tunable afterglow colors from blue to red. In addition, we demonstrate their potential applications in the in situ fabrication of flexible and stretchable optoelectronics.

Tailoring raloxifene into single-component molecular crystals possessing multilevel stimuli-responsive room-temperature phosphorescence

Simultaneously achieving room-temperature phosphorescence (RTP) and multiple-stimuli responsiveness in a single-component system is of significance but remains challenging. Crystallization has been recognized to be a workable strategy to fulfill the above task. However, how the molecular packing mode affects the intersystem crossing and RTP lifetime concurrently remains unclear so far. Herein, four economic small-molecular compounds, analogues of the famous drug raloxifene (RALO), are facilely synthesized and further explored as neat single-component and stimuli-responsive RTP emitters via crystallization engineering. Thanks to their simple structures and high ease to crystallize, these raloxifene analogues function as models to clarify the important role of molecular packing in the RTP and stimuli-responsiveness properties. Thorough combination of the single-crystal structure analysis and theoretical calculations clearly manifests that the tight antiparallel molecular packing mode is the key point to their RTP behaviors. Interestingly, harnessing the controllable and reversible phase transitions of the two polymorphs of RALO-OAc driven by mechanical force, solvent vapor, and heat, a single-component multilevel stimuli-responsive platform with tunable emission color is established and further exploited for optical information encryption. This work would shed light on the rational design of multi-stimuli responsive RTP systems based on single-component organics.

Thermally Induced Lattice-Defective Oxygen Breathing in Perovskite-Structure Stannates with High-Contrast Reversible Thermochromism.

Inorganic thermochromic materials exhibit a tunable color gamut and a wide chromatic temperature range, indicating their potential for intelligent adaptive applications in thermal warning, temperature indication, thermal regulation, and interactive light-to-thermal energy conversion. However, most metal-oxide-based thermochromic materials show weak chromaticity adaption with the change of temperature, which needs further understanding of the microscopic principle to clarify the potential route to improve the contrast and identifiability for fabricating better thermochromic materials. Using perovskite-structure (AMO3) alkaline earth metal stannate (Ba1-xSrxSnO3, 0.0 ≤ x ≤ 1.0) as a model system, this paper reports for the first time the mechanism of the properties of thermally induced defect-enhanced charge transfer-type (CTT) thermochromic materials and the strategy for regulating their thermochromic properties by A-site cations. BaSnO3 exhibits continuously reversible thermochromic properties with high contrast from weak light yellow (b* = 11) to strong bright yellow (b* = 58) between room temperature and 550 °C. In-situ high-temperature X-ray diffraction (in-situ XRD), in-situ UV-vis absorption spectroscopy (in-situ UV-vis), thermogravimetric (TG), and electron paramagnetic resonance (EPR) spectra indicate that this excellent thermochromic phenomenon is attributed to the weakening of Sn-O bond hybridization at high temperatures, as well as the formation of a large number of oxygen vacancies at the top of the valence band, and the enhanced charge transfer resulting from the generation of impurity levels in the Sn2+ 5s2 intermediate. Replacing Ba2+ by Sr2+ in Ba1-xSrxSnO3 successfully tuned the thermochromic properties, which is attributed to the Sr2+ doping level-directed oxygen defect concentration and deoxygenation rate. The demonstrated defect-enhanced charge transfer behavior promotes a feasible route for lattice oxygen-mediated thermochromic materials and provides a fundamental relationship between thermally induced defects and colorimetry.

Direct Visualization of Confinement and Many‐Body Correlation Effects in 2D Spectroscopy of Quantum Dots

AbstractThe size tunable color of colloidal semiconductor quantum dots (QDs) is probably the most elegant illustration of the quantum confinement effect. As explained by the simple “particle‐in‐a‐box” model, the transition energies between the levels increase when the “box” becomes smaller. To investigate quantum confinement effects, typically a well‐defined narrow size distribution of the nanoparticles is needed. In this contribution, how coherent electronic two‐dimensional spectroscopy (2DES) can directly visualize the quantum size effect in a sample with broad size distribution of QDs is demonstrated. The method is based on two features of the 2DES – the ability to resolve inhomogeneous broadening and the capability to reveal correlations between the states. In QD samples, inhomogeneous spectral broadening is mainly caused by the size distribution and leads to elongated diagonal peaks of the spectra. Since the cross peaks correlate the energies of two states, they allow drawing conclusions about the size dependence of the corresponding states. It is also found that the biexciton binding energy changes between 3 and 8 meV with the QD size. Remarkably, the size dependence is non‐monotonic with a clear minimum.

