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Mechanochromic functionality realized via the force‐responsive mechanophores in polymers has great potential for damage sensing and information storage. Mechanophores with the ability to recognize multiple stimuli for tunable chromic characteristics are highly sought after for versatile sensing ability and color programmability. Nevertheless, the majority of mechanophores are based on single‐component chromophores with limited sensitivity, or require additional fabrication technology for multi‐modal chromism. Here, we report a novel multifunctional mechanophore capable of vividly detectable and tunable mechanochromism in polymers. This synergistic optical coupling relies on strategically fusing rhodamine and spiropyran (Rh−SP), and tethering polymer chains on both subunits. The mechanochromic behaviors of the Rh−SP‐linked polymers under sonication and compression are thoroughly evaluated in response to changes in force and the light‐controlled relaxation process. Non‐sequential ring‐opening of the two subunits under force is identified, endowing high‐contrast mechanochromism. Light‐induced differential ring‐closing reactions of the two subunits, together with the acidichromism of the SP moiety, are employed to engineer elastomers with programmable and wide‐spectrum colors. Our work presents an effective strategy for highly appreciable and regulable mechanochromic functionality, and also provides new insights into the rupture mechanisms of π‐fused mechanophores, as well as how the stimuli history controls stress accumulation in polymers. [ABSTRACT FROM AUTHOR]

A rhodamine-triazole fluorescent probe bearing a coumarin moiety RTC was synthesized using the Cu(I)-catalyzed click reaction. The rhodamine-triazole conjugate was highly selective to Cu2+ among other metal ions, including Ca2+, Co2+, Cu2+, Cd2+, Mg2+, Fe2+, Fe3+, Hg2+, Zn2+, Ni2+, Pd2+ and Pb2+ in physiological conditions. Upon the addition of Cu2+, the colorless RTC solution turned pink and exhibited a significant fluorescence emission centered at 578 nm. The binding of Cu2+ induced a hydrolysis reaction, leading to a release of the coumarin unit from the rhodamine probe, as confirmed by mass spectrometric data. From the fluorescence titration, the detection limit of RTC for Cu2+ was determined to be 21 nM (1.3 ppb). The sensor was responsive to Cu2+ in a wide pH range and successfully applied to monitor Cu2+ in HEK293T cells by confocal fluorescence imaging. [ABSTRACT FROM AUTHOR]

Herein we have discussed such important modified rhodamine compounds which have been used as chemosensors for the last 7–8 years. This review covered some chemosensors for the detection of metal ions like Al(III), Cu(II), Hg(II), Co(II), Fe(III), Au(III), Cr(III), and some anion like CN−. The selectivity, sensitivity, photophysical properties (i.e., UV–Vis spectral studies, fluorescence studies giving special emphasis to absorption wavelength in UV–Vis spectra and excitation and emission wavelength in fluorescence spectra), binding affinity, the limit of detection, and the application of those chemosensors are described clearly. Here we have also discussed some functionalized rhodamine-based chemosensors that emit in the near-infrared region (NIR) and can target lysosomes and detect lysosomal pH. Their versatile applicability in the medicinal ground is also delineated. We have focused on the photophysical properties of spirolactam rhodamine photoswitches and applications in single-molecule localization microscopy and volumetric 3D light photoactivable dye displays. The real-time detection of radical intermediates has also been exemplified. [ABSTRACT FROM AUTHOR]

A new colorimetric and fluorescence turn‐on chemodosimeter for selective detection of GSH over Cys and Hcy with 34‐fold enhancement in emission intensity is reported. Probe 1 exhibited ultra‐sensitivity toward GSH with 0.125 nM detection limit and successfully displayed GSH detection in MCF‐7 live cells. The mechanism of sensing is established by density functional theoretical calculations. [ABSTRACT FROM AUTHOR]

Aim. Carbon particles have been widely used in different technologies and have great potential for new biological application. Synthesis of carbon particles from agricultural waste using “green” principles is in the mainstream of biotechnology area and attract a great attention in biomedical application. Here, coarse carbon particles (CCPs) were synthesized using “green” principles from dry apple and used in the biological experiments without preliminary functionalization. Methods. Neurotoxic features of CCPs were analysed in isolated presynaptic cortex nerve terminals (synaptosomes) monitoring the extracellular levels of excitatory neurotransmitter L-[14C] glutamate and inhibitory one [3H]GABA, as well as the membrane potential. Results. Measuring the membrane potential of the nerve terminals, it was revealed an inadequate decrease in the fluorescence intensity of the potential-dependent dye rhodamine 6G in the presence of CCPs (1 mg/ml). This decrease was not due to membrane hyperpolarisation because CCPs did not change the extracellular synaptosomal levels of L-[14C] glutamate and [3H]GABA. CCP-induced decrease in the fluorescence intensity of the dye in nerve terminals can be due to its interaction with CCPs. Indeed, the ability of CCPs to interact with rhodamine 6G was shown in synaptosome-free incubation media. Conclusions. Therefore, CCPs did not possess neurotoxic signs, and so are biocompatible. In both experiments, i.e. without bio object and in biological system, CCPs were able to interact with fluorescent dye rhodamine 6G. In prospect, this feature of CCPs can be used in biotechnology after further investigation of dye interaction conditions.

Abstract There is a claimed increase in the global prevalence and incidence of emerging diseases observed in many organisms. Myxozoa represents an essential group of metazoan parasites that hold both economic and ecological significance. In the current study, 1% of the fish population at two commercial goldfish (Carassius auratus) farms in Tehran and Ghom province, Iran, developed cavitating muscular lesions resembling humps in February 2021 and January 2022. Fish displaying pathological abnormalities were transported to the Ornamental Fish Clinic and subjected to clinical examination. Light microscopy was subsequently used to examine wet smears of skin and gills, as well as whitish exudate. In addition, tissue homogenates were collected for more precise identification and molecular confirmation. The study discovered that individuals from the goldfish farms were infected with the pathogenic myxozoan Myxobolus lentisuturalis, which caused significant damage to the epaxial muscles. The spores collected from the humps had a lack of uniformity and were primarily ellipsoidal in shape. Histopathological analysis also revealed parasites in various stages of development, such as plasmodia and spores, as well as inflammatory cell infiltration (macrophage, giant cell and lymphoplasmacytic infiltration) between skeletal muscle fibers. Phylogenetic analysis of M. lentisuturalis was performed by using MEGA 11 and the maximum likelihood method. M. lentisuturalis is a myxozoan parasite that has been sparsely recorded and lacks widespread recognition. The current study is the first clinical, histopathological, and molecular characterization of M. lentisuturalis isolated from the skeletal musculature of goldfish (C. auratus) in Iran.

