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Attaching AIE-active L1 ([1,1':2',1'':4'',1'''-quaterphenyl]-2-yldiphenylphosphane) to AuCl, shortened the distances of P-C bonds to promote electron cloud overlap between Au I and L1 , affords 1 ( L1 AuCl) with aggregation-induced phosphorescence enhancement (AIPE) activity by 3 LMCT transitions. Then substituting the coplanar L2 (9-ethynylanthracene) for the Cl - in 1 providing 2 , switches the luminescence to aggregation-caused quenching (ACQ) activity. Furthermore, we restore the performance from ACQ to AIPE by metathesis reactions to transfer 2 into 1 . It is versatile synthetic strategy of reversible transformation between 1 and 2 that switches the luminescence of organogold(I) between AIPE and ACQ through balancing auxiliary ligands around the given metal.

The mechanical properties of carbon fiber (CF) reinforced composites are greatly dependent on the interfacial adhesion between fiber and resin matrix. Introducing nanoscale reinforcements into the interface is an effective approach to improve the interfacial adhesion of CF composites. In this paper, we proposed a facile and effective method for assembling poly(cyclotriphosphazene-co-4,4′-sulfonyldiphonel) nanotube onto CF surface as a novel multi-scale hybrid reinforcement through in situ template polymerization. The effects of surface modification on the surface and interface properties of CF and the resulting composite were investigated. After modification, the interfacial shear strength of fiber reinforced epoxy composites showed an increase of 26.4%. The reinforcing mechanisms were also analyzed, and the improvements on interfacial properties should mainly be attributed to mechanical interlocking effect. In addition, the modification even improved the fiber tensile strength by 6.6–16.3%, rather than deteriorating it.

The existing valence state (Eu2+/Eu3+ and Tb3+/Tb4+) in Eu/Tb ions doped in SrAl2Si2O8 were investigated through experimental and theoretical method. Their photoluminescence properties indicated that parts of Eu3+ ions were reduced to Eu2+ in SrAl2Si2O8. Based on the bond energy method, the reduction process of the Eu3+→Eu2+ and the preferentially occupancy of Eu3+/Eu2+ in SrAl2Si2O8 samples have been discussed. The values of deviation of its bond energy were calculated when Eu ions located at different crystal sites. Theoretical results indicated that the Eu3+ and Eu2+ would preferentially occupy the Sr sites due to the smaller energy variation. In addition, the variation of bond energy of Eu3+( Δ E Eu 3 + - O 2 - Sr =11.367 kcal/mol) is close to Eu2+ ( Δ E Eu 2 + - O 2 - Sr = 15.112 kcal/mol), which indicated that the both of Eu2+ and Eu3+can stably exist in SrAl2Si2O8 host. When Eu, Tb ions are co-doped in SrAl2Si2O8, the photoluminescence shows that only the characteristic emission peaks of Eu2+ and Eu3+ can be found and the emission of Tb3+ disappeared. It is suggested that the Tb3+ is oxidized to Tb4+ and the Eu3+ is reduced to Eu2+. Compared with Eu ion, the variation of bond energy for Tb3+( Δ E Tb 3 + - O 2 - Sr =10.084 kcal/mol) is more closer to Tb4+ ( Δ E Tb 4 + - O 2 - Sr =9.628 kcal/mol), so in Tb3+, Eu3+ co-doped in SrAl2Si2O8, the Tb4+ ion has the highest priority to occupy the Sr sites, Tb3+ loses one electron to form the tetravalent Tb4+, and the excess electrons are transferred to the surrounding neighboring Eu3+ site, Eu3+ gets an electron and is reduced to Eu2+. The theoretical results are in accord with the experimental measurement.

Graphene oxide (GO) was grafted onto the surface of carbon fiber (CF) by two synthetic routes with hexamethylene diisocyanate (HDI) tripolymer as the coupling agent. The first one was to use HDI tripolymer to modify the surface of GO, named GO-NCO, and then graft GO-NCO onto the oxidized carbon fiber surface. The other route was to use HDI tripolymer to modify the oxidized carbon fiber surface, named CFO-NCO, and then graft GO onto the CFO-NCO surface. The chemical compositions of the CF surface were confirmed by infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS). The surface morphologies of CF after modification and debonding from matrix were examined by scanning electron microscopy (SEM). The interfacial shear strength (IFSS) of CF/PA6 composites was also investigated by microbond test. It is found that the interfacial properties of GO modified carbon fiber reinforced polyamide 6 (CF-g-GO/PA6) composites are better by using the first route. The IFSS of CF-g-GO/PA6 composites reaches 61.4 MPa, is an increase of 40.2% compared with that of unmodified CF/PA6 composites. Moreover, the interfacial enhancement mechanism was further analyzed in detail.