Ultralong sodium alginate-based room temperature phosphorescence materials with advantages of color tunability, flexibility and facile large-area fabrication

Organic room temperature phosphorescence (RTP) has promising applications in diverse fields, whereas a formidable challenge remains in the development of flexible organic RTP materials, especially environmentally friendly RTP materials. In this work, natural polymer sodium alginate (SA)-based RTP materials have been facilely developed by doping phenylboronic acid (PBA) and its derivatives into SA matrices. 4-carboxyphenylboric acid doped system SA-CPBA exhibits the best RTP performance with an ultralong phosphorescence lifetime of up to 231 ms. Interestingly, SA-CPBA shows excitation-dependent phosphorescence color tunability by water vapor fumigation and heating, and the afterglow color change has good reversibility upon alternating treatment of water vapor fumigation and heating. Amazingly, flexible and transparent RTP films are obtained through adding a certain amount of glycerol (G) into SA-CPBA matrices, and SA-CPBA-G also possesses excellent excitation-dependent phosphorescence color tunability. Furthermore, the flexible SA-CPBA-G film can be conveniently fabricated on a large area. These excellent features enable the prepared SA-based RTP materials to be successfully applied in the fields of flexible display and information encryption. This work provides a guideline for the preparation of environmentally friendly flexible polymer-based color-tunable RTP materials and expands the application range of SA-based materials to the field of flexible displays.

Ba3Lu(BO3)3:Ce3+,Tb3+/Mn2+: Dual-Functional Material for WLEDs and Optical Pressure Sensing.

Ba3Lu(BO3)3(BLB):Ce3+,Tb3+/Mn2+ phosphors were designed to explore effective and multifunctional applications. Under the excitation of near-ultraviolet (n-UV) light, the BLB:Ce3+ phosphor showed broad-band blue emission. After codoping with Mn2+ ions, the single-phase white light phosphor is achieved through the energy transfer (ET) between Ce3+ and Mn2+. In addition, thermal stability is significantly enhanced by the addition of Tb3+ (BLB:0.02Ce3+,0.20Tb3+) compared to that codoped with Mn2+ (BLB:0.02Ce3+,0.10Mn2+). The light-emitting diode (LED) device with warm white light emission is fabricated with UV-chip-coated BLB:0.02Ce3+,0.05Tb3+ and Sr2Si5N8:Eu2+ phosphors, showing a good potential application value for LEDs. Additionally, the spectral properties of borate-based phosphors (BLB:0.02Ce3+) under high pressure were studied for the first time. Surprisingly, the change of pressure enabled the emission peak of BLB:0.02Ce3+ to be tuned from 485 to 552 nm, and dλ/dP is 3.51 nm GPa-1. The color changes from blue to yellow with an increase of pressure. Compared with the reported data, the pressure-sensing sensitivity based on the central peak shift in this work is the highest in all Ce3+ single-doped samples. In addition, the emitting color and intensity were gradually regained after decompression. The intensity can reach 80% of the initial intensity. All data demonstrate that the BLB:0.02Ce3+ phosphor has the potential to be utilized as an optical pressure sensor due to the high-pressure sensitivity and visible color tuning.

Film thickness dependent color purity of WOLEDs in a Phenanthroimidazole derivative due to electromers

Recently, derivatives of Phenanthroimidazole (Phen-I) based small molecules have been synthesized for OLED applications. Their photophysical characterization revealed they were fluorescent with a high quantum yield, indicating their suitability as an emissive layer (EML) in OLEDs. In this paper, we report and compare the OLED performance of two Phen-I derivatives. One contains thiophene (compound 1), and the other, newly designed and synthesized, has perylene (compound 2) as a functional group. Devices of 1 with lower EML thickness (∼70 nm) showed bluish white emission, while devices with higher EML thickness (> ∼100 nm) showed color tunability from bluish-white (CIE co-ordinates: (0.26, 31)) light at lower voltage to almost pure white (CIE co-ordinates: (0.29, 32)) light at higher voltages forming WOLED. The WOLED formed for 1 at all thickness of the EML is attributed to the combined monomer and electromer emission. In addition, the voltage-dependent change in colour purity observed for higher EML thickness is attributed to increased electromer species, indicating stronger intermolecular interactions due to well-connected grains in their thin films. In contrast, devices of compound 2 showed yellow-orange emission independent of the thickness of the EML. The optimized geometry for all devices was ITO/PEDOT: PSS /NPD/1 or 2 /BPhen/LiF-Al. Devices of 2 were more efficient than those of 1, indicating that forming electromers, though advantageous in giving WOLEDs, reduces the device efficiency.

Position and Number Do Matter: Tuning Room Temperature Phosphorescence in Bromo‐1,8‐Naphthalimides through H‐Aggregation and Halogen Bonding

AbstractDevelopment of purely organic room temperature phosphors can often be obtained via introduction of heavy atoms into the organic scaffold. However, the task of controlling emission properties in room temperature phosphorescent (RTP) crystals via heavy atom substitution has met limited success. Herein, two classes of molecules (NIpBr1‐2 and NImBr1‐2) are designed by varying position (para and meta) as well as number of bromo substituents in 1,8‐naphthalimide to modulate intermolecular interactions and their phosphorescence properties. NIpBr2 features only halogen bonding. NIpBr, NImBr, and NImBr2 feature H‐aggregation in their crystalline packing wherein the efficiency of H‐aggregation increases as NIpBr < NImBr < NImBr2. NImBr2 also features halogen bonding in addition to H‐aggregation. Relative phosphorescence intensity, phosphorescence lifetime and quantum yield increase in the order NIpBr2 < NIpBr < NImBr < NImBr2, endorsing cruciality of bromine atom positioning and numbering in tuning the RTP performance. Amplification of phosphorescence in meta derivatives over the para congeners leads to tunable emission color of the crystals from blue to orange. These results outline a predictive structure‐property relationship wherein judicious choice of both position and number of bromine substitution can help in regulating emission behavior, providing a major step forward in expanding the fundamentals of organic RTP.

