Liyan Zheng

Electrochemiluminescence of Water-Soluble Carbon Nanocrystals Released Electrochemically from Graphite

Water-soluble carbon nanocrystals (CNCs) with electrochemiluminescence (ECL) activity were released into aqueous solution from a graphite rod by applying a scanning potential. ECL emission of CNCs observed during their preparation probably provides a useful method for monitoring and screening nanocrystal preparation. The ECL behavior and its mechanism in CNCs have been studied in detail for the first time. The results suggest promising applications of CNCs in the development of new types of biosensors and display devices in the future on the basis of their strong and stable ECL emission, good stability, low cytotoxicity, excellent water solubility, easy labeling, and environmental friendliness.

Microstructured Graphene Arrays for Highly Sensitive Flexible Tactile Sensors

A highly sensitive tactile sensor is devised by applying microstructured graphene arrays as sensitive layers. The combination of graphene and anisotropic microstructures endows this sensor with an ultra-high sensitivity of -5.53 kPa(-1) , an ultra-fast response time of only 0.2 ms, as well as good reliability, rendering it promising for the application of tactile sensing in artificial skin and human-machine interface.

Encapsulation of strongly fluorescent carbon quantum dots in metal-organic frameworks for enhancing chemical sensing.

Novel highly fluorescent (FL) metal-organic frameworks (MOFs) have been synthesized by encapsulating branched poly-(ethylenimine)-capped carbon quantum dots (BPEI-CQDs) with a high FL quantum yield into the zeolitic imidazolate framework materials (ZIF-8). The as-synthesized FL-functionalized MOFs not only maintain an excellent FL activity and sensing selectivity derived from BPEI-CQDs but also can strongly and selectively accumulate target analytes due to the adsorption property of MOFs. The selective accumulation effect of MOFs can greatly amplify the sensing signal and specificity of the nanosized FL probe. The obtained BPEI-CQDs/ZIF-8 composites have been used to develop an ultrasensitive and highly selective sensor for Cu(2+) ion, with a wide response range (2-1000 nM) and a very low detection limit (80 pM), and have been successfully applied in the detection of Cu(2+) ions in environmental water samples. It is envisioned that various MOFs incorporated with FL nanostructures with high FL quantum yields and excellent selectivity would be designed and synthesized in similar ways and could be applied in sensing target analytes.

Sericin for resistance switching device with multilevel nonvolatile memory.

Resistance switching characteristics of natural sericin protein film is demonstrated for nonvolatile memory application for the first time. Excellent memory characteristics with a resistance OFF/ON ratio larger than 10(6) have been obtained and a multilevel memory based on sericin has been achieved. The environmentally friendly high performance biomaterial based memory devices may hold a place in the future of electronic device development.

Encapsulation of Hemin in Metal-Organic Frameworks for Catalyzing the Chemiluminescence Reaction of the H2O2-Luminol System and Detecting Glucose in the Neutral Condition.

Novel metal-organic frameworks (MOFs) based solid catalysts have been synthesized by encapsulating Hemin into the HKUST-1 MOF materials. These have been first applied in the chemiluminescence field with outstanding performance. The functionalized MOFs not only maintain an excellent catalytic activity inheriting from Hemin but also can be cyclically utilized as solid mimic peroxidases in the neutral condition. The synthesized Hemin@HKUST-1 composites have been used to develop practical sensors for H2O2 and glucose with wide response ranges and low detection limits. It was envisioned that catalyst-functionalized MOFs for chemiluminescence sensing would have promising applications in green, selective, and sensitive detection of target analytes in the future.

Bio-inspired antireflective hetero-nanojunctions with enhanced photoactivity

A bio-inspired antireflective hetero-nanojunction structure has been fabricated by the hydrothermal growth of ZnO nanorods on silicon micro-pyramids. It has been shown that this structure suppresses light reflection more effectively resulting in a high photocurrent response and good charge separation simultaneously. The strategy provides a means to enhance solar energy conversion.

