Search

Black phosphorus (BP) is a narrow bandgap (∼0.3 eV) semiconductor with a great potential for optoelectronic devices in the mid-infrared wavelength. However, it has been challenging to achieve a high-quality scalable BP thin film. Here we present the successful synthesis of optically active BP films on a centimeter scale. We utilize the pulsed laser deposition of amorphous red phosphorus, another allotrope of phosphorus, followed by a high-pressure treatment at ∼8 GPa to induce a phase conversion into BP crystals. The crystalline quality was improved through thermal annealing, resulting in the observation of photoluminescence emission at mid-infrared wavelengths. We demonstrate high-pressure conversion on a centimeter scale with a continuous film with a thickness of ∼18 nm using a flat-belt-type high-pressure apparatus. This synthesis procedure presents a promising route to obtain optical-quality BP films, enabling the exploration of integrated optoelectronic device applications such as light-emitting devices and mid-infrared cameras on a chip scale.

Although amino acids are insensitive to visible light, as is generally accepted, we show that particular light-matter interaction can break this obviousness. Using sensitive (FT-IR)-technique in a combination of a broadband visible light source, we registered emission spectra of glycine in the range 2500-500 cm -1 . Sensitivity of the infrared emission spectrum to the exciting power -induced changes in the glycine structure was demonstrated experimentally.Vibrational spectra of glycine displayed the prominent spectral features of CH 2 , COO-, COOH, NH + 3 groups in the "fingerprint region". Simultaneous appearance of ionised COO- and unionised COOH forms of glycine in solution at neutral pH clearly indicated that visible light induces the partial protonation of COO- groups; if so, visible light irradiation should lead to occurrence of dimers or dimeric hydrogen - bonded structures. Spectroscopic and microscopic evidence of visible light-mediated formation of aggregates and nucleus in aqueous solution was presented.Electronic absorption/emission spectra of glycine in aqueous solution were primarily characterized in the near ultraviolet-visible region (240-600 nm). Negligible absorption near 270 nm was observed for a 1.0 M solution and dramatically enhanced with its "aging". Moreover, an extension of the absorption edge into the region above 400 nm could be seen. Due to the visible light irradiation, we observed modification of electronic structure or occurrence of additional species causing changes in absorption of glycine amino acid. For "aged" solution, it was shown that excitation spectra corresponding to the different emission wavelengths were entirely different, at that each excitation-spectral band had a characteristic emission band.Communicated by Ramaswamy H. Sarma.

This paper demonstrates a broadband and wide-temperature-range thermal emitter with super-hydrophobicity based on an oxidized high-entropy film. The annealed (NiCuCrFeSi)O high-entropy film can serve as a mid-infrared emitter due to its three characteristics: (i) high blackbody-like emission in a broadband mid-infrared region from 2.5 to 20 μm; (ii) high emittance (more than 90%) in a wide temperature range from 300 to 1000 K; (iii) super-hydrophobicity with a high contact angle of 151° and low tilt angle of 5°. These characteristics originate from the recrystallization of the as-deposited film and formation of a cavernous structure with a plethora of nanoscale polyhedrons and holes after an annealing process, supported by the results of XRD and SEM/EDX. This work may provide new ideas for applications of thermal emitters operating at a substantially wide temperature range.

Bismuth-germanate glasses with low hydroxide content co-doped with Ho 3+ /Yb 3+ ions have been investigated in terms of structural and spectroscopic properties. To reduce OH⁻ ions content and improve transmittance value at the wavelength of 3.1 µm, the glass synthesis has been carried out in low vacuum conditions (45-65 mBar). The composition of the host glass based on heavy metal oxides affects the maximum phonon energy (hω max = 724 cm -1 ), which low value has a positive impact on the mid-infrared emission parameters. Emission band at the wavelength of 2.87 µm was observed in glass co-doped with mol% 0.25 Ho₂O₃/0.75 Yb₂O₃ under 980 nm high power laser diode wavelength excitation. Lifetime measurements of the Yb 3+ :²F 5/2 quantum level indicate efficient Yb 3+ → Ho 3+ energy transfer (η = 61%). The developed active bismuth-germanate glass was used as the core of optical fibre operating in the mid-infrared region.

Alloying of CdS and PbS could potentially provide an important semiconductor with a wide range of bandgaps, with bandedge emission from mid-infrared to visible green, for various optoelectronic applications. We investigate the possibility of CdPbS alloy formation in nanowire and nanobelt forms, especially the dependence of alloy composition on two different cooling routes. Our results show that rapid cooling immediately after the growth phase can lead to a high-quality uniform alloy with Cd composition larger than possible at thermal equilibrium and by natural cooling. On the contrary, unassisted natural cooling leads to the formation of axial or core-shell heterostructures, containing segments with pure CdS and CdPbS alloys with lower Cd content than through rapid cooling. Such heterostructures with green and mid-infrared emission provide simultaneous access to two widely separated wavelengths from a single monolithic structure and can be important for many applications. Our results can help identify strategies for growing nanostructures with uniform alloy of high Cd incorporation, core-shell structures with shell serving as a passivating or protecting layer, or interesting longitudinal heterostructures. Both various heterostructures and uniform alloys of these materials could be important for high-efficiency solar cells, novel detectors, and nanolasing in wide spectral ranges.