In this study, the new solid lipid nanoparticles were created by combining fluorescent dye, fatty acid, lipid, and bacterial outer membranes. The synthesised particles were roughly 95–100 nm in size. Vero cells cultivated with these nanoparticles showed no cytotoxicity in 5-dimethylthiazol-2-yl-2, 5-diphenyltetrazolium bromide (MTT) assay. In the cell uptake studies, the vero cell line was employed. Cell lines absorbed fluorescent solid lipid nanoparticles (FSL NPs) better, according to the findings. The confocal microscopy results revealed a significant accumulation of FSL NPs in the cytoplasm over time. The results of small animal imaging employing BALB/c mice revealed that the nanoparticles generated provided high contrast signals. Overall, the OMVs-based FSL NPs system offers a unique imaging tool for studying intracellular interactions as well as a viable tool for drug delivery. [ABSTRACT FROM AUTHOR]

The mechanochromic materials can respond to environmental changes by altering the optical properties of the system, which has garnered significant attention in recently. The utilization of these materials for the purpose of sensing tensile and compressive stress has been extensively documented. However, the mechanochromic polymer that can effectively discriminate hardness of inorganic particles is still rarely reported. In this article, a force‐sensitive organic polysiloxane was developed by introducing triethenyl‐substituted rhodamine derivatives crosslinker into the polymethylhydrosiloxane network through hydrosilylation addition reaction. The results demonstrated that the grinding of the crosslinked polysiloxane effectively facilitated the transmission of external force to the polymeric network, leading to an open ring isomerization of rhodamine accompanied by significant alterations in visible and fluorescent color. In addition, we found that the optical properties of the system showed distinct variations when the inorganic particles with different Moh's hardness were co‐ground with the polysiloxane. High Moh's hardness particles, such as Al2O3, could effectively trigger the mechanochromic behavior of the polymer, while Na2SO4 particles with low hardness failed to induce the corresponding change. Therefore, this organic polysiloxane could be used as a potential fluorescent indicator for hardness recognition. [ABSTRACT FROM AUTHOR]

Various techniques are available to illuminate geometric structures of molecular ions in gas phase, such as Förster Resonance Energy Transfer (FRET) informing on distances between two dyes covalently attached to a molecule. Typically, cationic rhodamines, which absorb and emit visible light, are used for labeling. Extensive work has revealed that the transition energy of a rhodamine is intricately linked to its nearby microenvironment, with nearby charges causing Stark‐shifted emission. This occurs because the inter‐dye Coulomb interaction is weaker in the excited state (S1) than in the ground state (S0) due to the increase in polarizability upon excitation. Therefore, absorption and emission spectra, along with FRET efficiencies, provide insights into structural motifs. At room temperature, multiple conformers often co‐exist, leading to overlapping absorption bands among different conformers and broad spectra. To study specific conformers, it is necessary to isolate them, for example, using ion‐mobility spectrometry. Another approach is to reduce temperature, which results in spectral narrowing and distinct absorption bands, allowing for the selection of specific conformers through selective excitation. Here, we describe the instrumentation used for cryogenically cold FRET experiments and discuss recent results for small model systems, as well as future directions for a technique still in its infancy. [ABSTRACT FROM AUTHOR]

Mechanochromic materials have received broad research interests recently, owing to its ability to monitor the in situ stress/strain in polymer materials in a straightforward way. However, one major setback that hinders the practical application of these materials is their low sensitivity toward tensile strain. Here a new strategy for pre‐stretching of the mechanochromic agent in a polymer film on the molecular scale, which can effectively enhance the mechanochromic sensitivity of a polymer film toward tensile strain, is shown. In situ fluorescent measurement during tensile test shows an early activation of the mechanochromic agent at tensile strain as low as 50%. The pre‐stretching effect is realized by first inducing ring‐opening of the mechanochromic agent by molecular functionalization, and then compelling the ring‐closure process in the cured film by elevated temperature. This post‐curing ring‐closure process will result in pre‐stretched mechanochromic agent in a crosslinked network. The mechanism for mechanochromic activation of polymer films with different composition is elaborated by visco‐elastic measurements, and the effect of pre‐stretching is further confirmed by films with other compositions. Combined with the simplicity of the method developed, this work could offer an alternative strategy to enhance the sensitivity of different mechanochromic agents toward tensile strain. [ABSTRACT FROM AUTHOR]

In environmental studies, rhodamine dyes are commonly used to trace water movements and pollutant dispersion. Remote sensing techniques offer a promising approach to detecting rhodamine and estimating its concentration, enhancing our understanding of water dynamics. However, research is needed to address more complex environments, particularly optically shallow waters, where bottom reflectance can significantly influence the spectral response of the rhodamine. Therefore, this study proposes a novel approach: transferring pre-trained classifiers to develop a generalizable method across different environmental conditions without the need for in situ calibration. Various samples incorporating distilled and seawater on light and dark backgrounds were analyzed. Spectral analysis identified critical detection regions (400–500 nm and 550–650 nm) for estimating rhodamine concentration. Significant spectral variations were observed between light and dark backgrounds, highlighting the necessity for precise background characterization in shallow waters. Enhanced by the Sequential Feature Selector, classification models achieved robust accuracy (>90%) in distinguishing rhodamine concentrations, particularly effective under controlled laboratory conditions. While band transfer was successful (>80%), the transfer of pre-trained models posed a challenge. Strategies such as combining diverse sample sets and applying the first derivative prevent overfitting and improved model generalizability, surpassing 85% accuracy across three of the four scenarios. Therefore, the methodology provides us with a generalizable classifier that can be used across various scenarios without requiring recalibration. Future research aims to expand dataset variability and enhance model applicability across diverse environmental conditions, thereby advancing remote sensing capabilities in water dynamics, environmental monitoring and pollution control. [ABSTRACT FROM AUTHOR]

There is a claimed increase in the global prevalence and incidence of emerging diseases observed in many organisms. Myxozoa represents an essential group of metazoan parasites that hold both economic and ecological significance. In the current study, 1% of the fish population at two commercial goldfish (Carassius auratus) farms in Tehran and Ghom province, Iran, developed cavitating muscular lesions resembling humps in February 2021 and January 2022. Fish displaying pathological abnormalities were transported to the Ornamental Fish Clinic and subjected to clinical examination. Light microscopy was subsequently used to examine wet smears of skin and gills, as well as whitish exudate. In addition, tissue homogenates were collected for more precise identification and molecular confirmation. The study discovered that individuals from the goldfish farms were infected with the pathogenic myxozoan Myxobolus lentisuturalis, which caused significant damage to the epaxial muscles. The spores collected from the humps had a lack of uniformity and were primarily ellipsoidal in shape. Histopathological analysis also revealed parasites in various stages of development, such as plasmodia and spores, as well as inflammatory cell infiltration (macrophage, giant cell and lymphoplasmacytic infiltration) between skeletal muscle fibers. Phylogenetic analysis of M. lentisuturalis was performed by using MEGA 11 and the maximum likelihood method. M. lentisuturalis is a myxozoan parasite that has been sparsely recorded and lacks widespread recognition. The current study is the first clinical, histopathological, and molecular characterization of M. lentisuturalis isolated from the skeletal musculature of goldfish (C. auratus) in Iran. [ABSTRACT FROM AUTHOR]

