Constructing Ultra-Strong SERS Tags in the Cellular Raman-Silent Region by Orthogonal Array Testing Strategy.

Surface-enhanced Raman spectroscopy (SERS) tags have the advantages of unique fingerprint vibration spectrum, ultranarrow spectral line widths, and weak photobleaching effect, showing great potential for bioimaging. However, SERS imaging is still hindered for further application due to its weak spontaneous Raman scattering, biomolecular signal interference, and long acquisition times. Here, we develop a novel SERS tag of the core (Au)-shell (N-doped graphene) structure (Au@NGs) with ultrastrong and stable Raman signal (2180 cm-1) in the cellular Raman-silent region (1800-2800 cm-1) through base-promoted oxidative decarboxylation of amino acids. Exploring the factors (metal salts, amino acids, catalysts, temperature, etc.) to obtain Au@NGs with the strongest Raman signal commonly requires more than 100,000 separate experiments, while that using an orthogonal array testing strategy is reduced to 56. The existence of deep charge transfer between the Au surface and C≡N-graphene is proved by theoretical calculations, which means the ultrastrong signal of Au@NGs is the joint effect of electromagnetic and chemical enhancement. The Au@NGs have a detection sensitivity down to a single-nanoparticle level, and high-speed and high-resolution cellular imaging (4453 pixels) is obtained within 10 s by global Raman imaging. The combination of Au@NGs-based tags with ultrastrong intrinsic Raman imaging capability and global imaging technology holds great promise for high-speed Raman imaging.

Visible Light-Responsive Crystalline B←N Host Adducts with Solvent-Induced Allosteric Effect for Guest Release.

Photo-responsive organic crystals, capable of converting light energy into chemical energy to initiate conformational transitions, present an emerging strategy for developing lightweight and versatile smart materials. However, visible light-triggered tailored guests capture and release behaviors in all-organic solids are rarely reported. Here, we introduce a photoreactive crystalline boron-nitrogen (B←N) host adduct with the ability to undergo [2+2] photocycloaddition upon 447 nm light exposure. This process facilitates single-crystal-to-single-crystal (SCSC) photodimerization in the mother liquor, maintaining the original B←N host structure. Weakened intermolecular interactions within the photodimer host contribute to fast guest release in air under irradiation. Furthermore, the dynamic B←N bonds enable reversible transformations between organic host adducts and adduct cocrystals under the solvent-induced allosteric effect. As a result, four B←N host adduct crystals containing individual alkane guest are easily obtained and exhibited the ability of photo-controlled alkane release. Therefore, the integration of photo reactivity and structural transformation within B←N host adduct enables customized capture and release of guest molecules.

Stable Organic Radicals Participation in Charge Transfer: A New Strategy toward Molecular Functional Materials.

Charge-transfer (CT) engineering with inter-/intramolecular CT interactions by simple compositions has emerged as a universal and efficient way to construct organic functional materials. Stable organic radicals with unique physicochemical properties that cannot be realized in closed-shell molecules, have been widely demonstrated to be ideal building blocks to construct versatile organic CT materials. This concept article provides a brief overview of the advances in the design, structure and property of stable organic radicals-based CT molecular functional materials, and the strategy for the generation of these materials is also highlighted. First, radicals are introduced as open-shell donors or acceptors, with a focus on their importance and uniqueness in improving electrical, magnetic and optical properties of CT functional materials. Additionally, CT interactions in stable radical dimers and trimers are further discussed systematically. Finally, the challenges are summarized and perspectives for future development of stable organic radicals-based CT functional materials are provided.

Heat Confinement Aerogel Enables Supramagnetothermal Effect for Triggering Nitric Oxide Generation.

Reducing heat dissipation plays an indispensable role in boosting the magnetothermal effect but has received scant attention. Herein, a magnetothermal aerogel (MA) combining an efficient magnetothermal convertor for heat generation and a highly porous aerogel for reducing heat dissipation is developed. Such a heat confinement MA shows a large thermal resistance and high infrared absorption that can effectively confine the heat by regulating interior thermal conduction and radiation, exhibiting a supramagnetothermal effect. In addition, a waterproof beeswax coated MA achieves negligible heat loss and a supramagnetothermal effect even in high-thermal-diffusion aqueous media. As a proof of concept, a synthesized heat-triggered nitric oxide (NO) precursor is integrated into an MA, and the rapid NO generation (∼22 µM/min) resulting in an antibacterial effect further verifies the supramagnetothermal effect of the MA. This work provides an efficient strategy to promote the magnetothermal effect and offers inspiration for building a heat-triggering system.

Charge-Transfer Cocrystal via a Persistent Radical Cation Acceptor for Efficient Solar-Thermal Conversion.

