Fluorescent Polymeric AND Logic Gate with Temperature and pH as Inputs

Harnessing split fluorescent proteins in modular protein logic for advanced whole-cell detection

Whole-cell biosensors have demonstrated promising capabilities in detecting target molecules. However, their limited selectivity and precision can be attributed to the broad substrate tolerance of natural proteins. In this study, we aim to enhance the performance of whole-cell biosensors by incorporating of logic AND gates. Specifically, we utilize the HrpR/S system, a widely employed hetero-regulation module from Pseudomonas syringae in synthetic biology, to construct an orthogonal AND gate in Escherichia coli. To accomplish this, we compare the HrpR/S system with self-associating split fluorescent proteins using the Spy Tag/Spy Catcher system. Our objective is to selectively activate a reporter gene in the presence of both IPTG and Hg(II) ions. Through systematic genetic engineering and evaluation of various biological parts under diverse working conditions, our research demonstrates the utility of self-associating split fluorescent proteins in developing high-performance whole-cell biosensors. This approach offers advantages such as engineering simplicity, reduced basal activity, and improved selectivity. Furthermore, the comparison with the HrpR/S system serves as a valuable control model, providing insights into the relative advantages and limitations of each approach. These findings present a systematic and adaptable strategy to overcome the substrate tolerance challenge faced by whole-cell biosensors.

Quinolinium-Based Fluorescent Probes for Dynamic pH Monitoring in Aqueous Media at High pH Using Fluorescence Lifetime Imaging

Spatiotemporal pH imaging using fluorescence lifetime imaging microscopy (FLIM) is an excellent technique for investigating dynamic (electro)chemical processes. However, probes that are responsive at high pH values are not available. Here, we describe the development and application of dedicated pH probes based on the 1-methyl-7-amino-quinolinium fluorophore. The high fluorescence lifetime and quantum yield, the high (photo)stability, and the inherent water solubility make the quinolinium fluorophore well suited for the development of FLIM probes. Due to the flexible fluorophore-spacer-receptor architecture, probe lifetimes are tunable in the pH range between 5.5 and 11. An additional fluorescence lifetime response, at tunable pH values between 11 and 13, is achieved by deprotonation of the aromatic amine at the quinolinium core. Probe lifetimes are hardly affected by temperature and the presence of most inorganic ions, thus making FLIM imaging highly reliable and convenient. At 0.1 mM probe concentrations, imaging at rates of 3 images per second, at a resolution of 4 μm, while measuring pH values up to 12 is achieved. This enables the pH imaging of dynamic electrochemical processes involving chemical reactions and mass transport.

Visible light responsive photoacids for subcellular pH and temperature correlated fluorescence sensing

Liao's photoacids (PAs) are a well-known type of visible light-responsive photoswitches. Here, taking advantage of the temperature-dependent thermal relaxation from the ring-closed to the ring-opened forms, PAs are proposed for the first time as a fluorescent temperature sensor in cells. The logarithmic lifetime (ln τ) of the ring-closed spiro-form exhibited an excellent linear response to the reciprocal of the temperature. In addition, the fluorescent ring-opened PAs were able to highlight lysosomes and responded to lysosomal pH changes. These properties made the PAs promising fluorescent probes in the sensing of subcellular pH and temperature.

High-contrast reversible multiple color-tunable solid luminescent ionic polymers for dynamic multilevel anti-counterfeiting

Dynamic color-tunable luminescent materials, which possess huge potential applications in advanced multilevel luminescence anti-counterfeiting, are of considerable interest. However, it remains challenging to develop simple high-contrast reversible multiple (triple or more than triple) color-tunable high-efficiency solid luminescent materials with low cost, facile synthesis, and good processability. Herein, by simply grafting charged multi-color AIEgen-based chromophores into polymers, a series of high-efficiency multiple color-tunable luminescent single ionic polymers are constructed through tuning feed ratios, counter anions and reaction solvents. Remarkably, some ionic polymers can not only achieve rare high-contrast reversible multiple color-tunable emission in solid states in response to different solvent stimuli, but also could realize excitation-dependent color-tunable emission. To the best of our knowledge, such charming multiple (triple or more than triple) color-tunable solid polymers responding to multiple external stimuli are still rare. Based on comparative studies of emission spectra, excitation spectra and fluorescence lifetimes before and after swelling, it could be inferred that solvent stimuli could induce microstructure changes of these ionic polymers and then change the aggregated-states of their corresponding AIE-active emission centers. Moreover, the different solvent stimuli could induce to produce different degrees of microstructure changes, resulting in their unique multiple color-tunable emission. More significantly, these smart color-tunable ionic polymers show great promise for applications in dynamic multilevel (three-level or even more than three-level) anti-counterfeiting.

