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Structures and isomerization scheme of the compounds used in this study. The shaded arrows indicate the FRET (Förster Resonance Energy Transfer) processes and the accompanying changes in the emission color. Please note that the photoinduced ring-opening reactions DAE(c) → DAE(o) induced by visible light (Vis) are too inefficient to influence the isomeric distributions with the herein applied irradiation wavelengths
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On-command changes in the emission color of functional materials is a sought-after property in many contexts. Of particular interest are systems using light as the external trigger to induce the color changes. Here we report on a tri-component cocktail consisting of a fluorescent donor molecule and two photochromic acceptor molecules encapsulated i...
Citations
... In other words, molecular structures based on photoluminescence structure and photoswitch are usually incompatible within the same chromophore. Other approaches, such as connecting separate luminophore and photoswitchable chromophore in a non-conjugated or even non-covalent form usually results in undesired residual peaks leading to heterochromatic emission 18,[23][24][25][26][27] . Additionally, compositing or doping molecular photoswitches into photonic crystal systems could drive luminescence shift more thoroughly, but such systems are hard to be carried out in nanoscale or in well-defined nanostructures [28][29][30][31][32] . ...
Photocontrollable luminescent molecular switches capable of changing emitting color have been regarded as the ideal integration between intelligent and luminescent materials. A remaining challenge is to combine good luminescence properties with wide range of wavelength transformation, especially when confined in a single molecular system that forms well-defined nanostructures. Here, we report a π-expanded photochromic molecular photoswitch, which allows for the comprehensive achievements including wide emission wavelength variation (240 nm wide, 400–640 nm), high photoisomerization extent (95%), and pure emission color (<100 nm of full width at half maximum). We take the advantageous mechanism of modulating self-assembly and intramolecular charge transfer in the synthesis and construction, and further realize the full color emission by simple photocontrol. Based on this, both photoactivated anti-counterfeiting function and self-erasing photowriting films are achieved of fluorescence. This work will provide insight into the design of intelligent optical materials.
... There are two primary methods of color mixing: additive and subtractive. Subtractive mixing is used in pigment-based systems like printing, while additive mixing, also known as spectral mixing, is commonly employed in fluorescence microscopy and combines fluorophores to create new emission colors [36][37][38]. In this context, Grassmann's color mixing law has been utilized, with detailed explanations provided in the SM. ...
In the ratiometric fluorescent (RF) strategy, the selection of fluorophores and their respective ratios helps to create visual quantitative detection of target analytes. This study presents a framework for optimizing ratiometric probes, employing both two-component and three-component RF designs. For this purpose, in a two-component ratiometric nanoprobe designed for detecting methyl parathion (MP), an organophosphate pesticide, yellow-emissive thioglycolic acid-capped CdTe quantum dots (Y-QDs) (analyte-responsive), and blue-emissive carbon dots (CDs) (internal reference) were utilized. Mathematical polynomial equations modeled the emission profiles of CDs and Y-QDs in the absence of MP, as well as the emission colors of Y-QDs in the presence of MP separately. In other two-/three-component examples, the detection of dopamine hydrochloride (DA) was investigated using an RF design based on blue-emissive carbon dots (B-CDs) (internal reference) and N-acetyl L-cysteine functionalized CdTe quantum dots with red/green emission colors (R-QDs/G-QDs) (analyte-responsive). The colors of binary/ternary mixtures in the absence and presence of MP/DA were predicted using fitted equations and additive color theory. Finally, the Euclidean distance method in the normalized CIE XYZ color space calculated the distance between predicted colors, with the maximum distance defining the real-optimal concentration of fluorophores. This strategy offers a more efficient and precise method for determining optimal probe concentrations compared to a trial-and-error approach. The model’s effectiveness was confirmed through experimental validation, affirming its efficacy.
