Search

We report first-principles calculations of cluster silica with and without interstitial Bi0 atom. The size and radial distance of “Si-O-Si” rings are considered to study the equilibrium position of interstitial Bi0 atom in Bi-doped silica optical fiber. Our results reveal that the interstitial Bi0 atom is most likely to stay around ~ 2 A from the center of 6-membered rings. By comparing the transition energy levels with Bi0 atomic spectral data, we find that the transition 2D3/2(1) → 4S3/2 of interstitial Bi0 atom leads to the NIR emission estimated as ~ 1265 nm in Bi-doped silica optical fiber. Our methods will be effective to confirm bismuth-active centers for different valence states of Bi atom.

Razdobreev et al. claim that the energy level diagrams discussed in our paper are absolutely inconsistent with the experimental data. We carefully studied the comment and concluded that the claims on our paper are largely invalid. We maintain that the proposed diagrams in our paper can explain the luminescence in the spectral range of 1.4–1.7 µm and the spectral region 1.15 µm. Our calculated results are reliable for non-defective silica fiber models.

Two phenoxazine derivatives 1 and 2 were synthesized and their photoluminescent properties were systematically investigated. These two compounds presented crystallization-induced emission (CIE) with polymorphism-dependent emission (PDE). Compound 1 presented two single crystal structures with maximum emission wavelengths of 540 nm and 560 nm, while compound 2 possessed three single crystal structures with maximum emission wavelengths of 516 nm, 547 nm, and 556 nm, respectively. Moreover, compound 1 showed reversible mechanochromic luminescence by grinding/heating or solvent fuming processes.

We present first-principles combined GW and Bethe-Salpeter equation on passivation effect between ODC(I) and H/F atoms. The injection of H or F atoms help to form the robust Si H or Si F bond which increase the optical band gap, erase the defect state of ODC(I) at 0.74 eV and improve radiation toughness. The reaction of ODC(I) defect with a H atom or F atoms is barrierless, the Si O length near the ODC(I) sites are all gradually getting shorter and bond energy are getting stronger. Coupled with the atomic structures and electro-optic properties, we found out that F is the better passivator.

F and Cl atoms are always brought by the process of wet etching for fused silica devices, which dramatically influence the performance of the devices. The adsorption characteristics of F and Cl atoms with two main fused silica surface defects (E', NBOHC) were investigated on the basis of first-principle methods. Through the comparison of absorption capacity of different surface defects, we found that E' has larger capability to adsorb halogen atoms than NBOHC, and F atom is easier to be trapped by surface defects than Cl atom. Furthermore, the electronic structure and the bonding nature for surface defects are also studied and the calculations show that the introduction of F and Cl atoms will lead to the disappearing of defect states in band gap. And this adsorption process of F and Cl atoms on fused silica surface can be considered to chemical adsorption.

Monovalent bismuth-related centers in pure silica optical fiber are calculated by using first-principle methods. Transition energy levels of three different structural models are investigated on the basis of the time-dependent density functional theory (TDDFT). Compared with the experimental data of near-IR luminescence, our calculated results suggested that luminescence near 1492 nm is likely caused by SiOBi configuration; and luminescence at 1147 nm and 1403 nm may be caused by interstitial Bi2O molecule. Moreover, SiBi configuration, which might be the origin of the luminescence near 1629 nm, is difficult to directly form because of its relatively high formation energy.

Hydrogen peroxide (H2O2) has been associated as the most important member of reactive oxygen species (ROS) for a long time. Two novel fluorescent probes (P1 and P2) are synthesized and characterized for rapid detection of H2O2. In the presence of base, the probes provide remarkable changes in optical properties with extremely fast response towards H2O2 based on the cleavage of C O bond and the principle of excited state intramolecular proton transfer (ESIPT) or photo-induced electron transfer (PET).

Ground measured component radiative temperatures are basic inputs for modelling energy and hydrological processes and for simulating land surface temperature (LST) as “viewed” by remote sensors. However, knowledge of factors affecting the component temperatures and about their potential for upscaling LST over sparsely vegetated surfaces with high heterogeneity is still lacking. Here, a MUlti-Scale Observation Experiment on land Surface temperature (MUSOES) was performed under HiWATER over an arid sparsely vegetated surface. Component temperatures were obtained with different instruments on multiple spatial scales; for LST upscaling, a three-dimensional scene model was employed for two forest stations (MFS and PFS) and a two-dimensional model for a shrub station (SUP). Results show that intrinsic characteristics contribute to the temperature variability between different components and even within a single component. Using a thermal infrared (TIR) imager at MFS, average temperature difference of 24.9 K between sunlit bare soil and tree canopy was found; different components exhibit different internal temperature differences at direction-level and pixel-level. Furthermore, illumination conditions, viewing directions, and instrument types significantly affected the measured component temperatures. The measurements of the TIR radiometer and the imager can deviate considerably (e.g. 14.9 K for sunlit bare soil at MFS). When the longwave radiometers were selected as target sensors, the component temperatures measured by the imager exhibit good potential for LST upscaling: the upscaled LST has MBD/RMSD values of 2.0 K/2.3 K at MFS and 2.0 K/2.5 K at PFS. The TIR radiometer’s measurements introduce large uncertainties into LST upscaling at MFS and PFS, but result in good accuracy at SUP, mainly due to its simpler land cover and surface structure. Findings from this study can benefit our understanding of factors affecting observations of component temperatures and the LST upscaling process and are, therefore, relevant for further studying the evaluation of satellite LST products.