Rational construction of a fluorescent sensor for simultaneous detection and imaging of hypochlorous acid and peroxynitrite in living cells, tissues and inflammatory rat models

Modern medical research indicates that hypochlorous acid (HClO) and peroxynitrite (ONOO^-) are important biomarkers of oxidative stress. However, the up- or down-regulation of HClO or ONOO^- has been closely associated with the occurrence and development of various diseases. In order to investigate the intrinsic entanglement relationship between HClO and ONOO^- and their relationship with the occurrence and development of inflammation, it is very valuable to develop fluorescent sensors that are capable of displaying different signals towards HClO, ONOO^- and HClO/ONOO^-. In this work, we rationally design and construct a novel robust small organic molecule fluorescent sensor (RhNp-ClO-ONOO) towards ONOO^-, HClO and HClO/ONOO^- with green, red, and green-red three different fluorescent signal outputs, respectively. RhNp-ClO-ONOO has fast responsive time for HClO (∼60 s) and ONOO^- (∼20 s). Also it has markedly low detection limits for HClO (∼25.3 nM) and ONOO^- (12.4 nM) respectively. In addition, RhNp-ClO-ONOO could be further shown to detect endogenous HClO/ONOO^- in living cells, inflammatory tissues and rat model successfully. Therefore, this novel fluorescent sensor with double responsive moiety can offer a powerful tool for studying the role of HClO and ONOO^- and the occurrence and development of inflammatory diseases.

A Lanthanide Upconversion Nanothermometer for Precise Temperature Mapping on Immune Cell Membrane

Cell temperature monitoring is of great importance to uncover temperature-dependent intracellular events and regulate cellular functions. However, it remains a great challenge to precisely probe the localized temperature status in living cells. Herein, we report a strategy for in situ temperature mapping on an immune cell membrane for the first time, which was achieved by using the lanthanide-doped upconversion nanoparticles. The nanothermometer was designed to label the cell membrane by combining metabolic labeling and click chemistry and can leverage ratiometric upconversion luminescence signals to in situ sensitively monitor temperature variation (1.4% K^-1). Moreover, a purpose-built upconversion hyperspectral microscope was utilized to synchronously map temperature changes on T cell membrane and visualize intracellular Ca²⁺ influx. This strategy was able to identify a suitable temperature status for facilitating thermally stimulated calcium influx in T cells, thus enabling high-efficiency activation of immune cells. Such findings might advance understandings on thermally dependent biological processes and their regulation methodology.

Scalable Production of Self-Toughening Plant Oil-Based Polyurethane Elastomers with Multistimuli-Responsive Functionalities

Plant oils are becoming of high industrial importance due to the persisting challenges befalling with the utilization of fossil fuels. Thus, developing methodologies to produce multifunctional materials by taking advantage of the unique structure of plant oil is highly desired. In this study, castor oil served as a cross-linker and soft segments, by incorporating scalable rhodamine 6G derivatives, to systematically synthesize a series of smart polymers that possess self-toughening and multistimuli-responsive capabilities. The polyurethane elastomers showed 10 times and 60 times increases in tensile strength and toughness, respectively, in comparison with the unmodified polyurethane due to the existence of large amounts of hydrogen bonding, dynamic C-N spiro bonds, rigid benzene ring, and high cross-link densities. The novel polyurethane elastomers exhibited excellent reversible multichromic behaviors in response to light, pH, and mechanics. Notably, the resulting polyurethane elastomers exhibited ultrasensitive sustained photochromism with tunable white emission and rapid reversibility. This study provides a simple and effective strategy to utilize plant oil for multifunctional material preparation and paves the way to open access for application of plant oil-based products in a variety of industry applications, such as sensors, self-fitting tissue scaffolds, and switchable devices.

