Highly Thermostable and Insensitive Energetic Hybrid Coordination Polymers Based on Graphene Oxide–Cu(II) Complex

New highly energetic coordination polymers (ECPs), based on the graphene oxide (GO)-copper­(II) complex, have been synthesized using 5,5′-azo-1,2,3,4-tetrazole (TEZ) and 4,4′-azo-1,2,4-triazole (ATRZ), as linking ligands between GO-Cu layers. The molecular structures, sensitivity, and detonation performances of these ECPs were determined. It was shown that these energetic nanomaterials are insensitive and highly thermostable, due to high heat and impact dissipation capacity of GO sheets. In particular, the GO-TEZ-Cu­(II) ECP shows low sensitivity to impact and electrostatic discharge (<i>I</i>_m = 21 J; ESD of 1995 mJ) and has a comparable detonation performance to RDX. Also, our novel GO/Cu­(II)/ATRZ hybrid ECP GO-Cu­(II)-ATRZ ECP exhibits high density (2.85 g·cm^–3), remarkably high thermostability (<i>T</i>_p = 456 °C), and low sensitivity (<i>I</i>_m > 98 J; ESD of 1000 mJ). The latter material has a calculated detonation velocity of 7082 m·s^–1, which is slightly higher than that of energetic ATRZ-Cu­(II) 3D MOF and higher than one of the top thermostable explosives HNS (<i>T</i>_p = 316 °C; 7000 m s^–1)

Biorecognition Layer Engineering: Overcoming Screening Limitations of Nanowire-Based FET Devices

Detection of biological species is of great importance to numerous areas of medical and life sciences from the diagnosis of diseases to the discovery of new drugs. Essential to the detection mechanism is the transduction of a signal associated with the specific recognition of biomolecules of interest. Nanowire-based electrical devices have been demonstrated as a powerful sensing platform for the highly sensitive detection of a wide-range of biological and chemical species. Yet, detecting biomolecules in complex biosamples of high ionic strength (>100 mM) is severely hampered by ionic screening effects. As a consequence, most of existing nanowire sensors operate under low ionic strength conditions, requiring ex situ biosample manipulation steps, that is, desalting processes. Here, we demonstrate an effective approach for the direct detection of biomolecules in untreated serum, based on the fragmentation of antibody-capturing units. Size-reduced antibody fragments permit the biorecognition event to occur in closer proximity to the nanowire surface, falling within the charge-sensitive Debye screening length. Furthermore, we explored the effect of antibody surface coverage on the resulting detection sensitivity limit under the high ionic strength conditions tested and found that lower antibody surface densities, in contrary to high antibody surface coverage, leads to devices of greater sensitivities. Thus, the direct and sensitive detection of proteins in untreated serum and blood samples was effectively performed down to the sub-pM concentration range without the requirement of biosamples manipulation

Non-covalent Monolayer-Piercing Anchoring of Lipophilic Nucleic Acids: Preparation, Characterization, and Sensing Applications

Functional interfaces of biomolecules and inorganic substrates like semiconductor materials are of utmost importance for the development of highly sensitive biosensors and microarray technology. However, there is still a lot of room for improving the techniques for immobilization of biomolecules, in particular nucleic acids and proteins. Conventional anchoring strategies rely on attaching biomacromolecules via complementary functional groups, appropriate bifunctional linker molecules, or non-covalent immobilization via electrostatic interactions. In this work, we demonstrate a facile, new, and general method for the reversible non-covalent attachment of amphiphilic DNA probes containing hydrophobic units attached to the nucleobases (lipid–DNA) onto SAM-modified gold electrodes, silicon semiconductor surfaces, and glass substrates. We show the anchoring of well-defined amounts of lipid–DNA onto the surface by insertion of their lipid tails into the hydrophobic monolayer structure. The surface coverage of DNA molecules can be conveniently controlled by modulating the initial concentration and incubation time. Further control over the DNA layer is afforded by the additional external stimulus of temperature. Heating the DNA-modified surfaces at temperatures >80 °C leads to the release of the lipid–DNA structures from the surface without harming the integrity of the hydrophobic SAMs. These supramolecular DNA layers can be further tuned by anchoring onto a mixed SAM containing hydrophobic molecules of different lengths, rather than a homogeneous SAM. Immobilization of lipid–DNA on such SAMs has revealed that the surface density of DNA probes is highly dependent on the composition of the surface layer and the structure of the lipid–DNA. The formation of the lipid–DNA sensing layers was monitored and characterized by numerous techniques including X-ray photoelectron spectroscopy, quartz crystal microbalance, ellipsometry, contact angle measurements, atomic force microscopy, and confocal fluorescence imaging. Finally, this new DNA modification strategy was applied for the sensing of target DNAs using silicon-nanowire field-effect transistor device arrays, showing a high degree of specificity toward the complementary DNA target, as well as single-base mismatch selectivity