Rhodamine dyes have been extensively explored for bioimaging and therapeutic applications over the past few decades. However, it remains a challenge to design long‐wavelength and large Stokes shift rhodamine derivatives to meet the requirements of fluorescence imaging and phototherapy in deep living tissues. In this work, a pyridine aromatic unit was inserted into the rhodamine derivatives (AC‐Fluor: ACF) skeleton to prepare a series of stable rhodamine derivatives, named ACFPs, to achieve long emission wavelength (>650 nm) and large Stokes shift (~60 nm) by tuning the conjugated systems and electronic symmetry. Moreover, ACFPs are capable of continuously producing superoxide radical (O2−⋅) under long wavelength irradiation. This study presents a novel paradigm for improving the optical properties of rhodamine, which has led to the development of a novel tool for image‐guided phototherapy for cancer treatment. [ABSTRACT FROM AUTHOR]

Aim. Carbon particles have been widely used in different technologies and have great potential for new biological application. Synthesis of carbon particles from agricultural waste using "green" principles is in the mainstream of biotechnology area and attract a great attention in biomedical application. Here, coarse carbon particles (CCPs) were synthesized using "green" principles from dry apple and used in the biological experiments without preliminary functionalization. Methods. Neurotoxic features of CCPs were analysed in isolated presynaptic cortex nerve terminals (synaptosomes) monitoring the extracellular levels of excitatory neurotransmitter L-[14C] glutamate and inhibitory one [3 H]GABA, as well as the membrane potential. Results. Measuring the membrane potential of the nerve terminals, it was revealed an inadequate decrease in the fluorescence intensity of the potential-dependent dye rhodamine 6G in the presence of CCPs (1 mg/ml). This decrease was not due to membrane hyperpolarisation because CCPs did not change the extracellular synaptosomal levels of L-[14C] glutamate and [³H]GABA. CCP-induced decrease in the fluorescence intensity of the dye in nerve terminals can be due to its interaction with CCPs. Indeed, the ability of CCPs to interact with rhodamine 6G was shown in synaptosome-free incubation media. Conclusions. Therefore, CCPs did not possess neurotoxic signs, and so are biocompatible. In both experiments, i.e. without bio object and in biological system, CCPs were able to interact with fluorescent dye rhodamine 6G. In prospect, this feature of CCPs can be used in biotechnology after further investigation of dye interaction conditions. [ABSTRACT FROM AUTHOR]

Modern industry actively uses metal structural materials to create innovative devices and components. In order to prevent emergency situations in production, nondestructive testing methods are used to detect defects on the surface of the material being developed. Among the methods of nondestructive testing, one can highlight the method of luminescent magnetic flaw detection, which allows identifying defects on the surface and under the surface of the test sample with minimal effort. It is known that in some cases, the magnetic‐powder method cannot achieve the required sensitivity due to the shape and location of defects themselves or due to certain conditions of object operation. To increase the visibility and sensitivity, magnetic nano‐ and microparticles can be conjugated with the dyes. Iron oxide nanoparticles (Fe3O4, γ‐Fe2O3) can be used as such magnetic particles, since they are quite easy to obtain and have low toxicity, high chemical stability, and a wide variety of magnetic properties. To ensure fluorescence of magnetic particles, a wide variety of fluorescent dyes associated with such particles are used. The dyes can include morin, naphthalimide derivatives, as well as semiconductor quantum dots. This article provides a review of fluorescent composite micro‐ and nanoparticles based on xanthene dyes (rhodamine, fluorescein, and pyronine). Such dyes are economically available luminophores, have good binding to the surface of magnetic particles, and therefore can be suitable for luminescent magnetic flaw detection. This review article discusses methods for producing composite nano‐ and microparticles of iron oxides with xanthene dyes and provides prospects of using composite nano‐ and microparticles in nondestructive testing methods. [ABSTRACT FROM AUTHOR]

Mechanophoric polymers are an interesting class of smart polymers which contains a special force‐sensitive molecular motif that can lead to a chemical change within the polymer network in response to mechanical force. This investigation reports the design of a mechanophoric polymer based on epoxy‐functionalized rhodamine via a monomeric approach. In this case, rhodamine (Rh) is modified with glycidyl methacrylate (GMA) through an epoxy–amine reaction to design a vinyl‐functionalized multi‐armed macromonomer (Rh‐GMA), which is reacted with butyl acrylate (BA) to prepare the crosslinked polymeric film. The crosslinked polymeric film demonstrates mechanophoric properties under UV and stretching conditions. [ABSTRACT FROM AUTHOR]

Nonlinear photochromic reactions that work with weak incoherent light are important for molecular operations with high spatial resolution and multiple photofunctions based on single molecules. However, nonlinear photochromic compounds generally require complex molecular design, restricting accessibility in various fields. Herein, we report nonlinear photochromic properties in a perylene‐substituted rhodamine spirolactam derivative (Rh−Pe), which is synthesized from rhodamine B in facile procedures. Direct excitation of Rh−Pe produces the triplet excited state via the charge‐transfer (CT) state. The triplet excited state causes triplet–triplet annihilation to bring the generation of the intensely colored ring‐open form with nonlinear behavior. Furthermore, green‐ and red‐light‐induced photochromism was achieved in Rh−Pe using triplet sensitizers, although Rh−Pe can be directly excited only by ultraviolet and blue light. Our findings are expected to contribute to the development of photofunctional materials showing nonlinear behavior and low‐energy light responsivity. [ABSTRACT FROM AUTHOR]