Molecular logic operations from complex coacervation with aggregation-induced emission characteristics

Leveraging complex coacervation of a polycation and a bivalent anion with aggregation-induced emission characteristics, we accomplish eight basic logic operations with environmental stimuli as inputs, producing Boolean-like fluorescence intensity or turbidity 'outputs' with contrast higher than one order of magnitude. Storage of information of a fluorescent pattern and thermo-sensor applications are also demonstrated.

Double hydrophilic copolymers - synthetic approaches, architectural variety, and current application fields

Solubility and functionality of polymeric materials are essential properties determining their role in any application. In that regard, double hydrophilic copolymers (DHC) are typically constructed from two chemically dissimilar but water-soluble building blocks. During the past decades, these materials have been intensely developed and utilised as, e.g., matrices for the design of multifunctional hybrid materials, in drug carriers and gene delivery, as nanoreactors, or as sensors. This is predominantly due to almost unlimited possibilities to precisely tune DHC composition and topology, their solution behavior, e.g., stimuli-response, and potential interactions with small molecules, ions and (nanoparticle) surfaces. In this contribution we want to highlight that this class of polymers has experienced tremendous progress regarding synthesis, architectural variety, and the possibility to combine response to different stimuli within one material. Especially the implementation of DHCs as versatile building blocks in hybrid materials expanded the range of water-based applications during the last two decades, which now includes also photocatalysis, sensing, and 3D inkjet printing of hydrogels, definitely going beyond already well-established utilisation in biomedicine or as templates.

Harnessing Thorpe-Ingold Dialkylation to Access High-Hill-Percentage pH Probes

Sensitivity is an important parameter for a molecular probe. Hill-type pH probes exhibit improved detection sensitivity compared to the traditional pH probes following the Henderson-Hasselbalch equation. Exploiting positive cooperativity, we recently devised a novel molecular scaffold (PHX) to offer such an unconventional Hill-type pH titration profile. We previously confirmed that PHX is not a pure Hill-type probe yet. Only 64% of its absorbance/fluorescence turn-on is the result of a Hill-type pathway. The remaining 36% is from an undesired Henderson-Hasselbalch-type pathway (HH pathway). In this work, the Thorpe-Ingold dialkylation was harnessed to further suppress the percent contribution of the HH pathway down to 16%. We also propose that PHX is a viable molecular model for assessing the efficacy of the steric compressing effect induced by different Thorpe-Ingold dialkylations.

Amphiphilic Asymmetric Diblock Copolymer with pH-Responsive Fluorescent Properties

Stimuli-responsive polymers with changeable fluorescent properties have numerous applications in sensing, bioimaging, and detection. Here we describe the facile synthesis of a pH-responsive amphiphilic asymmetric diblock copolymer of acrylic acid and butyl acrylate that incorporates a polarity-sensitive fluorophore. The asymmetric structure enhances the stimuli-responsive behavior: as the environmental pH decreases, the fluorescent intensity of the asymmetric diblock copolymer gradually increases, whereas its symmetric block counterpart shows limited and stepwise change. Besides, this remarkable difference was demonstrated to be concentration-independent, as similar emission behavior was found for both polymers at lower concentrations. These results indicate that the fluorescence properties of the copolymer can be adjusted by rationally designing the copolymer structure. This work provides a novel and general strategy for the design and synthesis of polymeric materials with encapsulated structures showing stimuli-responsive fluorescent properties to be applied as fluorescent probes with a smoothly varying response curve rather than the simple on-off switch that is typical of block copolymer systems.

Upper and Apparent Lower Critical Solution Temperature Branches in the Phase Diagram of Polymer:Small Molecule Semiconducting Systems

Solution-processable semiconducting materials are complex materials with a wide range of applications. Despite their extensive study and utility, their molecular interactions as manifested, for example, in phase behavior are poorly understood. Here, we aim to understand the phase behavior of conjugated systems by determining phase diagrams spanning extensive temperature ranges for various combinations of the highly disordered semiconducting polymer (PTB7-Th) with crystallizable (IT-M and PC₆₁BM) and noncrystallizable (di-PDI) small molecule acceptors (SMAs), with polystyrene as an amorphous control, a nonsemiconducting commodity polymer. We discover that the apparent binodal of the studied blends frequently consists of an upper critical solution temperature (UCST) and lower critical solution temperature (LCST) branch, exhibiting a sharp kink where the branches join. Our work suggests that phase diagrams might be a probe in combination with sophisticated models to understand the complexity of semiconducting materials, including microstructure and molecular interactions.

