Fine-Tuned Visible and Near-Infrared Luminescence on Self-Assembled Lanthanide-Organic Tetrahedral Cages with Triazole-Based Chelates.

The construction of well-defined lanthanide complexes emitting in both the visible and near-infrared regions is of great importance due to their widespread applications in phosphors, light-emitting diodes, biosensors/probes, optical communications, etc. In comparison to the well-known mononuclear and dinuclear lanthanide complexes, multinuclear lanthanide supramolecular edifices with bright luminescence are still scarce. Herein, we report the coordination self-assembly of strongly luminescent lanthanide-organic tetrahedral Ln4L4 cages with a series of tris(tridentate) ligands based on the triazole chelates. Among them, the new ligand L3 with triazole-pyridine-triazole (TPT) chelates manifests an excellent sensitization toward all of the lanthanide ions (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) that emit in both the visible and near-infrared regions, with a record luminescent quantum yield for Tb4(L3)4 (Φ = 82%) being obtained. In contrast, ligands with amido-pyridine-triazole (APT) or TPA chelates show much weaker sensitization ability. Energy levels for all ligands were measured, and TD-DFT calculations were employed to shed light on the sensitization mechanism. Finally, white-light emission systems formed by combining the desired luminescent compounds have been demonstrated. Our strongly luminescent LOPs provide new candidates for photochemical supramolecular devices.

In situ study of hydrogenation of graphene and new phases of localization between metal-insulator transitions.

Monolayer graphene synthesized by chemical vapor deposition was subjected to controlled and sequential hydrogenation using RF plasma while monitoring its electrical properties in situ. Low-temperature transport properties, namely, electrical resistance (R), thermopower (S), Hall mobility (µ), and magnetoresistance (MR), were measured for each sample and correlated with ex situ Raman scattering and X-ray photoemission (XPS) characteristics. For weak hydrogenation, the transport is seen to be governed by electron diffusion, and low-temperature transport properties show metallic behavior (conductance G remains nonzero as T → 0). For strong hydrogenation, the transport is found to be describable by variable range hopping (VRH) and the low T conductance shows insulating behavior (G → 0 as T → 0). Weak localization (WL) behavior is seen with a negative MR for weakly hydrogenated graphene, and these WL effects are seen to diminish as the hydrogenation progresses. A clear transition to strong localization (SL) is evident with the emergence of pronounced negative MR for strongly hydrogenated graphene.

Psychometric Properties of the Chinese Version of the Primary Care Post-Traumatic Stress Disorder Screen-5 for Medical Staff Exposed to the COVID-19 Pandemic.

PURPOSE: The COVID-19 pandemic may increase the development of psychiatric disorders, such as posttraumatic stress disorder (PTSD) among medical staff. A brief validated screening tool is essential for the early diagnosis of PTSD. The purpose of the present study was to evaluate the validation of a Chinese version of the Primary Care-PTSD-5 (C-PC-PTSD-5) and determine an appropriate cutoff score with optimal sensitivity and specificity for medical staff in China during the COVID-19 pandemic. PARTICIPANTS AND METHODS: An online cross-sectional survey was conducted on medical staff (n = 1104) from 17 medical institutions in Shanghai. Questionnaires comprising general information, medical-related traumatic event experiences, the PTSD Checklist (PCL-5), and C-PC-PTSD-5 were distributed to participants using the online Questionnaire Star electronic system. Internal consistency, convergent validity, and test-retest reliability were calculated. Receiver operating characteristic (ROC) analysis was performed to determine diagnostic accuracy and the optimal cutoff score of the C-PC-PTSD-5 for medical staff. RESULTS: We included 1062 valid questionnaires for the analysis. Data of 838 traumatic experiences were analyzed. Internal consistency of the C-PC-PTSD-5 was satisfied (Cronbach's α = 0.756). The total score of the C-PC-PTSD-5 showed good test-retest reliability (r = 0.746). We found a strong correlation between the C-PC-PTSD-5 score and PCL-5 total score (r = 0.669, p < 0.001), which indicated good convergent validity. The ROC analysis showed an area under the curve of 0.81 ± 0.016. A cutoff score of 2 provided optimal sensitivity and specificity for the C-PC-PTSD-5 (sensitivity = 0.632, specificity = 0.871, Youden index = 0.503, and overall efficiency = 0.768). CONCLUSION: Our results indicated that the C-PC-PTSD-5 can be employed as a brief and efficient screening instrument for medical staff exposed to the COVID-19 pandemic. A score of 2 was identified as the optimal threshold for probable clinical PTSD symptoms.