Graphical abstract
... 32−35 The metasurface is transferred onto a quartz substrate using a "floating off" technique and fixed on quartz by dangling bonding at the interface between c-Si and quartz, and a 300-nm-thick PMMA polymer doped with 0.1 wt % highquantum-yield dye molecules [diarylethene red (DAEr)] is spin-coated onto the surface ( Figure S1). 36 The bright-field and fluorescence microscopy images of three array samples are shown at the bottom of Figure 1a. Uniform diameters of the nanodisks (D = 200 nm) and periodicity of the array (P = 405 nm) are confirmed with SEM (Figure 1b), and the normalized PL spectrum and compound structure of DAEr are also illustrated in Figure 1c. ...
Optical bound states in the continuum (BICs) offer strong interactions with quantum emitters and have been extensively studied for manipulating spontaneous emission, lasing, and polariton Bose-Einstein condensation. However, the out-coupling efficiency of quasi-BIC emission, crucial for practical light-emitting devices, has received less attention. Here, we report an adaptable approach for enhancing quasi-BIC emission from a resonant monocrystalline silicon (c-Si) metasurface through lattice and multipolar engineering. We identify dual-BICs originating from electric quadrupoles (EQ) and out-of-plane magnetic dipoles, with EQ quasi-BICs exhibiting concentrated near-fields near the c-Si nanodisks. The enhanced fractional radiative local density of states of EQ quasi-BICs overlaps spatially with the emitters, promoting efficient out-coupling. Furthermore, coupling the EQ quasi-BICs with Rayleigh anomalies enhances directional emission intensity, and we observe inherent opposite topological charges in the multipolarly controlled dual-BICs. These findings provide valuable insights for developing efficient nanophotonic devices based on quasi-BICs.
... (S)-CNB emits blue fluorescence at 436 nm in the 5CB host and shows a high fluorescence quantum yield of 32.46%, accompanied by a strong right-handed CPL with a g lum value of up to −0.33 ( Fig. 2a After isomerization to their closed-forms, the absorption peaks dramatically redshift to the visible region and largely overlap with the peaks in the emission spectra of (S)-CNB and closed-DG, respectively (Fig. 2d). It is well known that FRET efficiency strongly depends on the spectral overlapping area and the distance between the donor and acceptor (i.e., the concentration of acceptor) [52][53][54] . The ideal spectral features of DG and DR enable phototunable FRET processes. ...
Materials with phototunable full-color circularly polarized luminescence (CPL) have a large storage density, high-security level, and enormous prospects in the field of information encryption and decryption. In this work, device-friendly solid films with color tunability are prepared by constructing Förster resonance energy transfer (FRET) platforms with chiral donors and achiral molecular switches in liquid crystal photonic capsules (LCPCs). These LCPCs exhibit photoswitchable CPL from initial blue emission to RGB trichromatic signals under UV irradiation due to the synergistic effect of energy and chirality transfer and show strong time dependence because of the different FRET efficiencies at each time node. Based on these phototunable CPL and time response characteristics, the concept of multilevel data encryption by using LCPC films is demonstrated.
... Photochromic materials are of great interest because of their employment in light-responsive devices, as for example rewritable displays, dynamic optical filters and optical memories [1][2][3][4]. In photochromism, an electromagnetic radiation-induced reversible transformation, from a thermodynamically more stable isomer A into a metastable isomer B, occurs [5]. ...
Light responsive devices employing molecular photo-switches are interesting for displays and dynamic light filtering. In this work polymeric microcavities embedding a layer of photochromic compound have been studied by means of the transfer matrix method. Different polymers, such as poly vinyl carbazole, poly styrene and cellulose acetate, have been used. A microcavity that includes random one-dimensional photonic structures sandwiching the photochromic layer has also been studied. Propagation of light pulses through the microcavities has been analysed.
... In a wider context, beyond graphene, external control of FRET by light [37], mechanical stimuli [38,39], temperature and solvent [40], ions and pH [41], microfluidic flow [42], as well as electrical fields [43], has been achieved with the aim of constructing full color RGB displays [37], mechanical sensors [38], mechanical [39] and optoelectronic [14] switches, logic gates [41] or enhanced DNA sensors [42]. However, continuous modulation of the FRET efficiency between a donor and an acceptor by electric fields at room temperature has not been reported yet. ...
