The B-DNA double helix can dynamically accommodate G–C and A–T base pairs in either Watson-Crick or Hoogsteen configurations. Here, we show that G–C+ and A–U Hoogsteen base pairs are strongly disfavored in A-RNA. As a result, N1-methyl adenosine and N1-methyl guanosine, which occur in DNA as a form of alkylation damage, and in RNA as a posttranscriptional modification, have dramatically different consequences. They create G–C+ and A–U Hoogsteen base pairs in duplex DNA that maintain the structural integrity of the double helix, but block base pairing all together and induce local duplex melting in RNA, providing a mechanism for potently disrupting RNA structure through posttranscriptional modifications. The markedly different propensities to form Hoogsteen base pairs in B-DNA and A-RNA may help meet the opposing requirements of maintaining genome stability on one hand, and dynamically modulating the structure of the epitranscriptome on the other.

Developing noble metal-free water oxidation catalysts is essential for many energy conversion/storage processes (e.g., water splitting). Herein, we report the facile synthesis of hollow Co3O4 microspheres composed of porous, ultrathin (<5 nm), single-crystal-like nanosheets via a novel "self-template" route. The successful preparation of these hollow Co3O4 nanomaterials includes three main steps: (1) the synthesis of solid cobalt alkoxide microspheres, (2) their subsequent self-template conversion into hollow cobalt hydroxide microspheres composed of ultrathin nanosheets, and finally (3) thermal treatment of hollow cobalt hydroxide microspheres into the hollow Co3O4 material. The as-obtained hollow Co3O4 nanomaterial possesses a high BET surface area (∼180 m(2) g(-1)), and can serve as an active and stable water oxidation catalyst under both electrochemical and photochemical reaction conditions, owing to its unique structural features. In the electrochemical water oxidation, this catalyst affords a current density of 10 mA cm(-2) (a value related to practical relevance) at an overpotential of ∼0.40 V. Moreover, with the assistance of a sensitizer [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine), this nanomaterial can catalyze water oxidation reactions under visible light irradiation with an O2 evolution rate of ∼12 218 μmol g(-1) h(-1). Our results suggest that delicate nanostructuring can offer unique advantages for developing efficient water oxidation catalysts.

Scheme 1. Schematic illustration of the construction of Pt@NH 2-UiO-66 (PU) and Pt@NH 2-UiO-66@MnO x (PUM) samples.

Nitrogen-doped (N-doped) photoluminescent carbon dots (CDs) were prepared by a one-pot microwave-assisted hydrothermal treatment using histidine as the sole carbon source in the absence of acid, alkali, or metal ions. With a diameter of 2-5 nm, the synthesized CDs had apparent lattice fringes and exhibited an excitation-dependent photoluminescent behavior. The CDs were highly yielded, well-dispersed in aqueous solution, and showed high photostability in the solutions of a wide range of pH and salinity. They were used as probes to identify the presence of Fe(3+) ions with a detection limit of 10 nM. With confirmed nontoxicity, these CDs could enter the cancer cells, indicating a practical potential for cellular imaging and labeling.

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To develop potential metal-organic frameworks (MOFs) for 2,4,6-trinitrophenol (TNP) detection, an amino-functionalized Zn-MOF, [NH(CH)][ZnO(bpt)(bdc-NH)]·5DMF (where Hbpt = biphenyl-3,4',5-tricarboxylate, Hbdc-NH = 2-aminoterephthalic acid, and DMF = N,N-dimethylformamide), has been designed theoretically and synthesized experimentally. Its structure is composed of ZnO(CO) secondary building units linked by mixed ligands, exhibiting a three-dimensional framework. Fluorescence exploration revealed that the amino-functionalized Zn-MOF shows high selectivity and sensitivity for TNP, which agrees well with the predictions of theoretical simulations. This work provides a suitable means to develop new potential MOFs for TNP detection performance with a combination of experimental and theoretical perspectives.

Monodisperse water-soluble hexagonal phase Ln(3+)-doped NaGdF(4) upconverting nanocrystals (UCNCs) have been successfully fabricated by means of a fast, facile, and environmentally friendly microwave-assisted route with polyethylenimine as the surfactant. Fine-tuning of the UC emission from visible to near-IR and finally to white light has been achieved. Furthermore, studies of the magnetic resonance imaging as well as the magnetization (magnetization-magnetic field curves) and the targeted recognition properties of FA-coupled amine-functionalized NaGdF(4)@SiO(2) UCNCs indicate that the obtained NaGdF(4) UCNCs can be potential candidates for dual-mode optical/magnetic bioapplications.

A facile solution-phase route for the preparation of AgInSe2 nanocrystals was developed by using silver nitrate, indium stearate, and oleylamine-selenium (OAm-Se) as precursors. The evolution process of the AgInSe2 nanocrystals is discussed in detail and different reaction conditions all have a great impact on the growth and morphology of the nanocrystals. Alloyed AgIn(S1-xSex)2 nanocrystals with controlled composition across the entire range (0 ≤ x ≤ 1) was also successfully prepared by modulating the S/Se reactant mole ratio. X-ray diffraction (XRD), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to confirm that the alloyed AgIn(S1-xSex)2 nanocrystals are homogeneous. The UV-vis absorption spectra revealed that the band gap energies of the alloyed AgIn(S1-xSex)2 nanocrystals could be continuously tuned by increasing the Se content.