Electrostatic deposition of graphene in a gaseous environment: a deterministic route for synthesizing rolled graphenes?

The synthesis of single-wall carbon nanotubes of desired diameters and chiralities is critical to the design of nanoscale electronic devices with desired properties. The existing methods are based on self-assembly, therefore lacking control over the diameters and chiralities. The present work reports a direct route for rolling graphene. Specifically, we found that the electrostatic deposition of graphene yielded: (i) flat graphene layers under high vacuum (10(-7) Torr), (ii) completely scrolled graphene under hydrogen atmosphere, (iii) partially scrolled graphene under nitrogen atmosphere, and (iv) no scrolling for helium atmospheres. Our study shows that the application of the electrostatic field facilitates the rolling of graphene sheets exposed to appropriate gases and allows the rolling of any size of graphene. The technique proposed here, in conjunction with a technique that produces graphene nanoribbons of uniform widths, will have significant impact on the development of carbon nanotube based devices. Furthermore, the present technique may be applied to obtain tubes/scrolls of other layered materials.

Three viologen-derived Zn-organic materials: photochromism, photomodulated fluorescence, and inkless and erasable prints.

Three zinc-viologen compounds, namely, {[Zn(Mebpy)(Hbtc)Cl]·2H2O}n (1), {[Zn3(Cebpy)2(Hbtc) (H2btc)2 (OH)2]·4H2O}n (2), and {[Zn4(Cebpy)2(IPA)3(OH)2]·2H2O}n (3) (Mebpy = N-methyl-4,4'-bipyridinium, Cebpy = N-carboxyethyl-4,4'-bipyridinium, H3btc = 1,3,5-benzenetricarboxylic acid, and H2IPA = isophthalic acid) have been constructed from aromatic carboxylic acid and viologen-derived ligands. In compound 1, the Hbtc2- ligands bridge Zn2+ cations to form a 1D fence-like chain with the Mebpy+ ligand suspended on the chains. Compound 2 possesses a 2D (4, 4) double-layered grid structure based on linear trinuclear Zn3O2 cluster units. The structure of compound 3 can be described as a 3D open-framework based on tetranuclear Zn4O2 cluster units and helical chains with helical channels. All three compounds display photochromic properties from pale yellow to dark blue after being irradiated by a xenon lamp with different photoresponsive rates. Compounds 2 and 3 can be deposited in paper simply by coating them with a solution of ethanol. The papers can be used as inkless and erasable print media. In addition, the photo-modulated luminescence of these compounds was also investigated.

Octahedron-shaped three-shell Ln14-substituted polyoxotungstogermanates encapsulating a W4O15 cluster: luminescence and frequency dependent magnetic properties.

A series of new Ln14-substituted polyoxometalates, H27Na16[(Ln14(H2O)W4(OH)O14)(WO4)4(GeW10O38)6]·nH2O (n ≈ 86) (1-Ln, Ln = Eu, Gd, Tb, Dy, Ho, Er), which contain 14 Ln3+ and 6 {α(1,5)-[GeW10O38]12-} units, has been synthesized in one-pot reactions. As the first 14-Ln-containing polyoxometalates, the octahedron-shaped three-shell structure of the [(Ln14(H2O)W4(OH)O14)(WO4)4(GeW10O38)6]43- polyanion is made up of a W4 tetrahedron, a Ln14W4 tetrahedron and a Ge6W60 octahedron. Compound 1-Dy exhibits frequency dependent magnetic properties. Compounds 1-Eu, 1-Tb and 1-Dy exhibit the characteristic emission bands of the Ln3+ ion.