During a stress condition, the human body synthesizes catecholamine neurotransmitters and specific hormones (called "stress hormones"), the most important of which is cortisol. The monitoring of cortisol levels should be extremely important to control the stress levels, and for this reason, it shows important medical applications. The common analytical methods (HPLC, GC‐MS) cannot be used in real life, due to the bulky size of the instruments and the necessity of specialized personnel. Molecular probes solve these problems due to their fast and easy use. The synthesis of new fluorescent rhodamine probes, able to interact by non‐covalent interactions with cortisol, the recognition properties in solution as well as in solid state by Strip Test, using a smartphone as detector, are here reported. DFT calculations and FT‐IR measurements suggest the formation of supramolecular complexes through hydrogen bonds as main non‐covalent interaction. The present study represents one of the first sensor, based on synthetical chemical receptors, able to detect cortisol in a linear range from 1 mM to 1 pM, based on non‐covalent molecular recognition and paves the way to the realization of practical point‐of‐care device for the monitoring of cortisol in real live. [ABSTRACT FROM AUTHOR]

Mitochondria-targeted antioxidants (MTAs) have been studied quite intensively in recent years as potential therapeutic agents and vectors for the delivery of other active substances to mitochondria and bacteria. Their most studied representatives are MitoQ and SkQ1, with its fluorescent rhodamine analog SkQR1, a decyl ester of rhodamine 19 carrying plastoquinone. In the present work, we observed a pronounced antibacterial action of SkQR1 against Gram-positive bacteria, but virtually no effect on Gram-negative bacteria. The MDR pump AcrAB-TolC, known to expel SkQ1, did not recognize and did not pump out SkQR1 and dodecyl ester of rhodamine 19 (C12R1). Rhodamine 19 butyl (C4R1) and ethyl (C2R1) esters more effectively suppressed the growth of ΔtolC Escherichia coli, but lost their potency with the wild-type E. coli pumping them out. The mechanism of the antibacterial action of SkQR1 may differ from that of SkQ1. The rhodamine derivatives also proved to be effective antibacterial agents against various Gram-positive species, including Staphylococcus aureus and Mycobacterium smegmatis. By using fluorescence correlation spectroscopy and fluorescence microscopy, SkQR1 was shown to accumulate in the bacterial membrane. Thus, the presentation of SkQR1 as a fluorescent analogue of SkQ1 and its use for visualization should be performed with caution. [ABSTRACT FROM AUTHOR]

This study explores the impact of incorporating oxyethylene (OE) chains into rhodamine‐based dye molecules for the enhancement of photophysical properties in the context of chemical sensing. The introduction of OE chains provides several advantages, including improved water solubility, photostability and resistance to self‐assembled nanoaggregates formation. Despite these, the compound with oxyethylene chains showed poor response (~2‐fold) towards Hg2+ ions than that of dimeric probe (~20 fold) with no such substituents. Notably, dimeric compound shows a remarkable three‐fold larger response to Hg2+ ion compared to monomeric compound. This intriguing outcome is attributed to the extended conjugation within the dimeric structure, which can induce conformational change of the overall molecule. Moreover, the study investigates the effects of end substituents, such as electron‐donating (−OMe, improved response) and electron‐withdrawing (−NO2, poor response) groups, on the interaction with Hg2+ ions. The excellent sensitivity of the probe molecules is also evident in significantly low detection limits for Hg2+ ion (5–8 ppb) in real‐life water samples. The high recovery values (>95 %) with sufficient low standard deviation (<5%) indicates that quantitative analysis of Hg2+ is achievable using the current protocol. Beyond that, we have employed the probe 1 for intracellular (HEK293T cells) fluorescence imaging of Hg2+. [ABSTRACT FROM AUTHOR]

Iron, as the most prevalent critical trace element in the human body, is crucial for many basic physiological functions and has many environmental applications. Therefore, excellent chemosensors with high sensitivity and good selectivity toward iron are highly desired. Three new fluorescent colorimetric chemosensors (CS1, CS2, and CS3) were synthesized and prepared through a one-step reaction to selectively detect Fe3+ in aqueous media. To effectively coordinate metal ions, the sensors contain rhodamine derivatives with different "N, O" donor atoms. Of these sensors, CS2 and CS3 demonstrated sensing behavior and colorimetric "off–on" sensing for Fe3+ over various biologically important metal ions, rendering good selectivity. Fluorescent imaging was performed to confirm the possibility of applying the sensors in living cells. [ABSTRACT FROM AUTHOR]

In this study, the primary objective is to synthesize a novel fluorescent Rh‐PP‐Rh compound and explore its extensive range of photochemical behaviors. Initially, the synthesis of the novel Rh‐PP‐Rh was carried out for this purpose. Subsequently, UV‐Vis and fluorescence spectroscopy were employed to investigate the interactions between Rh‐PP‐Rh and a diverse array of ions in aqueous solvent systems. Through fluorescence and UV‐Vis studies, it was observed that Rh‐PP‐Rh demonstrated turn‐on sensor properties in the presence of Hg2+ ions. Furthermore, the limits of detection (LOD) and association constant (Ka) values for Rh‐PP‐Rh/Hg2+ were determined as 334 nM and 9.13×1011 M−2, respectively. Additionally, the reversible studies demonstrated a switchable on/off response upon alternate addition of HgCl2 and [Bu4N]F to Rh‐PP‐Rh. These findings suggest that the probe Rh‐PP‐Rh also possesses specific sensor properties for F− ions in the presence of mercury. In addition, the investigation encompassed an assessment of the visual analysis of the color alterations of Rh‐PP‐Rh both on filter paper and in an EtOH/H2O solution. The findings demonstrated that Rh‐PP‐Rh can be successfully utilized in solutions containing mercury, as it generates significant color transformations. [ABSTRACT FROM AUTHOR]

Recent advancements in the field of photoresponsive-based mercury (II) sensors have witnessed a surge in research focused on enhancing detection capabilities. Leveraging innovations in materials science, particularly with quantum dots, nanomaterials, and organic semiconductors, these sensors exhibit improved selectivity and sensitivity. Beyond traditional applications, such as environmental monitoring, the integration of photoresponsive principles with emerging technologies like the internet of things (IoT) and wearable promises real-time and remote mercury (II) ion detection. The on-going efforts also explore multifunctional sensors and miniaturization for on-site applications, addressing current challenges and paving the way for broader commercialization. This dynamic landscape underscores the potential for these sensors to play a crucial role in ensuring the effective monitoring and management of mercury (II) levels in diverse settings.

