Liu Deng

Ferrocenoyl Phenylalanine: A New Strategy Toward Supramolecular Hydrogels with Multistimuli Responsive Properties

In this paper we present a new paradigm for designing hydrogelators that exhibit sharp phase transitions in response to a series of disparate stimuli, including oxidation-reduction reactions (redox), guest-host interactions, and pH changes. We have serendipitously discovered that ferrocenoyl phenylalanine (Fc-F) monomers aggregate in water via a rapid self-assembly mechanism to form stable, multistimuli hydrogels. In comparison to other known mono- and multiresponsive gelators, Fc-F is unique because of its small size, economy of gel-forming components, and exceptionally simple molecular structure. Density functional theory (DFT) ab initio calculations suggest gel formation initially involves an antiparallel, noncovalent dimerization step wherein the ferrocenoyl moiety of one axe-like monomer conjoins with the phenyl group of the second monomer via a π-π stacking interaction to form brick-like dimers. This stacking creates a cavity in which the carboxylic acid groups of each monomer mutually interact via hydrogen bond formation, which affords additional stability to the dimer. On the basis of structural analysis via optical and electrical measurements and additional DFT calculations, we propose a possible stepwise hierachical assembly mechanism for fibril formation. Insights into the self-assembly pathway of Fc-F should prove useful for understanding gelation processes of more complex systems. We expect that Fc-F will serve as a helpful archetypical template for others to use when designing new, stimuli specific hydrogelation agents.

Oligonucleotide-stabilized silver nanoclusters as fluorescent probes for sensitive detection of hydroquinone

In this paper, a simple strategy for the sensitive detection of hydroquinone (H2Q) using fluorescent silver nanoclusters (AgNCs) has been developed. In the presence of H2O2 and peroxidase, the fluorescence of AgNCs was quenched efficiently by phenolic compounds. The mechanism inherent in the fluorescence quenching could be mainly ascribed to the formation of the quinone intermediates via enzyme-catalyzed oxidation of phenolic compounds. Combined with the high specificity of the enzyme, the method could determine phenolic compounds with a linear relationship ranging from 8.0 × 10−8 to 3.2 × 10−6 mol L−1 and a detection limit of 10−8 mol L−1. In the case of phenols, the presented sensor may serve as a comparative empirical method for the evaluation of contamination.

Rational Tuning of the Electrocatalytic Nanobiointerface for a “Turn‐Off” Biofuel‐Cell‐Based Self‐Powered Biosensor for p53 Protein

Herein, a novel tunable electrocatalytic nanobiointerface for the construction of a high-sensitivity and high-selectivity biofuel-cell (BFC)-based self-powered biosensor for the detection of transcription factor protein p53 is reported, in which bilirubin oxidase (BOD)/DNA supramolecular modified graphene/platinum nanoparticles hybrid nanosheet (GPNHN) works as a new enhanced material of biocathode to control the attachment of target, and thus tune the electron-transfer process of oxygen reduction for transducing signaling magnification. It is found that in the presence of p53, the strong interaction between the wild-type p53 and its consensus DNA sequence on the electrode surface can block the electron transfer from the BOD to the electrode, thus providing a good opportunity for reducing the electrocatalytic activity of oxygen reduction in the biocathode. This in combination with the glucose oxidation at the carbon nanotube/Meldolas blue/glucose dehydrogenase bioanode can result in a current/or power decrease of BFC in the presence of wild-type p53. The specially designed BFC-based self-powered p53 sensor shows a wide linear range from 1u2005pM to 1u2005μM with a detection limit of 1u2005pM for analyzing wild-type p53. Most importantly, our BFC-based self-powered sensors can detect the concentrations of wild-type p53 in normal and cancer cell lysates without any extensive sample pretreatment/separation or specialized instruments. The present BFC-based self-powered sensor can provide a simple, economical, sensitive, and rapid way for analyzing p53 protein in normal and cancer cells at clinical level, which shows great potential for creating the treatment modalities that capitalize on the concentration variation of the wild-type p53.

From supramolecular hydrogels to functional aerogels: a facile strategy to fabricate Fe3O4/N-doped graphene composites

This manuscript introduces a simple method to fabricate hybrid aerogels with Fe3O4 nanocrystals/nitrogen-doped graphene (Fe3O4/N-GAs) through one-shot self-mineralization of ferrocenoyl phenylalanine/graphene oxide (Fc-F/GO) supramolecular hydrogels. We found that GO could trigger a sol–gel transition of Fc-F gelators below the critical gelation concentration and the electron microscopic results revealed that the self-assembled Fc-F fibrils tightly bound onto graphene sheets. Upon hydrothermal reaction, Fc moieties in these fibrils could be locally oxidized to Fe3O4 nanocrystals by GO, remaining on the top of reduced GO (RGO) sheets and therefore inhibiting the self-aggregation of graphene nanosheets. After drying, the remains of the supramolecular hybrid hydrogels are presented as the three-dimensional (3D) framework of ultra-thin graphene sheets on which Fe3O4 nanoparticles (NPs) are uniformly immobilized as single crystals. Since the new born Fe3O4 nanocrystals are closely anchored on the graphene sheets, the as-prepared Fe3O4/N-GAs complex shows excellent electrocatalytic activity for the oxygen reduction reaction (ORR, compared to commercial Pt/C). Notably, the Fc-F/GO supramolecular hydrogels act as multifunctional reagents, such as capping agents for preventing graphene nanosheets from stacking and Fe and N sources for Fe3O4/N-GAs. We expect that this intriguing strategy can provide a useful archetypical example in designing nonprecious metal oxides/carbon hybrid materials to serve as substitutes for noble metal catalysts.