Designing organic charge-transfer (CT) cocrystals for efficient solar-thermal conversion is a long-sought goal but remains challenging. Here we construct a unique CT cocrystal by using a persistent 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+. ) as the electron acceptor. The strong persistency and electron affinity of ABTS+. endow a high degree of electron delocalization between ABTS+. and the 3,3',5,5'-tetramethylbenzidine donor. Together with the intrinsic long-wavelength absorption of ABTS+. , the synthesized cocrystal can effectively capture the full solar spectrum and show distinguished photothermal efficiency. Such a cocrystal is further used for solar-driven interfacial evaporation, and a high evaporation rate of 1.407 kg m-2 h-1 and a remarkable solar-to-vapor efficiency of 97.0 % have been achieved upon 1 sun irradiation. This work indicates the enormous prospects for charge transfer-based functional materials through rational radical cation engineering.

A crown ether embedded responsive π-gelator for transition from a one-component gel to a two-component gel.

A novel fluorescent π-gelator, incorporating a crown ether with host-guest recognition capability and a photoactive cyanostilbene unit, was designed. This unique structure enables the successful transition from a one-component gel to a two-component gel and exhibits gel-sol transition behaviors under heat, ions, and light stimuli.

Highly Active CoRh Graphitic Nanozyme for Colorimetric Sensing in Real Samples.

Rh-based nanozymes show high catalytic efficiency, specific surface area, good stability, and unique physicochemical properties, while magnetic nanozymes facilitate the magnetic separation of detection samples under an external magnetic field for improved sensitivity. However, magnetic Rh nanozymes, especially those with excellent stability, have not been reported. Herein, we apply the chemical vapor deposition (CVD) method to prepare a CoRh graphitic nanozyme (termed as CoRh@G nanozyme), which structurally consists of CoRh nanoalloy encapsulated by a few layers of graphene for sensitive colorimetric sensing applications. The proposed CoRh@G nanozyme has superior peroxidase (POD)-like activity, and it shows higher affinity of the CoRh@G nanozyme than horseradish peroxidase (HRP) toward 3,3',5,5'-tetramethylbenzydine (TMB) oxidation. In addition, the CoRh@G nanozyme shows high durability and superior recyclability owing to its protective graphitic shell. The outstanding merits of the CoRh@G nanozyme allow its use for quantitative colorimetric detection of dopamine (DA) and ascorbic acid (AA), showing high sensitivity and good selectivity. Moreover, it shows satisfactory performance for AA detection in commercial beverages and energy drinks. The proposed CoRh@G nanozyme-based colorimetric sensing platform shows great promise in point-of-care (POC) visual monitoring.

Dual Charge Transfer Generated from Stable Mixed-Valence Radical Crystals for Boosting Solar-to-Thermal Conversion.

Realizing dual charge transfer (CT) based on stable organic radicals in one system is a long-sought goal, however, remains challenging. In this work, a stable mixed-valence radical crystal is designed via a surfactant-assisted method, namely TTF-(TTF+• )2 -RC (where TTF = tetrathiafulvalene), containing dual CT interactions. The solubilization of surfactants enables successful co-crystallization of mixed-valence TTF molecules with different polarity in aqueous solutions. Short intermolecular distances between adjacent TTF moieties within TTF-(TTF+• )2 -RC facilitate both inter-valence CT (IVCT) between neutral TTF and TTF+• , and inter-radical CT (IRCT) between two TTF+• in radical π-dimer, which are confirmed by single-crystal X-ray diffraction, solid-state absorption, electron spin resonance measurements, and DFT calculations. Moreover, TTF-(TTF+• )2 -RC reveals an open-shell singlet diradical ground state with the antiferromagnetic coupling of 2J = -657 cm-1 and an unprecedented temperature-dependent magnetic property, manifesting the main monoradical characters of IVCT at 113-203 K while the spin-spin interactions in radical dimers of IRCT are predominant at 263-353 K. Notably, dual CT characters endow TTF-(TTF+• )2 -RC with strong light absorption over the full solar spectrum and outstanding stability. As a result, TTF-(TTF+• )2 -RC exhibits significantly enhanced photothermal property, an increase of 46.6 °C within 180 s upon one-sun illumination.

Highly efficient carbon supported Co-Ir nanozyme for the determination of total antioxidant capacity in foods.

Nanozyme-based colorimetric assays have aroused extensive attention in biosensing due to quick response, low cost and simplicity. However, their practical applications are limited by the unsatisfactory stability and catalytic activity of nanozymes in complex detection environments. Herein, using the one-pot chemical vapor deposition method, we successfully prepare a highly efficient and stable carbon supported Co-Ir nanozyme (termed as Co-Ir/C nanozyme) for the determination of total antioxidant capacity (TAC) in food samples. The Co-Ir/C nanozyme shows excellent durability under extensive pH ranges, high temperature and high salt concentration due to the protection of carbon supporter. It can be recycled by simple magnetic separation, and its catalytic activity remains stable after long-term operation and storage. Taking full advantage of the superior peroxidase-like activity of Co-Ir/C nanozyme, it is used for colorimetric detection of ascorbic acid (or known as vitamin C), an important vitamin to adjust body's normal physiological function, with results showing higher sensitivity (detection limit of 0.27 µM) than most of the recently published works. Moreover, the determination of TAC in vitamin C tablets and fruits are further achieved, which are in good agreement with those of commercial colorimetric test kits. This study helps guide the rational preparation of versatile and highly stable nanozymes, and develops a robust TAC determination platform for future food quality monitoring.

