In modern nanotechnology one of the most exciting areas is the interaction between inorganic quantum dots and biological structures. For instance gold clusters surrounded by a shell of organic ligands covalently attach to proteins or other biological substances and can be used for labeling in structural biology. In the present report we show the possibility of using live plants for the fabrication of nanoparticles. Alfalfa plants were grown in an AuCl 4 rich environment. The absorption of Au metal by the plants was confirmed by X-ray absorption studies (XAS), and transmission electron microscopy (TEM). Atomic resolution analysis confirmed the nucleation and growth of Au nanoparticles inside the plant and that the Au nanoparticles are in a crystalline state. Images also showed defects such as twins in the crystal structure, and in some cases icosahedral nanoparticles were found. X-ray EDS studies corroborated that the nanoparticles are pure gold. This is the first report on the formation of gold nanoparticles by living plants and opens up new and exciting ways to fabricate nanoparticles. It shows how it is possible to link materials science and biotechnology in the new emerging field of nanobiotechnology.

The preparation and study of quantum dots and quantum wires play a very important role in nanotechnology. In this particular study, we report on the uptake of silver by living alfalfa plants. X-ray absorption spectroscopy and transmission electron microscopy (TEM) studies corroborated silver metal uptake by alfalfa plants from a silver-rich solid medium and the subsequent formation of silver nanoparticles. Silver nanoparticle alignment, structure, and coalescence were observed using TEM with an atomic resolution analysis. Dark field image TEM showed the connection of silver nanoparticles of different sizes by possibly noncrystalline silver atomic wires. To our knowledge, this is the first report on the formation of silver nanoparticles by a living plant system.

A porous hydrogen-bonded organic framework (HOF) responsive to acid was constructed from a hexaazatrinaphthylene derivative with carboxyphenyl groups (CPHATN). Precise structures of both 1,2,4-trichlorobenzene solvate [CPHATN-1(TCB)] and activated HOF with permanent porosity (CPHATN-1a) were successfully determined by single-crystalline X-ray diffraction analysis. Permanent porosity of CPHATN-1a was evaluated by gas sorption experiments at low temperature. CPHATN-1a also shows significant thermal stability up to 633 K. Its crystals exhibit a rich photochemistry thanks to intramolecular charge-transfer and interunit proton-transfer reactions. Femtosecond (fs) experiments on crystals demonstrate that these events occur in ≤200 fs and 1.2 ps, respectively. Moreover, single-crystal fluorescence microscopy reveals a shift of the emission spectra most probably as a result of defects and a high anisotropic behavior, reflecting an ordered crystalline structure with a preferential orientation of the molecular dipole moments. Remarkably, CPHATN-1a, as a result of the protonation of pyradyl nitrogen atoms embedded in its π-conjugated core, shows reversible vapor acid-induced color changes from yellow to reddish-brown, which can be also followed by an ON/OFF of its emission. To the best of our knowledge, this is the first HOF that exhibits acid-responsive color changes. The present work provides new findings for developing stimuli responsive HOFs.

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Hydrogen-bonded organic frameworks (HOFs) have drawn unprecedented interest because of their high crystallinity as well as facile process for construction, deconstruction, and reassembly arising from reversible bond formation-dissociation. However, structural fragility and low stability frequently prevent formation of robust HOFs with permanent porosity. Here, we report that hexakis(4-carboxyphenyl)-hexaazatriphenylene (CPHAT) forms three dimensionally networked H-bonded framework CPHAT-1. Interestingly, the activated framework CPHAT-1 a retains not only permanent porosity but single-crystallinity, enabling precise structural characterization and property evaluation on a single crystal. Moreover, CPHAT-1 a retains its framework up to 339 °C or in hot water and in acidic aqueous solution. These results clearly show that even a simple H-bonding motif can be applied for the construction of robust HOFs, which creates a pathway to establish a new class of porous organic frameworks. We also characterize its uptake of gases and I , in addition to a detailed photophysical study (spectroscopy and dynamics of proton and charge transfers) of its unit in solution, and of its single crystal under fluorescence microscopy, in which we observed a marked strong anistropy and narrow distribution. The results bring new findings to the area of HOFs and their possible applications in science and technology.

Enhancing thermal and chemical durability and increasing surface area are two main directions for the construction and improvement of the performance of porous hydrogen-bonded organic frameworks (HOFs). Herein, a hexaazatriphenylene (HAT) derivative that possesses six carboxyaryl groups serves as a suitable building block for the systematic construction of thermally and chemically durable HOFs with high surface area through shape-fitted docking between the HAT cores and interpenetrated three-dimensional network. A HAT derivative with carboxybiphenyl groups forms a stable single-crystalline porous HOF that displays protic solvent durability, even in concentrated HCl, heat resistance up to 305 °C, and a high Brunauer-Emmett-Teller surface area [SA ] of 1288 m g . A single crystal of this HOF displays anisotropic fluorescence, which suggests that it would be applicable to polarized emitters based on robust functional porous materials.

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The T12-apo-based HOF shows a dependence of its emission spectra and lifetimes on the crystal size, where π–π interactions and H-bond networks are paramount to its crystalline nature and photobehaviour.