A novel platform of a polydiacetylene combined with rhodamine B (PDA-Rho) colorimetric chemosensor array was prepared from a diacetylene monomer and rhodamine B derivative. Rhodamine B derivative as the ion-recognition element was embedded in the polydiacetylene matrix. To fabricate chemosensor, diacetylene monomer connected rhodamine B derivatives (DA-Rho) was coated onto a filter paper surface via drop-casting technique and transformed to polydiacetylene by polymerisation through ultraviolet (UV) irradiation. From the result, PDA-Rhoen exhibited high sensitivity and selectivity for Au3+ and could be monitored directly by naked eyes providing a fast, portable and easy-to-use as a molecular device in the real system. The DFT calculation results showed a stable complex between PDA-Rho and Au3+. We believe that, this method offers a sensitive and accurate process for Au3+ ion detection in real environmental and biological applications. [ABSTRACT FROM AUTHOR]

This study describes the development of a fast and cost-effective method for the detection and removal of Hg2+ ions from aqueous media, consisting of hydrogels incorporating chelating agents and a rhodamine derivative (to afford a qualitative evaluation of the heavy metal entrapment inside the 3D polymeric matrix). These hydrogels, designed for the simultaneous detection and entrapment of mercury, were obtained through the photopolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) and N-vinyl-2-pyrrolidone (NVP), utilizing N,N′-methylenebisacrylamide (MBA) as crosslinker, in the presence of polyvinyl alcohol (PVA), a rhodamine B derivative, and one of the following chelating agents: phytic acid, 1,3-diamino-2-hydroxypropane-tetraacetic acid, triethylenetetramine-hexaacetic acid, or ethylenediaminetetraacetic acid disodium salt. The rhodamine derivative had a dual purpose in this study: firstly, it was incorporated into the hydrogel to allow the qualitative evaluation of mercury entrapment through its fluorogenic switch-off abilities when sensing Hg2+ ions; secondly, it was used to quantitatively evaluate the level of residual mercury from the decontaminated aqueous solutions, via the UV-Vis technique. The ICP-MS analysis of the hydrogels also confirmed the successful entrapment of mercury inside the hydrogels and a good correlation with the UV-Vis method. [ABSTRACT FROM AUTHOR]

Detection of correct oxidation state of a metal ion is important to understand its speciation and redox properties. Some of rhodamine derivatives can identify Al3+, Cr3+ and Fe3+ as the trivalent cations. We have synthesized a rhodamine derivative, HL‐qui, from the reaction of N‐(rhodamine‐6G)lactam‐ethylenediamine with quinoline‐2‐carboxaldehyde for the colorimetric as well as fluorogenic detection of all of metal ions with +3 oxidation state such as Al3+, Cr3+, Fe3+, Ga3+, In3+, Tl3+ and Gd3+. In the presence of these trivalent cations, colorless and nonfluorescent HL‐qui turns pink and strongly fluorescent in HEPES buffer (10 mM) in H2O/ethanol=1/9 (v/v) (pH 7.4) as its spirolactam ring gets open to show the changes in color and fluorescence properties. High sensitivity of the probe towards the cations is reflected from the limit of detection values that are in nM range. To the best of our knowledge, there is no such report where fluorescence sensing has been utilized to determine oxidation state. This multi‐ion sensing feature has been used for fabrication of multi input‐output based logic circuit using Boolean algebraic method. It has been used in imaging of metal ions in living cell (L6 cells). [ABSTRACT FROM AUTHOR]

Thiazolidin-4-ones have a broad range of medical and clinical implementation, which is important for pharmaceutical and medicinal chemistry. This heterocyclic core has been reported to possess a diversity of bioactivities, including antimicrobial and antibiofilm-forming potential. The resistance of biofilms to antibiotics or disinfectants is a serious medical problem. Therefore, there is a natural need to discover new effective structures with properties that inhibit biofilm formation. This review aims to analyze the antibiofilm features of thiazolidin-4-ones described in the literature over the last two decades. The information gathered in this review could benefit the rational design of new effective antibiofilm small molecules with thiazolidin-4-one cores. [ABSTRACT FROM AUTHOR]

Rhodamine-based chemosensors have sparked considerable interest in recent years due to their remarkable photophysical properties, which include high absorption coefficients, exceptional quantum yields, improved photostability, and significant red shifts. This article presents an overview of the diverse fluorometric, and colorimetric sensors produced from rhodamine, as well as their applications in a wide range of fields. The ability of rhodamine-based chemosensors to detect a wide range of metal ions, including Hg+2, Al3+, Cr3+, Cu2+, Fe3+, Fe2+, Cd2+, Sn4+, Zn2+, and Pb2+, is one of their major advantages. Other applications of these sensors include dual analytes, multianalytes, and relay recognition of dual analytes. Rhodamine-based probes can also detect noble metal ions such as Au3+, Ag+, and Pt2+. They have been used to detect pH, biological species, reactive oxygen and nitrogen species, anions, and nerve agents in addition to metal ions. The probes have been engineered to undergo colorimetric or fluorometric changes upon binding to specific analytes, rendering them highly selective and sensitive by ring-opening via different mechanisms such as Photoinduced Electron Transfer (PET), Chelation Enhanced Fluorescence (CHEF), Intramolecular Charge Transfer (ICT), and Fluorescence Resonance Energy Transfer (FRET). For improved sensing performance, light-harvesting dendritic systems based on rhodamine conjugates has also been explored for enhanced sensing performance. These dendritic arrangements permit the incorporation of numerous rhodamine units, resulting in an improvement in signal amplification and sensitivity. The probes have been utilised extensively for imaging biological samples, including imaging of living cells, and for environmental research. Moreover, they have been combined into logic gates for the construction of molecular computing systems. The usage of rhodamine-based chemosensors has created significant potential in a range of disciplines, including biological and environmental sensing as well as logic gate applications. This study focuses on the work published between 2012 and 2021 and emphasises the enormous research and development potential of these probes. [ABSTRACT FROM AUTHOR]

Metals are extensively used for different applications in agriculture and industry. Accumulations of these metals in the environment lead to serious health concerns. Currently, fast and accurate detection of metal ions in the environment or biological system has become a critical issue. Hence, developing an appropriate tool for the detection of metals can help reduce environmental metal pollution and reduce health concerns. In the present study, a hybrid fluorescent probe or chemosensor for parallelly detecting two important metal ions (Mercury and Aluminium) has been designed and tested for its detection efficiency. The newly synthesized chemosensor 3′,6′-bis(ethylamino)-2′,7′-dimethyl-3H-spiro[isobenzofuran-1,9′-xanthen]-3-one (RS) was found to specifically detect Hg2+ and Al3+ ions with high sensitivity and selectivity. The chemical and physical properties of chemosensor RS were tested using single-crystal X-ray diffraction, UV and Fluorescence analysis. The quick response to Hg2+ and Al3+ is attributable to the creation of a coordinate bond present between the chemosensor RS and the metal ion. The selective sensing of chemosensor RS is due to the spirolactam ring opening followed by the development of proper coordinate geometry in the chemosensor. 1H NMR titration experiment and Job’s approach studies suggest a significant binding stoichiometry between the chemosensor RS and the metal ions at a 1:1 ratio. The limit of detection (LOD) of chemosensor RS was determined to be 1.88 µM for Al3+ and 1.75 µM for Hg2+ ions. The in vivo studies using two experimental animal models, Drosophila melanogaster (fruit fly) and Poecilia reticulate (guppy fish), clearly demonstrate its efficiency in detecting endogenously absorbed Hg2+ and Al3+. Thus, chemosensor RS can selectively and simultaneously detect Hg2+ and Al3+ in biological or environmental samples and can help us in monitoring metal leaching into the environment.