Colloidal Self-Assembly Approaches to Smart Nanostructured Materials

Colloidal self-assembly refers to a solution-processed assembly of nanometer-/micrometer-sized, well-dispersed particles into secondary structures, whose collective properties are controlled by not only nanoparticle property but also the superstructure symmetry, orientation, phase, and dimension. This combination of characteristics makes colloidal superstructures highly susceptible to remote stimuli or local environmental changes, representing a prominent platform for developing stimuli-responsive materials and smart devices. Chemists are achieving even more delicate control over their active responses to various practical stimuli, setting the stage ready for fully exploiting the potential of this unique set of materials. This review addresses the assembly of colloids into stimuli-responsive or smart nanostructured materials. We first delineate the colloidal self-assembly driven by forces of different length scales. A set of concepts and equations are outlined for controlling the colloidal crystal growth, appreciating the importance of particle connectivity in creating responsive superstructures. We then present working mechanisms and practical strategies for engineering smart colloidal assemblies. The concepts underpinning separation and connectivity control are systematically introduced, allowing active tuning and precise prediction of the colloidal crystal properties in response to external stimuli. Various exciting applications of these unique materials are summarized with a specific focus on the structure-property correlation in smart materials and functional devices. We conclude this review with a summary of existing challenges in colloidal self-assembly of smart materials and provide a perspective on their further advances to the next generation.

Fluorescent Molecular Logic Gates Driven by Temperature and by Protons in Solution and on Solid

Temperature-driven fluorescent NOT logic is demonstrated by exploiting predissociation in a 1,3,5-trisubstituted Δ² -pyrazoline on its own and when grafted onto silica microparticles. Related Δ² -pyrazolines become proton-driven YES and NOT logic gates on the basis of fluorescent photoinduced electron transfer (PET) switches. Additional PASS 1 and YES+PASS 1 logic gates on silica are also demonstrated within the same family. Beside these small-molecule systems, a polymeric molecular thermometer based on a benzofurazan-derivatized N-isopropylacrylamide copolymer is attached to silica to produce temperature-driven fluorescent YES logic.

Infochemistry and the Future of Chemical Information Processing

Nowadays, information processing is based on semiconductor (e.g., silicon) devices. Unfortunately, the performance of such devices has natural limitations owing to the physics of semiconductors. Therefore, the problem of finding new strategies for storing and processing an ever-increasing amount of diverse data is very urgent. To solve this problem, scientists have found inspiration in nature, because living organisms have developed uniquely productive and efficient mechanisms for processing and storing information. We address several biological aspects of information and artificial models mimicking corresponding bioprocesses. For instance, we review the formation of synchronization patterns and the emergence of order out of chaos in model chemical systems. We also consider molecular logic and ion fluxes as information carriers. Finally, we consider recent progress in infochemistry, a new direction at the interface of chemistry, biology, and computer science, considering unconventional methods of information processing.

Performing calculus: Asymmetric adaptive stimuli-responsive material for derivative control

Materials (e.g., brick or wood) are generally perceived as unintelligent. Even the highly researched "smart" materials are only capable of extremely primitive analytical functions (e.g., simple logical operations). Here, a material is shown to have the ability to perform (i.e., without a computer), an advanced mathematical operation in calculus: the temporal derivative. It consists of a stimuli-responsive material coated asymmetrically with an adaptive impermeable layer. Its ability to analyze the derivative is shown by experiments, numerical modeling, and theory (i.e., scaling between derivative and response). This class of freestanding stimuli-responsive materials is demonstrated to serve effectively as a derivative controller for controlled delivery and self-regulation. Its fast response realizes the same designed functionality and efficiency as complex industrial derivative controllers widely used in manufacturing. These results illustrate the possibility to associate specifically designed materials directly with higher concepts of mathematics for the development of "intelligent" material-based systems.