A facile way to achieve all-photonic logic functions and photo-printing based on a donor–acceptor Stenhouse adduct

Herein, a simple bi-photochromic molecule containing a donor–acceptor Stenhouse adduct and azobenzene moiety was synthesized. It can achieve all-photonic multimolecular logic functions and photo-printing. This molecule could provide a novel platform for exploring multifunctional molecular logic devices.

MOF-Templated Fabrication of Hollow Co4N@N-Doped Carbon Porous Nanocages with Superior Catalytic Activity

Metallic Co4N catalysts have been considered as one of the most promising non-noble materials for heterogeneous catalysis because of their high electrical conductivity, great magnetic property, and high intrinsic activity. However, the metastable properties seriously limit their applications for heterogeneous water phase catalysis. In this work, a novel Co-metal-organic framework (MOF)-derived hollow porous nanocages (PNCs) composed of metallic Co4N and N-doped carbon (NC) were synthesized for the first time. This hollow three-dimensional (3D) PNC catalyst was synthesized by taking advantage of Co-MOF as a precursor for fabricating 3D hollow Co3O4@C PNCs, along with the NH3 treatment of Co-oxide frames to promote the in situ conversion of Co-MOF to Co4N@NC PNCs, benefiting from the high intrinsic activity and electron conductivity of the metallic Co4N phase and the good permeability of the hollow porous nanostructure as well as the efficient doping of N into the carbon layer. Besides, the covalent bridge between the active Co4N surface and PNC shells also provides facile pathways for electron and mass transport. The obtained Co4N@NC PNCs exhibit excellent catalytic activity and stability for 4-nitrophenol reduction in terms of low activation energy (Ea = 23.53 kJ mol-1), high turnover frequency (52.01 × 1020 molecule g-1 min-1), and high apparent rate constant (kapp = 2.106 min-1). Furthermore, its magnetic property and stable configuration account for the excellent recyclability of the catalyst. It is hoped that our finding could pave the way for the construction of other hollow transition metal-based nitride@NC PNC catalysts for wide applications.

An ultrasensitive colorimetric aptasensor for ATP based on peptide/Au nanocomposites and hemin–G-quadruplex DNAzyme

A peptide nanosphere-based colorimetric aptasensor for the ultrasensitive detection of adenosine triphosphate (ATP) has been fabricated. By conjugating gold nanoparticles (AuNPs) onto peptide nanospheres (PNS), the PNS/AuNPs nanocomposite was obtained and used as a carrier for single-strand ATP aptamer (S1) and signaling DNAzyme sequence. In the presence of ATP, the nucleic acids decorated PNS/AuNPs could immobilize to a 96-well plate which was modified with another single-strand ATP aptamer (S2) DNA. Then, upon addition of K+ and hemin, the designed signaling DNAzyme sequence on PNS/AuNPs could form the hemin–G-quadruplex DNAzyme and catalyze the conversion of TMB to coloured TMB2+. The colorimetric aptasensor adopting PNS/AuNPs nanocomposites as signal enhancers possesses much higher sensitivity towards ATP compared with the conventional AuNPs-based aptasensors. The PNS/AuNPs-based sensor is available for sensitively detecting ATP in a concentration range of 0.01–1 nM with a detection limit of 1.35 pM. Moreover, the constructed aptasensor displayed excellent selectivity for ATP over other analogues such as GTP, CTP and UTP. The proposed strategy for the construction of an aptasensor based on nanocomposites has great potential to become a universal technique for developing various aptasensors by using different aptamers.

Fabrication of Surface Protein-Imprinted Biofuel Cell for Sensitive Self-Powered Glycoprotein Detection

Glycoproteins are important biomarkers and therapeutic targets in clinical diagnostics. The conventional analytical methods for glycoprotein are usually faced with some challenges, such as the complex pretreatment of samples, poor availability, and limited stability of antibody, making them not suitable for point-of-care and on-site application. Herein, we demonstrate a novel miniaturized biofuel cells (BFCs)-based self-powered nanosensor for the specific and sensitive determination of glycoproteins in complex samples through the combination of boronate-affinity molecularly imprinted polymer (MIP) and the boronate affinity functionalized biliroxidase-carbon nanotube nanocomposites. The above MIP and the nanocomposites act as both signal probe and biocatalyst at the cathode. The as-obtained self-powered MIP-BFC-based biosensor can detect horseradish peroxidase (a type of glycoprotein) with a wide linear range of 1 ng/mL to 10 μg/mL and a very low detection limit of 1 ng/mL. Especially, it shows high tolerance for different interferences (e.g., sugars and other glycoproteins) and can even measure the α-fetoprotein level in serum samples. Moreover, it exhibits significant advantages over the conventional assays in terms of cost efficiency, stability, and speed, especially inexpensive instrument needed. Our novel approach for construction of the sensor paves a simple and economical way to fabricate portable devices for point-of-care and on-site application.

Biomimetic nanothylakoids for efficient imaging-guided photodynamic therapy for cancer

Biomimetic nanothylakoids, which are constructed from the thylakoid membrane of vegetable leaves, show high efficiency in tumor microenvironment modulation and photodynamic antitumor therapy under near infrared fluorescence guidance. Furthermore, their outstanding biosafety, facile preparation and low cost make nanothylakoids suitable for further clinical applications.