Latest ArticlesSurface-enhanced Raman spectroscopy (SERS), a powerful surface vibrational spectroscopic technique, is ideally suited for in situ monitoring the chemical transformations occurred at surfaces and/or interfaces. For in situ SERS monitoring, a platform integrated both plasmonic and catalytic activity is a prerequisite. Here, we fabricate a bifunctional Au-Pd nanocoronal film for in situ SERS monitoring Suzuki-Miyaura cross-coupling reaction. This excellent bifunctional substrate leads to the coupling of high catalytic activity with a strong SERS effect at the center of two adjacent Au cores and shows fine reproducibility and stability of SERS signals. During investigating the Suzuki reaction with in situ SERS, we found two distinct catalytic kinetic processes resulted from two disparate catalytic sites on a Au-Pd nanocoronal. Comparing with conventional analytical techniques, this work provides a novel approach for studying Suzuki reactions at surfaces and/or interfaces with in situ SERS.
The conversion of traditional polymolybdate-based metal-organic frameworks (POMOFs) crystals to well-aligned nanoarrays are highly attractive for electrocatalytic hydrogen evolution but remains significant challenge. Herein, we demonstrated that the POMOFs nanoarrays as self-supported electrode toward hydrogen evolution with high catalytic activity and stability. Single-crystal X-ray analysis reveal the {ε-PMo8VMo4VIO37Zn4} (Zn-ε-Keggin) serve as secondary building blocks and directly connected to BPB organic ligands (BPB = 1, 4-bis(pyrid-4-yl)benzene) to obtain novel [ε-PMo8VMo4VIO37(OH)3Zn4][BPB]3 (named as ZnMo-POMOF). Particularly, ZnMo-POMOF nanoflower arrays grown in-situ on a Ni foam substrate exhibiting excellent electrocatalytic hydrogen evolution performance of 180 mV at a current density of 10 mA/cm2 with the Tafel slope of 66 mV/dec, thus among one of the best POMOF-based electrocatalysts reported so far. DFT calculations reveal that the bridging oxygen active sites (Oa) significantly optimizes Gibbs free energy of H* adsorption for Zn-ε-Keggin polymolybdate units (−0.07 eV), thereby increasing the intrinsic activity of the ZnMo-POMOF.
Chemodynamic therapy (CDT) is a promising therapeutic approach for in situ cancer treatment, but it is still hindered by inefficient single-modality treatment and the weak targeted delivery of reagents into mitochondria (the main site of intracellular ROS production). Herein, to obtain a multimodal strategy, peptide-assembled siRNA nanomicelles were prepared to confine ultrasmall MnO in small silica cages (silicages), which is convenient for synergistic chemical and gene-regulated cancer therapy. Given the free energy and versatility of small silicages, as well as the excellent Fenton-like activity of ultrasmall MnO, MnO-inside-loaded silicages (10 nm) were prepared for CDT delivery to mitochondria. Subsequently, to obtain a synergistic CDT and gene silencing treatment, the peptide-mediated assembly of siRNA and MnO-loaded silicages were employed to obtain silicage@MnO-siRNA nanomicelles (SMS NMs). After multiple modifications, sequential cancer cell-targeted delivery, GSH-controlled reagent release of siRNA and mitochondria-targeted delivery of MnO-loaded silicages were successfully achieved. Finally, by both in vitro and in vivo experiments, SMS NMs were confirmed to be effective for synergistic chemical and gene-regulated cancer therapy. Our findings expand the applications of silicages and initiate the development of multimodal CDT.
Hydrogel-based quasi-solid-state electrolytes (Q-SSEs) swollen with electrolyte solutions are important components in stretchable supercapacitors and other wearable devices. This work fabricates a super-tough, fatigue-resistant, and alkali-resistant multi-bond network (MBN) hydrogel aiming to be an alkaline Q-SSE. To synthesize the hydrogel, a 2-ureido-4[1H]-pyrimidone (UPy) motif is introduced into a poly(acrylic acid) polymer chain. The obtained MBN hydrogels with 75 wt% water content exhibit tensile strength as high as 2.47 MPa, which is enabled by the large energy dissipation ability originated from the dissociation of UPy dimers due to their high bond association energy. Owing to the high dimerization constant of UPy motifs, the dissociated UPy motifs are able to partially re-associate soon after being released from external forces, resulting in excellent fatigue-resistance. More importantly, the MBN hydrogels exhibit excellent alkali-resistance ability. The UPyGel-10 swollen with 1 mol/L KOH display a tensile strength as high as ~1.0 MPa with elongation at break of ~550%. At the same time, they show ionic conductivity of ~17 mS/cm, which do not decline even when the hydrogels are stretched to 500% strain. The excellent mechanical property and ionic conductivity of the present hydrogels demonstrate potential application as a stretchable alkaline Q-SSE.
T4 polynucleotide kinase (T4 PNK) is a pivotal enzyme for DNA replication, recombination, and DNA damage repair. Herein, a robust single particle counting-based assay has been developed for the high-sensitive determination of T4 PNK activity through only a simple one-step reaction. Taking benefit of the exceptional space-confined enzymatic property of T4 PNK towards DNA substrates on a single nanoparticle, the T4 PNK activity can be precisely determined by counting the fluorescence-positive nanoparticles in a digital manner with a total internal reflection fluorescent microscope (TIRFM). Due to the featured spatial-confined enzymatic property of T4 PNK and the single particle counting-based signal readout, T4 PNK can be effectively differentiated from other interfering enzymes. This facile strategy has been also successfully applied to screen T4 PNK inhibitor and accurately determine T4 PNK activity in complex biological samples, paving a potential avenue for the digital analysis of biomarkers.