Triphenyl-imidazole based reversible coloro/fluorimetric sensing and electrochemical removal of Cu2+ ions using capacitive deionization and molecular logic gates

A simple hydroxyl-substituted triphenyl-imidazole based receptor (HTPI) which selectively detects Cu²⁺ ion by colorimetric and fluorimetric methods was developed. HTPI detects the Cu²⁺ ions with the absorption enhancement and fluorescence quenching by the possible ligand to metal charge transfer (LMCT) and the chelation-enhanced quenching (CHEQ) approaches, respectively. HTPI showed high selectivity and sensitivity for Cu²⁺ ions detection over other interfering and competing metal ions. Interestingly, HTPI detects Cu²⁺ ion (LOD) at nanomolar concentrations (19 × 10^-9 M (UV-vis) & 27 × 10^-9 M (fluorescence), respectively), which is lower than the permissible level of Cu²⁺ ion reported by World Health Organization (WHO). Furthermore, HTPI was applied to the molecular logic gate function by using chemical inputs, and Cu²⁺ ion was potentially removed (95%) via Capacitive Deionization technique.

Carbon Dots-Based Logic Gates

Carbon dots (CDs)-based logic gates are smart nanoprobes that can respond to various analytes such as metal cations, anions, amino acids, pesticides, antioxidants, etc. Most of these logic gates are based on fluorescence techniques because they are inexpensive, give an instant response, and highly sensitive. Computations based on molecular logic can lead to advancement in modern science. This review focuses on different logic functions based on the sensing abilities of CDs and their synthesis. We also discuss the sensing mechanism of these logic gates and bring different types of possible logic operations. This review envisions that CDs-based logic gates have a promising future in computing nanodevices. In addition, we cover the advancement in CDs-based logic gates with the focus of understanding the fundamentals of how CDs have the potential for performing various logic functions depending upon their different categories.

Novel PET-pperated rosamine pH-sensor dyes with substitution pattern-tunable pKa values and temperature sensitivity

We present the synthesis and characterization of a family of regioisomerically pure pH-sensitive rosamine fluorophores consisting of xanthene fluorophore cores and differently substituted phenol moieties.

A fluorescent polymeric INHIBIT logic gate based on the natural product quinidine

The natural product quinidine was polymerised with acrylamide and demonstrated as a H⁺-enabled, Cl⁻-disabled INHIBIT logic gate in water.

Temperature Sensing in the Short-Wave Infrared Spectral Region Using Core-Shell NaGdF4:Yb3+, Ho3+, Er3+@NaYF4 Nanothermometers

The short-wave infrared region (SWIR) is promising for deep-tissue visualization and temperature sensing due to higher penetration depth and reduced scattering of radiation. However, the strong quenching of luminescence in biological media and low thermal sensitivity of nanothermometers in this region are major drawbacks that limit their practical application. Nanoparticles doped with rare-earth ions are widely used as thermal sensors operating in the SWIR region through the luminescence intensity ratio (LIR) approach. In this study, the effect of the shell on the sensitivity of temperature determination using NaGdF₄ nanoparticles doped with rare-earth ions (REI) Yb³⁺, Ho³⁺, and Er³⁺ coated with an inert NaYF₄ shell was investigated. We found that coating the nanoparticles with a shell significantly increases the intensity of luminescence in the SWIR range, prevents water from quenching luminescence, and decreases the temperature of laser-induced heating. Thermometry in the SWIR spectral region was demonstrated using synthesized nanoparticles in dry powder and in water. The core-shell nanoparticles obtained had intense luminescence and made it possible to determine temperatures in the range of 20–40 °C. The relative thermal sensitivity of core-shell NPs was 0.68% °C⁻¹ in water and 4.2% °C⁻¹ in dry powder.

Fluorescence for biological logic gates

Biological logic gates are smart probes able to respond to biological conditions in behaviors similar to computer logic gates, and they pose a promising challenge for modern medicine. Researchers are creating many kinds of smart nanostructures that can respond to various biological parameters such as pH, ion presence, and enzyme activity. Each of these conditions alone might be interesting in a biological sense, but their interactions are what define specific disease conditions. Researchers over the past few decades have developed a plethora of stimuli-responsive nanodevices, from activatable fluorescent probes to DNA origami nanomachines, many explicitly defining logic operations. Whereas many smart configurations have been explored, in this review we focus on logic operations actuated through fluorescent signals. We discuss the applicability of fluorescence as a means of logic gate implementation, and consider the use of both fluorescence intensity as well as fluorescence lifetime.

