It has been a long-standing challenge to produce air-stable few- or monolayer samples of phosphorene because thin phosphorene films degrade rapidly in ambient conditions. Here we demonstrate a new highly controllable method for fabricating high quality, air-stable phosphorene films with a designated number of layers ranging from a few down to monolayer. Our approach involves the use of oxygen plasma dry etching to thin down thick-exfoliated phosphorene flakes, layer by layer with atomic precision. Moreover, in a stabilized phosphorene monolayer, we were able to precisely engineer defects for the first time, which led to efficient emission of photons at new frequencies in the near infrared at room temperature. In addition, we demonstrate the use of an electrostatic gate to tune the photon emission from the defects in a monolayer phosphorene. This could lead to new electronic and optoelectronic devices, such as electrically tunable, broadband near infrared lighting devices operating at room temperature.

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The vibrations in the azido-, N3, asymmetric stretching region of 2′-azido-2′-deoxyuridine (N3dU) are examined by two-dimensional infrared spectroscopy. In water and tetrahydrofuran (THF), the spectra display a single sharp diagonal peak that shows solvent sensitivity. The frequency-frequency correlation time in water is 1.5 ps, consistent with H-bond making and breaking dynamics. The 2D IR spectrum is reproduced for N3dU in water based on a model correlation function and known linear response functions. Its large extinction coefficient, vibrational frequency outside the protein and nucleic acid IR absorption, and sensitivity to water dynamics renders -N3 a very useful probe for 2D IR and other nonlinear IR studies: its signal is ca. 100 times that of nitrile.

The production of a broadband supercontinuum spanning from 1.8 μm to >7.5 μm is reported which was created by pumping a chalcogenide glass waveguide with ≈320 fs pulses at 4 μm. The total power was ≈20 mW and the source brightness was > ×100 that of current synchrotrons. This source promises to be an excellent laboratory tool for infrared microspectroscopy. 2000 4000 6000 8000 -40 -30 -20 -10 0 Wavelength (nm) Relative power (dB) 3260W 1640W 815W 450W 100W

We report the characteristics of low-loss chalcogenide waveguides for sensing in the mid-infrared (MIR). The waveguides consisted of a Ge₁₁.₅As₂₄Se₆₄.₅ rib waveguide core with a 10nm fluoropolymer coating on a Ge₁₁.₅As₂₄S₆₄.₅ bottom cladding and were fabricated by thermal evaporation, photolithography and ICP plasma etching. Over most of the functional group band from 1500 to 4000 cm⁻¹ the losses were < 1 dB/cm with a minimum of 0.3 dB/cm at 2000 cm⁻¹. The basic capabilities of these waveguides for spectroscopy were demonstrated by measuring the absorption spectrum of soluble Prussian blue in Dimethyl Sulphoxide.

By pumping an 11-cm-long step-index chalcogenide fiber with ∼330  fs pulses at 4.0 μm from an optical parametric amplifier, mid-infrared supercontinuum generation spanning from ∼1.8 to ∼10  μm within a dynamic range of ±15  dB has been demonstrated at a relatively low power threshold of ∼3000  W.

Davies B, "Experimental demonstration of linearly polarized 2-10 μm supercontinuum generation in a chalcogenide rib waveguide", Optics Letters 41, 5(2016) 958-961. Luther-Davies B, "High brightness 2.2-12 μm mid-infrared supercontinuum generation in a nontoxic chalcogenide step-index fiber", Journal of the American Ceramic Society, 99, 8 (2016) 2565-2568. 3.Madden S, "High Q factor chalcogenide ring resonators for cavityenhanced MIR spectroscopic sensing", Optics Express 23, 15 (2015)

The synthesis of 2′-azido-5-cyano-2′-deoxyuridine, N3CNdU (1), from trityl-protected 2′-amino-2′-deoxyuridine was accomplished in four steps with a 12.5% overall yield. The IR absorption positions and profiles of the azide and nitrile group of N3CNdU were investigated in 14 different solvents and water/DMSO solvent mixtures. The azide probe was superior to the nitrile probe in terms of its extinction coefficient, which is 2–4 times larger. However, the nitrile IR absorbance profile is generally less complicated by accidental Fermi resonance. The IR frequencies of both probes undergo a substantial red shift upon going from water to aprotic solvents such as THF or DMSO. DFT calculations supported the hypothesis that the molecular origin of the higher observed frequency in water is primarily due to hydrogen bonds between the probes and water molecules.