Single-atom-anchored microsweepers for H. pylori inhibition through dynamically navigated reciprocating locomotion.

Catalytic microsweepers with a single-iron-atom center were designed to search for and inhibit Helicobacter pylori. Under dynamic navigation, the microsweepers displayed a large-range wall-adhering reciprocating motion, which increased the opportunity for interaction between microsweepers and H. pylori and further inhibited H. pylori through acid-responsive reactive oxygen species generation.

Geometric characterization of dynamical structure for neural firing activities induced by inhibitory pulse.

In general, inhibitory stimuli are thought to inhibit neuronal firing, but they may actually enhance firing sometimes, such as post-inhibitory rebound spike (PIR spike) and post-inhibitory facilitation (PIF) phenomena, which play an important role in human neuronal activities. We study responses to inhibitory pulse in a classical neuron model (Quartic adaptive Integrate-and-fire model) well known to reproduce a number of biologically realistic behaviors. The three phenomena that we study are PIR, in which a neuron fires after an inhibitory pulse, and PIF, in which a subthreshold excitatory input can induce a spike if it is applied with proper timing after an inhibitory pulse, as well as period firing after inhibitory pulse. When the system features focus and saddle two equilibriums, the three phenomena will be occurred under the inhibitory pulse, while all three phenomena will not be induced when the system features node and saddle two equilibriums. Using dynamical systems theory, we explain the threshold mechanism of enhancement of neural firing response induced by inhibitory pulse and analyze the origin of these phenomena from several factors. We also describe the geometric characterization of dynamical structures of these three phenomena. This study therefore enrich the paradoxical phenomena that induced by inhibitory input and advance our understanding of its role.

An Implantable Magnetic Vascular Scaffold for Circulating Tumor Cell Removal In Vivo.

An integrated trapped device (ITD) capable of removal of circulating tumor cells (CTCs) can assuage or even prevent metastasis. However, adhesion repertoires are ordinarily neglected in the design of ITDs, possibly leading to the omission of highly metastatic CTC and treatment failure. Here a vascular-like ITD with adhesive sites and wireless magnetothermal response to remove highly metastatic CTC in vivo is presented. Such a vascular-like ITD comprises circumferential well-aligned fibers and artificial adhesion repertoires and is optimized for magnetothermal integration. Continuous and repeated capture in a dynamic environment increases capture efficiency over time. Meanwhile, the heat generation of the ITD leads to the capture of CTC death owing to cell heat sensitivity. Furthermore, the constructed bioinspired ultrastructure of the ITD prevents vascular blockage and induces potential vascular regeneration. Overall, this work defines an extendable strategy for constructing adhesion repertoires against intravascular shear forces, provides a vascular-like ITD for reducing CTC counts, and is expected to alleviate the risk of cancer recurrence.

Correlation Analysis of Synchronization Type and Degree in Respiratory Neural Network.

Pre-Bötzinger complex (PBC) is a necessary condition for the generation of respiratory rhythm. Due to the existence of synaptic gaps, delay plays a key role in the synchronous operation of coupled neurons. In this study, the relationship between synchronization and correlation degree is established for the first time by using ISI bifurcation and correlation coefficient, and the relationship between synchronization and correlation degree is discussed under the conditions of no delay, symmetric delay, and asymmetric delay. The results show that the phase synchronization of two coupling PBCs is closely related to the weak correlation, that is, the weak phase synchronization may occur under the condition of incomplete synchronization. Moreover, the time delay and coupling strength are controlled in the modified PBC network model, which not only reveals the law of PBC firing transition but also reveals the complex synchronization behavior in the coupled chaotic neurons. Especially, when the two coupled neurons are nonidentical, the complete synchronization will disappear. These results fully reveal the dynamic behavior of the PBC neural system, which is helpful to explore the signal transmission and coding of PBC neurons and provide theoretical value for further understanding respiratory rhythm.

Dynamics Analysis of Firing Patterns in Pre-Bötzinger Complex Neurons Model.

Pre-Bötzinger complex (PBC) neurons located in mammalian brain are the necessary conditions to produce respiratory rhythm, which has been widely verified experimentally and numerically. At present, one of the two different types of bursting mechanisms found in PBC mainly depends on the calcium-activated of non-specific cation current (I CaN ). In order to study the influence of I CaN and stimulus current I exc in PBC inspiratory neurons, a single compartment model was simplified, and firing patterns of the model was discussed by using stability theory, bifurcation analysis, fast, and slow decomposition technology combined with numerical simulation. Under the stimulation of different somatic applied currents, the firing behavior of neurons are studied and exhibit multiple mix bursting patterns, which is helpful to further understand the mechanism of respiratory rhythms of PBC neurons.

Graphene encapsuled Ru nanocrystal with highly-efficient peroxidase-like activity for glutathione detection at near-physiological pH.

A novel nanozyme comprised of graphene encapsuled Ru nanocrystals (Ru@G) with effective and stable peroxidase-like activity prepared using a chemical vapor deposition (CVD) method was used for the detection of glutathione at near-physiological pH.