Novel excited-state nanothermometry combining the red-shift of charge-transfer bands and a thermal coupling effect

Unprecedented excited-state nanothermometry with high sensitivity and low temperature uncertainty is proposed by combining the red-shift of V–O charge-transfer bands and a thermal coupling effect.

Fluorescent molecular logic gates based on photoinduced electron transfer (PET) driven by a combination of atomic and biomolecular inputs

A meeting point for entities from chemistry, enzymology and computer science.

Doping Dopamine in Carbon Nanoparticles: A New Multifunctional Logic-Based Decision-Making Molecule

A dopamine-functionalized carbon nanoparticle (CNP)-based platform is designed to reversibly control the optical signal, leading to a multifunctional logic system regulated by pH and light. pH-regulated unique reversible transformation of oxidized and reduced forms of a neurotransmitter, dopamine, conjugated with CNPs plays a decisive role in capturing the final output of the logic function. Inspired by this phenomenon, herein, we report the use of dopamine-docked CNPs to construct different molecular logic gates with an intention to develop the next-generation molecular logic gates. We could successfully construct two basic molecular logic gates, namely, YES and NOT, using one input; two modular logic gates; an IMPLICATION logic gate using two inputs; and finally a combination of OR and AND gates using three inputs. The optical response of the synthesized NP conjugate provides a fluorescence-based "Erase-Read-Write-Read" function. The proposed phenomenon may open a new concept of biochemical logic gates with fluorescence output for neuronal imaging.

A Personal Journey across Fluorescent Sensing and Logic Associated with Polymers of Various Kinds

Our experiences concerning fluorescent molecular sensing and logic devices and their intersections with polymer science are the foci of this brief review. Proton-, metal ion- and polarity-responsive cases of these devices are placed in polymeric micro- or nano-environments, some of which involve phase separation. This leads to mapping of chemical species on the nanoscale. These devices also take advantage of thermal properties of some polymers in water in order to reincarnate themselves as thermometers. When the phase separation leads to particles, the latter can be labelled with identification tags based on molecular logic. Such particles also give rise to reusable sensors, although molecular-scale resolution is sacrificed in the process. Polymeric nano-environments also help to organize rather complex molecular logic systems from their simple components. Overall, our little experiences suggest that researchers in sensing and logic would benefit if they assimilate polymer concepts.

Responsive Polymers as Smart Nanomaterials Enable Diverse Applications

Responsive polymers undergo reversible or irreversible physical or chemical modifications in response to a change in environment or stimulus, e.g., temperature, pH, light, and magnetic or electric fields. Polymeric nanoparticles (NPs), which constitute a diverse set of morphologies, including micelles, vesicles, and core-shell geometries, have been successfully prepared from responsive polymers and have shown great promise in applications ranging from drug delivery to catalysis. In this review, we summarize pH, thermo-, photo-, and enzymatic responsiveness for a selection of polymers. We then discuss the formation of NPs made from responsive polymers. Finally, we highlight how NPs and other nanomaterials are enabling a wide range of smart applications with improved efficiency, as well as improved sustainability and recyclability of polymeric systems.

Understanding the effect of monomer structure of oligoethylene glycol acrylate copolymers on their thermoresponsive behavior for the development of polymeric sensors

Oligoethylene glycol acrylate (OEGA) polymers are a class of thermoresponsive polymers. Three new OEGA monomer combinations were investigated, which revealed three different types of thermoresponsive behavior as a function of copolymer composition.

Nanoscopic hydrophilic/hydrophilic phase-separation well below the LCST of polyphosphoesters

The complex phase separation process of thermoresponsive polyphosphoesters (PPEs) with an identical side-group structure but different copolymer compositions is characterized by electron paramagnetic resonance (EPR) spectroscopy.

A turn-on fluorescent probe with a dansyl fluorophore for hydrogen sulfide sensing

Hydrogen sulfide (H₂S) is a biologically relevant molecule that has been newly identified as a gasotransmitter and is also a toxic gaseous pollutant. In this study, we report on a metal complex fluorescent probe to achieve the sensitive detection of H₂S in a fluorescent “turn-on” mode. The probe bears a dansyl fluorophore with multidentate ligands for coordination with copper ions. The fluorescent “turn-on” mode is facilitated by the strong bonding between H₂S and the Cu(ii) ions to form insoluble copper sulfide, which leads to the release of a strongly fluorescent product. The H₂S limit of detection (LOD) for the proposed probe is estimated to be 11 nM in the aqueous solution, and the utilization of the probe is demonstrated for detecting H₂S in actual lake and mineral water samples with good reproducibility. Furthermore, we designed detector vials and presented their successful application for the visual detection of gaseous H₂S.