Comprehensive performance of polycarbonate films doped with Tb(III) and Eu(III) complexes

AbstractIn order to expand the application of biobased polycarbonate in optical components, a series of isosorbide polycarbonate (PICC)/rare earth ion complex fluorescent composites were prepared by using PICC as a macromolecular ligand and Eu3+ and Tb3+ as rare earth luminescence centers. The coordination system between rare earth ions and PICC was investigated by Fourier transform infrared spectroscopy, DSC and TGA. On adjusting the ratio of Eu3+ and Tb3+, a PICC/rare earth ion composite with adjustable fluorescence color was obtained. Also, the thermal, mechanical and optical properties of a series of PICC/rare earth ion fluorescent films with different ratios were tested. A transparent fluorescent composite material with excellent mechanical properties and tunable fluorescent colors has been prepared. © 2024 Society of Industrial Chemistry.

Chameleon-inspired supramolecular materials based on cucurbit[7]uril and viologens exhibiting full-color tunable photochromic behavior

Inspired by Chameleons' skin color tuning in response to environmental changes, we design and prepare three inclusion complexes based on the cucurbit[7]uril (Q[7]) host and three viologen guests. Upon light irradiation, the colors of these inclusion complexes in the solid state turn from light colors to vivid three primary colors, i.e., red, green, and blue, respectively. Ultraviolet–visible (UV–vis) diffuse reflectance and electron spin resonance (ESR) spectra reveal that the photochromism can be attributed to the generation of viologen radicals, originating from the photoinduced electron transfer. The results of quantum chemical calculation indicate that Q[7] in the inclusion complexes acts as the electron donor in the photoinduced electron transfer process. Using a color mixing approach and finely manipulating the proportions of the three inclusion complexes, a series of composite photochromic materials (CPMs) can be manufactured, covering a full-color gamut in visible light. On the other hand, due to the ignorable size and shape change of CPMs during the photochromatic processes, the CPMs-based reversible photochromic “printing” and photofading “erase” properties were also used for quick response (QR) code. Therefore, these prominent intelligent features of CPMs open new avenues to explore optical regulated nano-platforms for multiple anti-counterfeiting, biomimetics, and military camouflage applications.

Stretchable structural colors with polarization dependence using lithium niobate metasurfaces.

Independently tunable biaxial color pixels, composed of isolated nanosquare dimers, are demonstrated in this study. These pixels are capable of displaying a full range of colors under a linear-polarization dependent reflection mode. The metasurface is constructed by arranging LiNbO3 nanodimers on a PDMS substrate. By exciting a strong magnetic dipole (MD) resonance and effectively suppressing other multipolar resonances using surface lattice resonances, the researchers achieved a single reflection peak with a bandwidth of less than 9 nm and a reflective efficiency of up to 99%. Additionally, the stretchability of the PDMS substrate allows for active and continuous tuning of the metasurface by up to 40% strain, covering almost 150 nm of the visible light spectrum and enabling changes in reflection color. This metasurface holds potential applications in various fields, such as color displays, data storage, and anti-counterfeiting technologies.

Enhanced Efficiency, Broadened Excitation, and Tailored Er3+ Luminescence Triggered by Te4+ Codoping in Cs2NaYbCl6 Crystals for Multifunctional Applications.

The quest for efficient and tunable luminescent materials has been at the forefront of research in the fields of chemistry and materials science. This work delves into the investigation of the luminescence properties of Er3+ ions triggered by 1% Te4+ in the environmentally benign perovskite Cs2NaYbCl6 (CNYC) crystals, aiming to enhance their efficiency and tune the luminescence color. The ratio of the green (2H11/2, 4S3/2-4I15/2) to red (4F9/2-4I15/2) emissions of Er3+ can be freely tunable by varying the concentration of Er3+ and producing the defects induced by codoping Te4+. The calculations reveal that the multiexcitonic excitations of Er3+ stem from f-f (4I15/2-4G11/2, 2H9/2) rather than d-f transitions. The broadened excitation, tuning of color, and enhancement of efficiency achieved in the luminescence perovskite crystals Cs2NaYbCl6:Te4+, Er3+ (CNYC:Te4+,Er3+) presents promising opportunities for the development of advanced optoelectronic devices with superior performance. Moreover, our investigation demonstrates the tunable luminescence response of CNYC:Er3+ to temperature variations, offering potential applications in temperature sensing.