In environmental studies, rhodamine dyes are commonly used to trace water movements and pollutant dispersion. Remote sensing techniques offer a promising approach to detecting rhodamine and estimating its concentration, enhancing our understanding of water dynamics. However, research is needed to address more complex environments, particularly optically shallow waters, where bottom reflectance can significantly influence the spectral response of the rhodamine. Therefore, this study proposes a novel approach: transferring pre-trained classifiers to develop a generalizable method across different environmental conditions without the need for in situ calibration. Various samples incorporating distilled and seawater on light and dark backgrounds were analyzed. Spectral analysis identified critical detection regions (400–500 nm and 550–650 nm) for estimating rhodamine concentration. Significant spectral variations were observed between light and dark backgrounds, highlighting the necessity for precise background characterization in shallow waters. Enhanced by the Sequential Feature Selector, classification models achieved robust accuracy (>90%) in distinguishing rhodamine concentrations, particularly effective under controlled laboratory conditions. While band transfer was successful (>80%), the transfer of pre-trained models posed a challenge. Strategies such as combining diverse sample sets and applying the first derivative prevent overfitting and improved model generalizability, surpassing 85% accuracy across three of the four scenarios. Therefore, the methodology provides us with a generalizable classifier that can be used across various scenarios without requiring recalibration. Future research aims to expand dataset variability and enhance model applicability across diverse environmental conditions, thereby advancing remote sensing capabilities in water dynamics, environmental monitoring and pollution control.

The photoresponsive nature of the triazole sensors introduces a dynamic element to biomaterial sensing, enabling precise control and modulation of their response. The investigation explores the innovative application of triazole sensors with photoresponsive properties in biomaterial sensing. Combining the robust binding capabilities of the triazole scaffold with the adaptability conferred by photoresponsive units, these sensors introduce a dynamic element to sensing, enabling precise control and modulation of their response. The study showcases their versatility in various applications, from cellular imaging to biomarker monitoring, within complex biological environments. Through customization based on specific biomolecules of interest, the sensors exhibit high selectivity, making them valuable tools for unraveling cellular processes and disease mechanisms. Activity testing likely involved synthesizing and characterizing these sensors and evaluating their performance through techniques such as spectroscopy, microscopy, and biochemical assays. The results underscore the transformative potential of photoresponsive-based triazole sensors in advancing biomaterials sensing technologies, with implications for diagnostics, drug discovery, and fundamental biological research. Overall, the investigation emphasizes their adaptability and versatility in addressing the evolving landscape of biological sensing challenges.

Fluorescent probes play a crucial role in analytical chemistry and biological imaging, offering selective detection of metal ions. Herein, we present the synthesis and characterization of a novel rhodamine-based fluorescent probe, RbHC (Rhodamine B Helicin), which was obtained through the condensation of rhodamine B hydrazide and helicin in ethanol. The probe demonstrates remarkable selectivity and anti-interference capabilities towards Cu2+ and Fe3+ ions in 80% acetonitrile solution. Spectral titration analysis revealed a linear relationship between the intensity and the concentration of Cu2+/Fe3+. The formation of complex between Cu2+/Fe3+ and RbHC was confirmed to be 1:1, and it was further confirmed by ESI mass spectroscopy and DFT calculations. The coordination with Cu2+/Fe3+ caused the opening of RbHC's spirolactam ring, resulting in distinct color change and red fluorescence emissions. Moreover, RbHC exhibits high stability and water solubility under both acidic and neutral conditions, enabling its application in the imaging of plant tissues. Besides, the absorption intensity of RbHC–Cu2+ increased significantly when exposed to sunshine and 365 nm UV radiation, indicating that it might be used as a potential indicator for measuring outdoor UV intensity.

In this study, we have successfully synthesised a novel fluorescent chemosensor TM using rhodamine as the fluorophore and 8-hydroxyquinoline as recognition group through traditional Schiff base preparation methods. The chemical structure of sensor TM was characterised by 1H NMR, 13C NMR and ESI-MS. Sensor TM showed obvious fluorescence enhancement response to Hg2+ ion. The detection limit was 0.05 μM, and the solution colour changed from colourless to pink, making it a promising probe for effective naked-eye detection of Hg2+. The results of Job curve indicated that sensor TM and Hg2+ ion coordinated with each other with a binding stoichiometry of 1:1, and the pH test results showed that sensor TM was only suitable for acidic and neutral conditions. [ABSTRACT FROM AUTHOR]

With the demand for the diversity and security of information deliveries increasing, advanced security tag for data encryption has attracted great interest from the scientific community. It is promising to achieve composite dynamic information storage by the combination of multisource stimuli‐responsive mechanism. Here, mechano‐ and chemochromism cholesteric liquid crystal elastomers (CLCEs) are prepared by introducing a rhodamine lactam‐based functional trigger by two different strategies, one of which is one‐pot method and another is postfunctionalization method. The performances of the CLCEs from two strategies are investigated, which are demonstrated to be effective methods in endowing material with new function, and suitable for different application scenarios. The composite material combines the force‐induced structural periodicity variation of CLCE and the pigmentary and fluorescent properties changes of the functional trigger caused by the chemical environment. The orthogonal construction of dynamic structural color pattern and reversible pigmentary and fluorescent colors pattern enable the information in the CLCE to display double encryption mode, which exhibits great potential in the information storage and anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Rhodamine, which is extensively used as a synthetic dye in food industry, is regarded as an illegal additive by European Food Safety Authority because of its carcinogenic and toxicological properties. Since it's a colourless material at low concentrations such as 10-7 M, its detection via spectroscopical methods is very challenging and crucial in terms of food safety issues. In this study Ag nanowires were synthesized, their crystal structure is characterized via XRD analysis, their surface morphology and radius are determined via SEM images and their chemical composition was determined by EDS analysis. Afterwards, rhodamine solutions which were prepared at 10-4 - 10-7 M were dropcasted onto Ag nanowire solutions. After selecting three characteristic Raman peaks belonging to the Rhodamine molecule, which are located at 612, 1189 and 1362 cm-1, detection of Rhodamine was performed at these ultra low concentrations. As a result, one can conclude that Ag nanowires can be utilized as possible SERS substrates for detection of Rhodamine at low concentrations by exhibiting significant reproducibility, stability and recyclability features. [ABSTRACT FROM AUTHOR]