Eu-doped MAlSi2O6 (M = Li, Na, K, Rb, Cs) phosphors were synthesized by solid-state reaction in air. The crystal structure and optical properties of the phosphors were investigated by X-ray powder diffraction and photoluminescence. Their emission spectra are composed of some broad bands coming from the 5d-4f transition of Eu2+ and some sharp emission peaks coming from the f-f transitions of Eu3+. The co-existence of Eu3+ and Eu2+ cations is detected in MAlSi2O6:2%Eu, which shows that the unusual Eu3+→Eu2+ reduction process occurs in MAlSi2O6. The preferential occupancy of Eu3+ or Eu2+ in MAlSi2O6 can be calculated to be M+ sites by the bond-energy method. The deviation of the Eu3+–O2- bond energy is closed to that of the Eu2+–O2- bond energy, which means that Eu3+ and Eu2+ can coexist in air. The abnormal reduction of Eu3+ to Eu2+ can be explained by charge compensation model. The doped Eu3+ was induced to M+ and the vacancy (VM) may be formed. The vacancy(VM) acted as a donor of electrons, and the Eu M ∙ ∙ defect acted as an acceptor of electrons. The theoretical result is consistent with the experimental phenomenon.

Data presented in this article are related to the research article entitled O2−–V5+ charge transfer band, chemical bond parameters and R/O of Eu3+ doped Ca(VO3)2 and Ca3(VO4)2: A comparable study[ing Li, Yu Pan, Wenjun Wang, Zihao Wen, Xuanxi Leng, Qi Wang, Liqun Zhou, Haibing Xu, Qinghua Xia, Li Liu, Hongping Xian, Xiaoguang Liu]. The data present the fitting results of the broad excitation spectra of Ca(VO3)2:1%Eu and Ca3(VO4)2:1%Eu using the Gaussian model, the O/R values using the experimental PL emission results. The data compares the optimized cell parameters for Ca(VO3)2: 1%Eu and Ca3(VO4)2:1%Eu through the CASTEP geometry optimization with their initial cell parameters.

A bond-energy method is used to determine the site occupancy preference of Eu3+ or Eu2+ and further firstly extended to study the spontaneous reduction of Eu3+ doped CaAl2Si2O8 based on the bond valence model. The phosphor CaAl2Si2O8: Eu was synthesized under air condition. The co-existence of Eu3+ and Eu2+ cations was detected through photoluminescence measurement. The occupancy of Eu3+ or Eu2+ in CaAl2Si2O8 can be determined by comparing the deviation of its bond energy in different locations at Ca2+, Si4+ and Al3+ sites. Theoretical calculation result indicates that the Eu3+ and Eu2+ would preferentially occupy the smaller energy variation sites Ca4, which can be assigned to Eu4 site. The more important result is that the energy variation of Eu2+ at Eu4 sites is smaller than that of Eu3+ at the same sites, which indicates that Eu2+ is more stable than Eu3+ at Eu4 sites, so the spontaneous Eu3+→Eu2+ reduction can be found in the CaAl2Si2O8. The same bond energy method can be extended to explain the reason why the Sm3+ doped CaAl2Si2O8 can't be reduced into Sm2+ under reduction condition. The theoretical result is consistent with the experimental phenomenon. This should help us to have a further understanding of spontaneous Eu3+→Eu2+ reduction in the inorganic material.

The local crystal sites occupied by Eu3+ in Ca5(BO3)3F:1% Eu3+ phosphor were investigated experimentally and theoretically. Ca5(BO3)3F:1% Eu3+ was synthesized by high-temperature solid-state method in air. The crystal structure and optical properties of the phosphor were studied by X-ray powder diffraction and photoluminescence, respectively. Two different O2− → Eu3+ CT broad bands with the peaks at 266 and 283 nm in Ca5(BO3)3F:1% Eu3+ were detected, indicating the Eu3+ sites occupied Ca2 and Ca1, respectively. The different sharp f–f emission spectra under the excitation of 283 and 266 nm proved that there are two different local lattice environments around Eu3+ existing in Ca5(BO3)3F:1% Eu3+. Environmental factor he, the standard deviation of environmental factor (EFSD) and the bond energy were used to illustrate and explain the site occupancy mechanism of Eu3+ into the host lattice. By comparing the intensity ratios of 5D0 → 7F2 transition to the 5D0 → 7F1 transition, I(5D0/7F2)/I(5D0/7F1) of Eu3+ at Ca2 (7.381) was found to be 2.5 times stronger than that of Eu3+ at Ca1 site (2.933). was calculated to analyze the I(5D0/7F2)/I(5D0/7F1) value. On the basis of the bond valence model, a bond-energy method was used to study the occupancy of the Eu ion, which indicated that the preferential sites of Eu ion occupancy in the Ca5(BO3)3F are the Ca2 and Ca1 sites. All three theoretical calculation results are consistent with each other.