... In a wider context, beyond graphene, external control of FRET by light [37], mechanical stimuli [38,39], temperature and solvent [40], ions and pH [41], microfluidic flow [42], as well as electrical fields [43], has been achieved with the aim of constructing full color RGB displays [37], mechanical sensors [38], mechanical [39] and optoelectronic [14] switches, logic gates [41] or enhanced DNA sensors [42]. However, continuous modulation of the FRET efficiency between a donor and an acceptor by electric fields at room temperature has not been reported yet. ...
In artificial structures of molecular or quantum dot emitters in contact with single-layer graphene (SLG) Förster-type resonant energy transfer (FRET) can occur unconditionally due to the gapless band structure of SLG. A significant breakthrough for applications, however, would be the electrical modulation of FRET between arbitrary FRET pairs, using the SLG to control this process and taking advantage of the particular band structure and the monatomic thickness of SLG, far below the typical Förster radius of a few nanometers. For a proof of concept, we have therefore designed a Sandwich device where the SLG was transferred onto holey Si3N4 membranes and organic molecules were deposited on either side of the SLG. The relative photoluminescence (PL) intensities of donor and acceptor molecules changed continuously and reversibly with the external bias voltage, and a variation of about 6% of FRET efficiency has been achieved. We ascribe the origin of the electrical modulation of FRET to important doping-dependent nonlocal optical effects in the near field of SLG in the visible range.
... 44 The secondary colors are obtained when two of the primary colors at the same intensity are combined. The software ImageJ (i.e., a free software employed for the analysis of the images) 45,46 allows us to measure the intensity of individual pixels or a selected area of the image, providing quantitative data based on the RGB system by giving three numbers that correspond to the intensity of the red, green, and blue colors, respectively. 45 Furthermore, we optimized the concentrations of the previously characterized blue, green, and red QDs so that they can display the same fluorescence intensity ( Figure S7). ...
... The software ImageJ (i.e., a free software employed for the analysis of the images) 45,46 allows us to measure the intensity of individual pixels or a selected area of the image, providing quantitative data based on the RGB system by giving three numbers that correspond to the intensity of the red, green, and blue colors, respectively. 45 Furthermore, we optimized the concentrations of the previously characterized blue, green, and red QDs so that they can display the same fluorescence intensity ( Figure S7). Then, we mixed red QDs at 25 nM with green QDs at 200 nM to obtain a fluorescence signal corresponding to the yellow color, red QDs at 25 nM with blue QDs at 50 nM to obtain magenta, and green QDs at 200 nM with blue QDs at 50 nM to obtain cyan ( Figure 2C). ...
The quantitative detection of different molecular targets is of utmost importance for a variety of human activities, ranging from healthcare to environmental studies. Bioanalytical methods have been developed to solve this and to achieve the quantification of multiple targets from small volume samples. Generally, they can be divided into two different classes: point of care (PoC) and laboratory-based approaches. The former is rapid, low-cost, and user-friendly; however, the majority of the tests are semiquantitative, lacking in specificity and sensitivity. On the contrary, laboratory-based approaches provide high sensitivity and specificity, but the bulkiness of experimental instruments and complicated protocols hamper their use in resource-limited settings. In response, here we propose a smartphone-based device able to support laboratory-based optical techniques directly at the point of care. Specifically, we designed and fabricated a portable microplate reader that supports colorimetric, fluorescence, luminescence, and turbidity analyses. To demonstrate the potential of the device, we characterized its analytical performance by detecting a variety of relevant molecular targets (ranging from antibodies, toxins, drugs, and classic fluorophore dyes) and we showed how the estimated results are comparable to those obtained from a commercial microplate reader. Thanks to its low cost (<$300), portability (27 cm [length] × 18 cm [width] × 7 cm [height]), commercially available components, and open-source-based system, we believe it represents a valid approach to bring high-precision laboratory-based analysis at the point of care.