H₂S turn on the fluorescence of DNS–Cu complex probe.

A2B corroles: Fluorescence signaling systems for sensing fluoride ions

Four free base corroles, 1-4, A₂B, (where A = nitrophenyl, and B = pentafluorophenyl, 2, 6-difluoro, 3, 4, 5-trifluoro and 4-carboxymethylphenyl group) have been synthesized, characterized and demonstrated as excellent chemosensor for the detection of fluoride ions selectively in toluene solution. The reported corroles shows highest quantum yield in free base form of porphyrinoid systems so far. All these corrole, 1-4, have the excellent ability to sense fluoride ion. Cumulative effect of static and dynamic factors is responsible for the quenching of fluorescence which indicates the detection of fluoride ion in solution.

Amphiphilic Carbazole-Containing Compounds with Lower Critical Solution Temperature Behavior for Supramolecular Self-Assembly and Solution-Processable Resistive Memories

The self-organization and resistive memory performances of a series of newly synthesized water-soluble amphiphilic carbazole derivatives have been explored. Temperature-dependent UV/Vis absorption spectroscopy has been conducted to study the isodesmic self-assembly mechanism of the carbazole-containing compounds. This class of compounds also exhibits interesting lower critical solution temperature properties, which are sensitive to concentration and ionic additives. One of the compounds has been solution-processed and utilized as an active material in the engineering of resistive memory devices, exhibiting a switching voltage of about 3.9 V, a constant ON/OFF current ratio of 10⁶ , and a long retention time of 10⁴  s. The present work demonstrates the versatile potential applications of water-soluble amphiphilic carbazole-containing compounds in supramolecular chemistry and resistive memory devices.

A photo-switchable and thermal-enhanced fluorescent hydrogel prepared from N-isopropylacrylamide with water-soluble spiropyran derivative

Herein, a photo-switchable and thermal-enhanced fluorescent hydrogel has been fabricated from N-isopropylacrylamide (NIPAAm) with a mixture of water-soluble acryloyl-α-cyclodextrin/acryloyl-α-cyclodextrin-spiropyran (acryloyl-α-CD/ acryloyl-α-CD-SP) as cross-linkers. The physical properties, photochromic properties, and fluorescent behavior of the hydrogel were characterized. The fluorescence emission of the hydrogel can be reversibly switched 'on/off' by UV/visible light irradiation, and meanwhile the fluorescence intensity can be enhanced by increasing the temperature above the volume phase transition temperature (VPTT) of the hydrogel. The hydrogel also shows spatiotemporal fluorescent behavior, excellent cytocompatibility, and fatigue resistance in photochromic and photo-switchable fluorescent behaviors.

Highly Sensitive Hill-Type Small-Molecule pH Probe That Recognizes the Reversed pH Gradient of Cancer Cells

A hallmark of cancer cells is a reversed transmembrane pH gradient, which could be exploited for robust and convenient intraoperative histopathological analysis. However, pathologically relevant pH changes are not significant enough for sensitive detection by conventional Henderson-Hasselbalch-type pH probes, exhibiting an acid-base transition width of 2 pH units. This challenge could potentially be addressed by a pH probe with a reduced acid-base transition width (i.e., Hill-type probe), appropriate p K_a, and membrane permeability. Yet, a guideline to allow rational design of such small-molecule Hill-type pH probes is still lacking. We have devised a novel molecular mechanism, enabled sequential protonation with high positive homotropic cooperativity, and synthesized small-molecule pH probes (PHX1-3) with acid-base transition ranges of ca. 1 pH unit. Notably, PHX2 has a p K_a of 6.9, matching the extracellular pH of cancer cells. Also, PHX2 is readily permeable to cell membrane and allowed direct mapping of both intra- and extracellular pH, hence the transmembrane pH gradient. PHX2 was successfully used for rapid and high-contrast distinction of fresh unprocessed biopsies of cancer cells from normal cells and therefore has broad potentials for intraoperative analysis of cancer surgery.