CaY1−xAl1+xO4:2%Eu (x = 0, 0.1, 0.2) phosphors have been synthesized via a solid-state reaction process. XRD patterns indicate that they are pure phase. The photoluminescence properties of the CaY1−xAl1+xO4:2%Eu phosphors exhibit both the blue emission of Eu2+ (4f65d1–4f7) and red-orange emission of Eu3+ (5D0–7F1,2,3,4) under UV light excitation, which showed that the Eu3+/2+ co-doping system was obtained by adjusting the Al/Y ratio. Eu3+ ions can be reduced to Eu2+ ions when the Al/Y ratio was changed. In this work, the bond energy method was used to determine and explain the mechanism of the site occupation of Eu ions entering the host matrix. Also, the emission spectrum showed an unusual comparable intensity 5D0–7F4 transition peak. The relative intensity of 5D0–7F2 and 5D0–7F4 can be stabilized by changing the relative proportions of Al3+ and Y3+. Furthermore, this was explained by the J–O theory.

The dependence of photoluminescence (PL) properties of Eu 3+ activated two typical vanadates Ca 3 (VO 4 ) 2 and Ca(VO 3 ) 2 on the crystal structure was discussed experimentally and theoretically. Compared with the broad PL excitation spectrum of Ca 3 (VO 4 ) 2 : Eu with the peak at 339 nm, a 61-nm redshift of Ca(VO 3 ) 2 : Eu (at 400 nm) can be found. Under the excitation of near-UV light, the PL spectra of Ca 3 (VO 4 ) 2 :Eu and Ca(VO 3 ) 2 :Eu dominate red emission at 624 and 615 nm due to the 5 D 0 → 7 F 2 transitions, respectively. By comparing their intensity ratios (R/O) of the 5 D 0 → 7 F 2 transition (red, its intensity is labeled using “R”) to the 5 D 0 → 7 F 1 transition (orange, its intensity is labeled using “O”), R/O of Ca 3 (VO 4 ) 2 :Eu is 10 times stronger than that of Ca(VO 3 ) 2: Eu, which can be well explained by the proposed calculation model. Based on the dielectric theory of complex crystal, the important chemical bonds such as the covalency and the polarizability of the O-V or O-Ca bond volume were calculated quantitatively. It was shown that their broad excitation spectra were not the charge transfer (CT) from O to Eu, but is the CT from O to V, which also can be further demonstrated by the optical properties and the density functional theory calculations. Only O-V1 CT energy can efficiently be transferred to the activator due to the strong covalency of V1-O1 bond (0.2583) in the V- O -Eu bond. When Eu 3+ ions occupy the Ca1, Ca2, Ca3, Ca4 and Ca5 sites of Ca 3 (VO 4 ) 2 , the CT energy from O to Eu (O-Eu CT) can be predicted to be 6.22 eV (199 nm), 5.55 eV (223 nm), 5.57 eV (222 nm), 4.31 eV (287 nm) and 3.62 eV (342 nm), respectively. The predicted O-Eu CT energy in the Ca(VO 3 ) 2 : Eu is 4.02 eV (296 nm). For Eu 3+ doped Ca 3 (VO 4 ) 2 sample, the strongest red emission mainly comes from the substitution of Eu 3+ to the Ca5 site through calculation of the distortion degree using the standard deviation of environmental factor of the individual bond (EFSD) σ ( h e i ) . The bandgap energies of Ca(VO 3 ) 2 , Ca(VO 3 ) 2 : Eu, Ca 3 (VO 4 ) 2 and Ca 3 (VO 4 ) 2 : Eu were also determined.

A series of CaF 2 :xEu 3+ (x = 0.01–0.05) phosphors were synthesized by coprecipitation and high temperature solid-state method. Three different F - -Eu 3+ charge transfer (CT) bands in CaF 2 :xEu 3+ (x = 0.01–0.05) were detected through the PL spectra. Three local crystal environments (deformed O h octahedron, C 3V , C 4V ) were proposed in Eu 3+ doped CaF 2 . The broad peak at 277 nm is F - → Eu 3+ CT peak, in which Eu 3+ ions located deformed O h octahedron sites, the broad peak at 312 nm is due to Eu 3+ ions situating at C 4v sites, also, Eu 3+ ions with C 3v sites can make the F - → Eu 3+ CT produce a 38-nm redshift to 315 nm. Density functional theory (DFT) was performed to calculate the energy band gap(Eg) according to the three models. The calculation results consist with the experiment. The excitation peaks can be tuned in the same host through changing the local structure of Eu 3+ .