In this work, silver nanowires are embedded in a polymer waveguide doped with Rhodamine 6 G. The waveguides are constructed around selected isolated nanowires using electron beam lithography. A probe laser is focused at one end of the waveguide that launches surface plasmons polaritons in the silver nanowire. An additional low-powered 5 W/cm 2 pump laser is focused on top of the nanowire to pump the Rhodamine. A 75 cm - 1 gain is measured in the polymer waveguide. The plasmon scattered at the other end of the nanowire is imaged with a CCD camera and an amplified photodetector. Comparing images with and without pumping shows an increase in the intensity of the scattered plasmon. The photodetector signal from the end of the nanowire is passed through a lock-in amplifier and gives an average increase of 3.2% with pumping. This shows a partial compensation of the losses in plasmon propagation and increases in their propagation length. [ABSTRACT FROM AUTHOR]

Rhodamine dyes, as star molecules of fluorescent dyes, are critical tools in modern analytical and biochemical research. However, switching their chiroptical properties still remains a big challenge because of the absence of a suitable synthesis method to incorporate through conjugation a chiral fragment into the chromophore core of rhodamine. Herein, a simple and straightforward way is utilized to link two rhodamine chromophores by different chiral bridges. The conjugated RRR/SSS birhodamine dyes with one axial chirality, which is constructed directly by two rhodamine chromophores, and two spirocyclic chiralities show the interesting circular dichroism and circularly polarized luminescence switching and lysosome‐targetable properties. On the other hand, the unconjugated RR/SS birhodamine dyes with two chiral carbons do not have such chiroptical switching properties but do have different amazing cellular staining properties. The RR birhodamine dye can stain both lysosomes and mitochondria, but SS birhodamine dye can stain lysosomes only. Moreover, the mechanisms of chiroptical switching and diastereoselectivity are investigated as well, based on single‐crystal structures and density functional theory calculations. Therefore, a new platform is afforded here in designing chiral dyes for chiroptical switching and cell imaging applications. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) has recently become significant as a clinical modality for cancer therapy and multidrug-resistant (MDR) infections, replacing conventional chemotherapy and radiation therapy protocols. PDT involves the excitation of certain nontoxic molecules called photosensitizers (PS), applying a specific wavelength of light to generate reactive oxygen species (ROS) to treat cancer cells and other pathogens. Rhodamine 6G (R6G) is a well-known laser dye with poor aqueous solubility, and lower sensitivity poses an issue in using PS for PDT. Nanocarrier systems are needed to deliver R6G to cancer targets since PDT requires a higher accumulation of PS. It was found that R6G-conjugated gold nanoparticles (AuNP) have a higher ROS quantum yield of 0.92 compared to 0.3 in an aqueous R6G solution, increasing their potency as PS. Cytotoxicity assessment on A549 cells and antibacterial assay on MDR Pseudomonas aeruginosa collected from a sewage treatment plant are the evidence to support efficient PDT. In addition to their enhanced quantum yields, the decorated particles are effective in generating fluorescent signals that can be used for cellular imaging and real-time optical imaging, and the presence of AuNP is a valuable addition to CT imaging. Furthermore, the fabricated particle exhibits anti-Stokes properties, which makes it suitable for use as a background-free biological imaging agent. As a result, R6G-conjugated AuNP is an effective theranostic agent that prevents the progression of cancer and MDR bacteria, along with contrasting abilities in medical imaging with minimal toxicity observed in in vitro and in vivo assays using zebrafish embryos. [ABSTRACT FROM AUTHOR]

We have prepared a pH and thermosensitive, fluorescent nanogel based on sodium alginate and itaconic acid as pH-sensitive moieties, diethylene glycol methyl ether acrylate as thermosensitive monomer and rhodamine B monomer as pH-sensitive fluorescent dye. The nanogel was characterized by Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1HNMR) spectroscopy. Also, scanning electron microscope (SEM) images were taken and indicated the relative uniform spherical particles with average diameter 250–300 nm. By enhancing the fluorescence emission at 576 nm, we confirmed that the pH sensitive property of the nanogel was more effective than that of the bare rhodamin B. Moreover, the nanogel including the diethylene glycol methyl ether acrylate exhibited changes in fluorescence intensity induced by temperature. By heating the nanogel dispersion to 40 °C, at acidic pH the rhodamine emission showed a considerable increase. This result indicated the occurrence of an efficient fluorescence resonance energy transfer (FRET) process between fluorescence dye and polymeric nanogel in collapsed state. Also, the thermo-responsibility of the nanogel was studied by dynamic light scattering (DLS) analysis which indicated the change in hydrodynamic diameter by changing the temperature. [ABSTRACT FROM AUTHOR]

We describe a π‐topological transformation‐based synthetic method for the preparation of a new type of near‐infrared (NIR)‐emissive rhodamine dye called Polymethine‐embedded Rhodamine Fluorophore (PeR Fluor). In contrast to conventional NIR‐emissive dyes that require tedious synthetic steps and/or a high cost, linear fully π‐conjugated PeR Fluor can be regioselectively prepared in one step by mixing different nucleophiles with ABPXs, a family of rhodamines with a cross‐conjugated structure. PeR Fluor exhibits bright NIR fluorescence emission and high photostability owing to the cooperative π‐electron system of rhodamines and polymethine scaffolds. Large bathochromic shifts of the absorption and fluorescence emission maxima can be achieved by modifying the N‐substituted group to obtain NIR‐absorbing/emitting PeR Fluor. We also demonstrate the stimulus‐responsive functionality of PeR Fluor through the addition of chemicals (acid/base), which shows switchable NIR and visible fluorescence response. Our π‐topological transformation‐based synthetic method is a promising approach to produce new functionalized rhodamine dyes. [ABSTRACT FROM AUTHOR]

Given the important role of carboxylesterase 2 (CES2) in the metabolism of various esters, it is of significance to develop a tool to determine endogenous CES2 activity in a rapid and highly selective manner. In this work, an "off-on" rhodamine-based fluorescent probe is reported as an effective tool for CES2 activity. Based on the substrate recognition preference of CES2 (large alcohol and small acyl groups), the probe with dimethyl carbamate as the recognition group performs well in terms of selectivity and sensitivity to CES2. The fluorescence switching control of the probe for CES2 was achieved by using the spirolactone structure of rhodamine. The probe shows the fast generation of a fluorescence signal at 634 nm upon hydrolysis of CES2 with excitation at 578 nm. The results showed a linear relationship between the fluorescence intensity at 634 nm and the CES2 activity from 0 to 4 μg/mL. The probe reacts rapidly with CES2, and the reaction is stable within 40 minutes. The probe is highly selective for CES2, with a detection limit as low as 0.303 μg/mL. In addition, the probe has currently been successfully utilized to evaluate CES2 activity in living cells. Hence, this probe is anticipated to be significant in identifying endogenous CES2 activity in intricate biological settings. [ABSTRACT FROM AUTHOR]

