DNA has been used as a scaffold to stabilize small, atomically monodisperse silver nanoclusters, which have attracted attention due to their intriguing photophysical properties. Herein, we describe the X‐ray crystal structure of a DNA‐encapsulated, near‐infrared emitting Ag16 nanocluster (DNA–Ag16NC). The asymmetric unit of the crystal contains two DNA–Ag16NCs and the crystal packing between the DNA–Ag16NCs is promoted by several interactions, such as two silver‐mediated base pairs between 3′‐terminal adenines, two phosphate–Ca2+–phosphate interactions, and π‐stacking between two neighboring thymines. Each Ag16NC is confined by two DNA decamers that take on a horse‐shoe‐like conformation and is almost fully shielded from the solvent environment. This structural insight will aid in the determination of the structure/photophysical property relationship for this class of emitters and opens up new research opportunities in fluorescence imaging and sensing using noble‐metal clusters.

Intersubband transition (ISBT) in the wavelength range from 1.08 to 1.61 μm was systematically investigated in (GaN)m/(AlN)n superlattices (SLs), grown directly on (0001) sapphire substrates by rf-plasma molecular beam epitaxy. The SLs consisted of 90 periods of GaN wells (m=2∼10 monolayers (ML) in thickness) and AlN barriers (n∼11 ML). One ML corresponds to a thickness of around 2.6 Å. For a 3.3 ML GaN well, the ISBT absorption wavelength reached a minimum of 1.08 μm, close to a theoretically predicted limitation, and it increased monotonically up to 1.61 μm with increasing well thickness to 9.5 ML. We observed absorption spectra as narrow as 61 and 66 meV in linewidth for 1.55 and 1.37 μm samples, respectively.

No abstract