Introducing nanoscale reinforcements into the interface between carbon fiber (CF) and resin is an effective approach to improve the interfacial adhesion of CF composites. In this paper, a facile one-pot polymerization process provides a rapid and efficient method for preparing polyphosphazene microspheres/CF hybrid reinforcement using hexachlorocyclotriphosphazene (HCCP) and bis(4-hydroxyphenyl) sulfone (BPS) as monomers. By the in situ polymerization modification, HCCP and BPS were successfully cross-linked and deposited on the CF surface. Scanning electron microscope and atomic force microscopy images show that poly(cyclotriphosphazene- co -4,4′-sulfonyldiphonel) microspheres were introduced onto the CF surfaces and the surface roughness of fibers is enhanced obviously. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm that the polymerization between HCCP and BPS has been successfully carried out. The surface modification can significantly increase the fiber roughness, polarity, wettability and surface energy, thus improving the interfacial shear strength of CF/epoxy composites. Meanwhile, the single fiber tensile strength of CF also shows an increase after modification.

Continuous glass fiber (GF)-reinforced polymerized cyclic butylene terephthalate (pCBT) composites were prepared via vacuum-assisted resin transfer molding using butyltin tris(2-ethylhexanoate) as the catalyst. The relationship between melt viscosity and polymerization time was examined in the ring-opening polymerization of CBT resin. The effects of polymerization conditions such as catalyst content and polymerization temperature on viscosity average molar mass ( Mv), crystallization, mechanical properties, and microstructure of GF/pCBT composites were also investigated in detail. It is found that both high molecular weight and high degree of crystallinity of resin matrix can lead to high mechanical properties of composites. The composites prepared with 0.5% catalyst at 190°C show the best mechanical properties with tensile strength of 549 MPa, flexural strength of 585.2 MPa, and interlaminar shear strength of 47.1 MPa. The scanning electron microscopy analysis also demonstrates that good interfacial adhesion exists between fiber and resin, which agrees very well with experimental results.

The cyclomatrix-type polyphosphazene is hypothesized to have potential as optical material due to the existing of transparent P=N ring skeleton. However, as an insoluble and infusible cross-linked polymer, cyclomatrix-type polyphosphazene is very difficult to be processed into film coatings. Herein, we reported a facile in situ template method to prepare cyclomatrix-type polyphosphazene optical film coating based on in situ polymerization between chlorocyclophosphazene and 4,4’-oxydianiline. A transparent coating with smooth surface and a translucent coating with uneven surface were successfully obtained by controlling reaction time. Their molecular structures, surface morphologies and topographies, cross-section morphologies, optical properties and preparation mechanisms were studied, respectively. As expected, the novel film coatings had good transmission in the visible region, especially the smooth transparent coating, which exhibited high transmittance (80 ∼ 90%). Moreover, the coatings unexpectedly exhibited UV-shielding capacity, especially the uneven translucent coating, which blocked the vast majority of UVA radiation (78.6%) and almost all of UVB radiation (99.8%). In addition, the possible preparation mechanisms of two coatings were also discussed. The primary stage of polymerization was dominated by a film-forming process based on template self-assembly, leading to smooth transparent film coating. As polymerization progress, many cyclomatrix-type polyphosphazene microspheres were produced by a forming-microsphere process and then deposited on the film surface, forming uneven translucent coating.

To improve the interfacial adhesion of carbon fiber reinforced polymer composites (CFRP), carbon fiber usually has to be carried out surface treatment under harsh conditions. However, enhancing the interfacial property is usually accompanied by deteriorating tensile strength of carbon fiber, due to some defects on fiber surfaces after surface modification. In this paper, a layer of amine-capped poly (cyclotriphosphazene- co -4,4′-oxydianiline) coating was introduced onto the carbon fiber surfaces by a facile in-situ polymerization under mild condition. The amines on polyphosphazene coating surface help to improve the surface wettability and activity of carbon fibers, significantly improving the interfacial shear strength of carbon fiber/epoxy composites by 70.5%. Besides the enhanced surface wettability, the chemical bonds also play a key role in such an interfacial enhancement. Moreover, the polyphosphazene sheath can heal the surface defects of fiber effectively, thus increasing the fiber tensile strength by more than 10.0%.