Fast, Sensitive, and Selective Ion-Triggered Disassembly and Release Based on Tris(bipyridine)ruthenium(II)-Functionalized Metal–Organic Frameworks

Metal-organic frameworks (MOFs) are microporous materials assembled from metal ions and organic linkers. Recently, many studies have been focused on the syntheses of MOFs with permanent porosity for various applications. However, no attention has been paid to controllable disassembly of MOFs and related applications. In this work, for the first time we synthesized novel tris(bipyridine)ruthenium(II)-functionalized MOFs (i.e., RuMOFs) that could be ion-responsively disassembled and release massive guest materials loaded in the frameworks. The synthesized RuMOFs exhibited much stability in aqueous solutions containing H(+), and many metal ions, but could be selectively and sensitively disassembled by Hg(2+) ions, resulting in the release of large quantities of Ru(bpy)3(2+). The target-responsive release mechanism was investigated and discussed in detail. On the basis of the ion-responsive disassembly and release, an ultrasensitive electrochemiluminescence sensing method for Hg(2+) has been developed with a very low limit of detection (5.3 × 10(-13) M). It was envisioned that the RuMOFs and similar target-responsive functional MOF materials would have promising applications in ultrasensitive and highly selective chemical sensing and even in accurately controllable drug delivering and releasing.

Optoelectronics of Organic Nanofibers Formed by Co‐Assembly of Porphyrin and Perylenediimide

Organic nanofibers are formed by simple ionic co-assembly of positively charged porphyrin (electron donor) and negatively charged perylenediimide (electron acceptor) derivatives in aqueous solution. Two kinds of electron transfer routes between electron donor and electron acceptor under light excitation in nanofibers are confirmed by DFT calculations and experimental data.

Preparation of Protein-like Silver–Cysteine Hybrid Nanowires and Application in Ultrasensitive Immunoassay of Cancer Biomarker

Novel protein-like silver-cysteine hybrid nanowires (p-SCNWs) have been synthesized by a green, simple, nontemplate, seedless, and one-step aqueous-phase approach. AgNO3 and l-cysteine were dissolved in distilled water, forming Ag-cysteine precipitates and HNO3. Under vigorous stirring, the pH of the solution was rapidly adjusted to 9.0 by addition of concentrated sodium hydroxide solution, leading to quick dissolution of the Ag-cysteine precipitates and sudden appearance of white precipitates of p-SCNWs. The p-SCNWs are monodispersed nanowires with diameter of 100 nm and length of tens of micrometers, and have abundant carboxyl (-COOH) and amine (-NH2) groups at their surfaces, large amounts of peptide-linkages and S-bonding silver ions (Ag(+)) inside, making them look and act like Ag-hybrid protein nanostructures. The abundant -COOH and -NH2 groups at the surfaces of p-SCNWs have been found to facilitate the reactions between the p-SCNWs and proteins including antibodies. Furthermore, the fact that the p-SCNWs contain large amounts of silver ions enables biofunctionalized p-SCNWs to be excellent signal amplifying chemiluminescence labels for ultrasensitive and highly selective detection of important antigens, such as cancer biomarkers. In this work, the immunoassay of carcinoembryonic antigen (CEA) in human serum was taken as an example to demonstrate the immunoassay applications of antibody-functionalized p-SCNWs. By the novel p-SCNW labels, CEA can be detected in the linear range from 5 to 400 fg/mL with a limit of detection (LOD) of 2.2 fg/mL (at signal-to-noise ratio of 3), which is much lower than that obtained by commercially available enzyme-linked immunosorbent assay (ELISA). Therefore, the synthesized p-SCNWs are envisioned to be an excellent carrier for proteins and related immunoassay strategy would have promising applications in ultrasensitive clinical screening of cancer biomarkers for early diagnostics of cancers.

Sensitive detection of mercury and copper ions by fluorescent DNA/Ag nanoclusters in guanine-rich DNA hybridization

In this work, we designed a new fluorescent oligonucleotides-stabilized silver nanoclusters (DNA/AgNCs) probe for sensitive detection of mercury and copper ions. This probe contains two tailored DNA sequence. One is a signal probe contains a cytosine-rich sequence template for AgNCs synthesis and link sequence at both ends. The other is a guanine-rich sequence for signal enhancement and link sequence complementary to the link sequence of the signal probe. After hybridization, the fluorescence of hybridized double-strand DNA/AgNCs is 200-fold enhanced based on the fluorescence enhancement effect of DNA/AgNCs in proximity of guanine-rich DNA sequence. The double-strand DNA/AgNCs probe is brighter and stable than that of single-strand DNA/AgNCs, and more importantly, can be used as novel fluorescent probes for detecting mercury and copper ions. Mercury and copper ions in the range of 6.0-160.0 and 6-240 nM, can be linearly detected with the detection limits of 2.1 and 3.4 nM, respectively. Our results indicated that the analytical parameters of the method for mercury and copper ions detection are much better than which using a single-strand DNA/AgNCs.