... Organic micro/nanocrystals have been demonstrated as brilliant building-blocks for the miniaturized devices [1][2][3], electrochemical sensors [4][5][6][7], organic light-emitting diodes (OLEDs) [8,9], solar cells [10,11], and organic field-effect transistors [12,13], and thus have drawn enormous attention from researchers [14]. Compared with the inorganic materials, which occupy strong market positions and accessibility to the manufacturing infrastructure, the organic counterparts play a unique role due to the broad spectral tunability, high optical crosssections as well as low-cost solution processing [15][16][17]. What's more, the periodic molecular packing mode in the micro/ nanocrystals leads to a higher mobility and regular morphology, which make them distinguish from the amorphous structures and polymers [18][19][20]. ...
Organic micro/nanocrystals based on small organic molecules have drawn extensive attention due to their potential application in organic field-effect transistors, electrochemical sensors, solar cells, etc. Herein, the recent advances for organic micro/nanocrystals from the perspective of molecule aggregation mode, morphology modulation, and optical property modulation are reviewed. The stacking mode and the intermolecular interaction depend on the molecular structure, which eventually determines the morphology of organic micro/nanocrystals. The morphologies of the organic micro/nanocrystals make the aggregates exhibit photon confinement or light-guiding properties as organic miniaturized optoelectronic devices. In this review, we conclude with a summary and put forward our perspective on the current challenges and the future development of morphology and optical tunable direction for the organic micro/nanocrystals.
... The number of fluorescent states within one system can be expanded by incorporating different kinds of fluorescent photochromics. Recently, several kinds of PMFMs including well-defined single molecules, nanoparticles, and doped polymer systems, have been reported [45][46][47][48][49][50]. These PMFMs can display distinct multistate switching among no-red-green fluorescence or red-greenblue fluorescence but have some drawbacks for practical application, such as requiring tedious synthesis processes (single molecules), showing low structural stability due to non-covalent doping or mixing structures (doped polymers), or being difficult to form self-standing film and processed (nanoparticles), and therefore, could not meet the criteria required for practical applications like optical data storage and information encryption. ...
Stimuli-responsive fluorescent materials that can alternate their emission states on-demand are always desired in many applications. In this study, novel photoswitchable multistate fluorescent polymer (PMFP) was prepared via simple free-radical copolymerization of butyl acrylate (BA) and styrene (St) with two photochromic fluorescent monomers, i.e. sulfonyl diarylethylene-linked 4-hydroxybutyl acrylate (SDTE) and spiropyran-linked methacrylate (SP8). The PMFP displays excellent processability, due to its rational feed ratio of BA and St which result in the relative low glass transition temperature. By changing irradiation light, the non-fluorescent ring-closed spiropyran units and ring-opened diarylethylene moieties in PMFP can be selectively converted into their corresponding luminescence states. Furthermore, as a result of the controllable fluorescence resonance energy transfer (FRET) from the excited diarylethylene to the spiropyran moieties, the emission of the polymer in solution or film can be reversibly switched among distinguishable no-emission, red, and green fluorescence states. Moreover, the PMFP exhibits high brightness, high contrast, rapid photoresponse, and excellent photoreversibility. We also demonstrated that PMFP can be directly used for advanced high-density data storage, multilevel information encryption, and multicolor photorewritable pattern, as well as high-level anticounterfeiting.
... Similar to changing the doping ratio of the lanthanide of UCNPs or adjustment of the halide ion of perovskite NPs, changing the solvent of the dye can also adjust its fluorescence lifetime to realize lifetime-based encryption. Additive mixing, that is, changes in the overall emission color of a sample achieved by mixing two or more individual fluorophores in different ratios has been successfully applied [20]. Huang et al. [21] tuned the emission color of a single-component molecular crystal by varying the excitation wavelength, allowing to visually detection of specific wavelengths in the UV region. ...
The turn-off fluorescent photoswitches for information encryption are constantly being developed. However, there are no reports about time-switchable (fluorescence lifetime-switchable) encryption to overcome the limitations of tunable encoding numbers in spectrally and temporally encoded libraries. Based on the double-exponential fitting of fluorescence lifetime, we propose, a fatigue-free and highly flexible switch between the amplitude-weighted average fluorescence lifetime ( τm ) and the intensity-weighted average fluorescence lifetime ( τi ), which will realize the supermultiplexed fluorescence lifetime switchable encryption. The potentially enormous library of different fluorescent lifetime combinations would facilitate the development of information security.