A fluorescent and colorimetric poly (acrylamide)-based copolymer probe P(AAm-co-RBNCH) has been designed via free radical polymerization of a commercial acrylamide monomer with a rhodamine-functionalized monomer RBNCH. Metal ion selectivity of RBNCH was investigated by fluorescence and colorimetric spectrophotometry. Upon addition of Fe3+, a visual color change from colorless to red and a large fluorescence enhancement were observed for the ring-opening of the rhodamine spirolactam mechanism. The monomer gives a sensitive method for quantitatively detecting Fe3+ in the linear range of 100–200 μM, with a limit of detection as low as 27 nM and exhibiting high selectivity for Fe3+ over 12 other metal ions. The hydrogel sensor was characterized by FTIR, and the effects of RBNCH amount on gel content and swelling properties were explored. According to the recipe of 1.0 mol% RBNCH to the total monomers, the fabricated hydrogel sensor displayed a good swelling property and reversibility performance and has potential for application in the imaging of Fe3+ level in industrial wastewater. [ABSTRACT FROM AUTHOR]

Disulfonated rhodamines are photostable and bright dyes widely used in life science and optical microscopy. However, di‐sulfonated dyes were considered cell impermeable and not applicable in living cells. We challenged this assumption with 5 most popular rhodamines (Rho) having two carboxylic acid residues, versatile sulfonation patterns and emitting green (AS488), yellow (Rho530), orange (Rho565) and red (Rho590 and STAR RED) light. The probes comprising one rhodamine entity and a HaloTagTM amine (O2) ligand (x) were prepared and applied for labeling of living, Vimentin‐Halo (VIM‐Halo) expressing U‐2 OS cells. Surprisingly, we observed specific and bright staining with simplest compounds Rho590‐x, Rho565‐x and Rho530‐x bearing two negative charges; they performed well also in stimulated emission depletion (STED) microscopy. Specific staining and red shifts in absorption and emission bands were observed with other probes having one negative charge; they were prepared by native chemical ligation and esterification. [ABSTRACT FROM AUTHOR]

The delivery of drugs through the skin barrier at a predetermined rate is the aim of transdermal drug delivery systems (TDDSs). However, so far, TDDS has not fully attained its potential as an alternative to hypodermic injections and oral delivery. In this study, we presented a proof of concept of a dual drug-loaded patch made of nanoparticles (NPs) and ultrafine fibers fabricated by using one equipment, i.e., the electrospinning apparatus. Such NP/fiber systems can be useful to release drugs locally through the skin and the tympanic membrane. Briefly, dexamethasone (DEX)-loaded poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) fiber meshes were decorated with rhodamine (RHO)-loaded poly(lactic-co-glycolic acid) (PLGA) NPs, with RHO representing as a second drug model. By properly tuning the working parameters of electrospinning, DEX-loaded PHBHV fibers (i.e., by electrospinning mode) and RHO-loaded PLGA NPs (i.e., by electrospray mode) were successfully prepared and straightforwardly assembled to form a TDDS patch, which was characterized via Fourier transform infrared spectroscopy and dynamometry. The patch was then tested in vitro using human dermal fibroblasts (HDFs). The incorporation of DEX significantly reduced the fiber mesh stiffness. In vitro tests showed that HDFs were viable for 8 days in contact with drug-loaded samples, and significant signs of cytotoxicity were not highlighted. Finally, thanks to a beaded structure of the fibers, a controlled release of DEX from the electrospun patch was obtained over 4 weeks, which may accomplish the therapeutic objective of a local, sustained and prolonged anti-inflammatory action of a TDDS, as is requested in chronic inflammatory conditions, and other pathological conditions, such as in sudden sensorineural hearing loss treatment. [ABSTRACT FROM AUTHOR]

The design and production of biodegradable and sustainable non-toxic materials for solar-energy harvesting and conversion is a significant challenge. Here, our goal was to report the preparation of novel protein/lipid hydrogels and demonstrate their utility in two orthogonal fundamental studies—light harvesting and white-light emission. Our hydrogels contained up to 90% water, while also being self-standing and injectable with a syringe. In one application, we loaded these hydrogels with suitable organic donor-acceptor dyes and demonstrated the energy-transfer cascade among four different dyes, with the most red-emitting dye as the energy destination. We hypothesized that the dyes were embedded in the protein/lipid phase away from the water pools as monomeric entities and that the excitation of any of the four dyes resulted in intense emission from the lowest-energy acceptor. In contrast to the energy-transfer cascade, we demonstrate the use of these gels to form a white-light-emitting hydrogel dye assembly, in which excitation migration is severely constrained. By restricting the dye-to-dye energy transfer, the blue, green, and red dyes emit at their respective wavelengths, thereby producing the composite white-light emission. The CIE color coordinates of the emission were 0.336 and 0.339—nearly pure white-light emission. Thus, two related studies with opposite requirements could be accommodated in the same hydrogel, which was made from edible ingredients by a simple method. These gels are biodegradable when released into the environment, sustainable, and may be of interest for energy applications. [ABSTRACT FROM AUTHOR]

A class of rhodamine‐based fluorescent sensors for the selective and sensitive detection of Pd2+ metal ions in aqueous media has been developed. A rhodamine‐based sensor PMS and a rhodamine‐BODIPY Förster resonance energy transfer (FRET)‐pair sensor PRS have been incorporated with a piperazine linker and an O−N−S−N podand ligand for specific recognition of Pd2+ ion. Both probes displayed colorimetric and fluorescent ratiometric changes when exposed to Pd2+, due to their spirolactam rings opening and restoring rhodamine conjugation. PRS is highly selective to Pd2+ over 22 other metal ions, showing a 0.6‐fold ratiometric difference at I600nm/I515nm. Additionally, the lactam ring in Pd2+ coordinated PRS‐Pd could be switched back to the closed form in the presence of various thiols, providing a "red‐green traffic light" detection mechanism between red and green emission. Furthermore, PRS showed excellent cell viability and was successfully employed to image Pd2+ and the PRS‐Pd complex ensemble could interchangeably detect biothiols including glutathione (GSH) in A549 human lung cancer cells. [ABSTRACT FROM AUTHOR]