To explore the lead-free key scientific issue in perovskite, double perovskite based on AgBi and CuBi was naturally selected as a competitive candidate due to its fascinating functional features, such as self-powered circularly polarized light detection, X-ray detection, photoluminescence and so on. However, the most challenging point is to simulate the structure and function of traditional lead-based perovskite in new double perovskite. At the same time, there are few suitable double perovskite systems with optical and electrical potential. The above two points greatly limit the competitiveness of double perovskite. In order to solve this problem, firstly, by analyzing and comparing previous studies, we used 2,2-dimethylpropan-1-aminium (abbreviated as 2,2-DPA) as the organic template to assemble materials. Solid-to-solid phase transition materials (2,2-DPA)3Bi2I9 1 and (2,2-DPA)3Pb2I7 2 were constructed. Along the path of lead-free and two-dimensional maintenance, we successfully synthesized (2,2-DPA)4AgBiI8·H2O 3 and (2,2-DPA)4CuBiI8·H2O 4. As two typical semiconductors, 3 and 4 with narrower optical band gaps of 1.98 and 1.76 eV show obvious photo-response when the xenon lamp with intensity of 20 mW/cm2 is on or off, implying that they may be applied to light-harvesting and light-detecting devices. By referring to the phase transition mechanism of 1 and 2, 3 may be caused by ordered-disordered transition of the organic part, which was proven to be the first solid-to-solid phase transition material with <100> -oriented layered double perovskites with n = 1 by systematic characterization methods after dehydration for all we know. We believed that this work can provide meaningful guidance for the development of lead-free double perovskites.
Fluorescent dyes with fluorescence emission above 700 nm are favorable for bio-imaging due to the higher tissue transparency and lower background fluorescence. In this study, we present a meso-benzimidazole-pyronin platform (SiBMs) with fluorescence emission maxima above 700 nm, which possess good cell permeability, photostability, and lysosomal localization. The great photophysical properties of the SiBMs encouraged us to further exploit their application toward bio-imaging. We synthesized the reduced 'dihydro' derivative HSiBM3 for sensing ONOO−, with high selectivity and sensitivity and a fast fluorescence "off-on" response (within 2 s). Then, we confirmed the potential of HSiBM3 for visualizing exogenous and endogenous ONOO− in cells and mice. More importantly, HSiBM3 was successfully employed for visualizing acute-liver-injury-induced peroxynitrite.
Pyrylium salts are a type of representative and convincing example of versatility and variety not only as a nodal point in organic transformations but also as an attractive building block in functional organic materials. Herein, we report an effective synthetic protocol to fabricate a new pyrylium-containing porous organic polymers (POPs), named TMP-P, via Knoevenagel condensation with 2,4,6-trimethylpyrylium salt (TMP) as the key building block and 1,4-phthalaldehyde as the linker. The resulting ionic polymer TMP-P exhibited efficient visible-light-driven heterogeneous photodegradation of Rhodamine B, owing to the presence of wide visible light absorption and a narrow optical band gap triggered pyrylium core in the framework.
Rechargeable aqueous Zn/MnO2 batteries raise massive research activities in recent years. However, both the working principle and the degradation mechanism of this battery chemistry are still under debate. Herein, we provide an in-depth electrochemical and structural investigation on this controversial issue based on α-MnO2 crystalline nanowires. Mechanistic analysis substantiates a two-electron reaction pathway of Mn2+/Mn4+ redox couple from part of MnO2 accompanying with a reversible precipitation/dissolution of flaky zinc sulfate hydroxide (ZSH) during the discharge/charge processes. The formation of the ZSH layer is double-edged, which passivates the deep dissolution of MnO2 upon discharging, but promotes the electrochemical deposition kinetics of active MnO2 upon charging. The cell degradation originates primarily from the corrosion failure of metallic zinc anode and the accumulation of irreversible ZnMn2O4 phases on the cathode. The addition of MnSO4 to the electrolyte could afford supplementary capacity contribution via electro-oxidation of Mn2+. However, a high MnSO4 concentration will expedite the cell failure by corroding the metallic zinc anodes. The present study will shed a fundamental insight on developing new strategies toward practically viable Zn/MnO2 batteries.
Mulit-enzyme cascades are a major type of chemical transformations and play a crucial role in biological signal transduction and metabolism. Herein, a trienzyme cascade-triggered fluorescent immunosensor platform was constructed by sequentially integrating alkaline phosphatase (ALP), tyrosinase (TYR) and horseradish peroxidase (HRP). The proposed platform was based on HRP-induced a rapid in situ fluorogenic reaction between dopamine (DA) and 1,5-dihydroxynaphthalene (DHA) to produce a strong yellow azamonardine fluorescent compound (AFC). The obtained AFC was clearly characterized by high-resolution mass spectrum, 1H NMR, 13C NMR and theoretical calculations. The integration of the two-enzyme system (TYR and HRP) or three-enzyme system (ALP, TYR and HRP) led to a maximum of 400.0-fold and 250.0-fold fluorescence enhancements, respectively. Using cardiac troponin Ⅰ (cTnI) as the model antigen, a trienzyme cascade-triggered fluorescent immunosensor platform was developed for quantitative detecting cTnI in a wide linear range from 2 ng/mL to 150 ng/mL with a detection limit of 0.67 ng/mL. In addition, the proposed platform was successfully applied in detection of cTnI in serum of clinical patients. Overall, the developed fluorescent immunosensor performs powerful implications for researching enzyme cascade systems in the field of biomedicine.
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