[Show abstract][Hide abstract]ABSTRACT: Microchannels have important scientific applications in many fields, because they enable precise control, manipulation, and analysis of fluid on a micrometer scale. Herein, we demonstrate an effective strategy for fabrication of microchannels, based on the space-selective phase separation in glass induced by a femtosecond laser. The proposed method shows its abilities in fabrication of three-dimensional microchannels with ∼5 mm length scale and a uniform cross section. Moreover, we also achieve the modulation of the morphology on the inner surface of microchannels by using objective lenses with various numerical-apertures. The physical mechanism of the phase separation and microstructure evolution is discussed. Our method provides new opportunities to fabricate microchannels with complex structures and multifunctional integration.
[Show abstract][Hide abstract]ABSTRACT: The crystallization of matter at interfaces has long been a significant issue in science and technology, but surface-directed crystallization with controlled kinetics remains a matter of challenge. Here, we demonstrate a conceptual novel mechanism to steer liquid–solid phase transformation at interfaces by tailoring the chemical and structural inhomogeneity of a glass substrate through self-limited nanocrystallization of the glassy phase. Importantly, this approach enables large-scale development of metastable crystallization products, such as nanowire membranes. The thorough studies of the intermediate stages of crystallization reveal a unique cooperative mechanism in which the intricate interplays between inherent nanoscale forces and unique heterogeneous surfaces contribute to the mesoscale structural transformation from isolated units to superstructures. We further show that the constructed superstructures offer unprecedented opportuntities for the development of functional membrane systems possessing the combination of robust trace-detection performance and molecular trapping function. These findings not only present clear technological implications, but also provide an improved understanding of the fundamental mechanisms of surface-induced geological and biological processes.
[Show abstract][Hide abstract]ABSTRACT: We present a novel “Top-down” strategy to design the long phosphorescent phosphors in the second biological transparency window via energy transfer. Inherence in this approach to material design involves an ingenious engineering for hybridizing the coordination networks of hosts, tailoring the topochemical configuration of dopants, and bridging a cascaded tunnel for transferring the persistent energy from traps, to sensitizers and then to acceptors. Another significance of this endeavour is to highlight a rational scheme for functionally important hosts and dopants, Cr/Nd co-doped Zn1−xCaxGa2O4 solid solutions. Such solid-solution is employed as an optimized host to take advantage of its characteristic trap site level to establish an electron reservoir and network parameters for the precipitation of activators Nd3+ and Cr3+. The results reveal that the strategy employed here has the great potential, as well as opens new opportunities for future new-wavelength, NIR phosphorescent phosphors fabrication with many potential multifunctional bio-imaging applications.
[Show abstract][Hide abstract]ABSTRACT: UV-blocking materials are increasingly important in a variety of applications such as biological shield, cultural relics preservation and radiation hardening of electronic devices. A paramount challenge is the search for approaches that can produce material candidates combing both high ultraviolet absorbing capacity and low activity. Here we introduce an effective self-limited nanocrystallization method for construction of transparent Ce-containing glass composite. The unique crystallization process allows the in situ precipitation of UV absorbing center spanning a wide range of activation temperature, benefiting from the capability of viscous glassy matrix for modulating O2- and F- migrations. Photocatalysis/catalysis and UV-shielding tests firmly demonstrated that the obtained glass composite possesses suppressed photocatalytic/catalytic activity and excellent UV-blocking performance for both organics and bioactive cells. Our results suggest an innovative approach for fabrication of robust UV absorber that should find practical applications in protection of living creatures or cultural relics, especially in the case of direct contact with organic molecules or living cells.
[Show abstract][Hide abstract]ABSTRACT: In contrast to well-known multiple and fixed upconversion (UC) emission bands from lanthanide (Ln3+) ions activated luminescent materials, room temperature wavelength-tunable single-band UC emissions are designed and demonstrated in Ln3+ ions/transition metal Yb3+/Mn2+ codoped fluoride perovskites ABF3 (A = K+, Rb+, and Cs+; B = Mg2+, Zn2+, and Cd2+). Upon 976 nm laser excitation, the perovskites ABF3:Yb3+, Mn2+ exhibit intense single band UC emission centered at 550–610 nm depending on the substitution of the A+ and / or the B2+ species in ABF3. Crystal structure and luminescent properties analysis show that the UC emission should originate from the transitions of super-exchange coupled Yb3+–Mn2+ pair. The Stokes and UC emission properties, UC luminescence decay behaviors, as well as temperature dependent UC emission properties of ABF3:Yb3+, Mn2+ are investigated and discussed in detail. The intense room (or high) temperature UC emission and ultralong UC decay lifetimes (≈25–45 ms) clearly reveal that the perovskites ABF3:Yb3+, Mn2+ can be potentially applied in the fields of time-resolved luminescence imaging, lighting, and solid state lasers.
[Show abstract][Hide abstract]ABSTRACT: Polymeric nanofibers containing gold nanorods (GNRs) are aligned in a uniform orientation through electrospinning. The dispersive and absorptive parts of the third-order optical nonlinear optical refractive index of the composite film measured by polarization dependent z-scan method are demonstrated to be anisotropically enhanced. Anisotropic optical response of the aligned GNRs and its connection with the ultrafast electron dynamics are discussed in light of the results of resonant femtosecond pump-probe experiments. The significant appearance of anisotropic nonlinear optical properties of ensembles of GNRs is attributed to the sensitive excitation of longitudinal surface plasmon resonance (LSPR) of highly aligned GNRs. For the macroscopic applications of ensembles of GNRs, such as passive mode-locking and all-optical switching, the experimental results demonstrate that the alignment of GNRs through electrospinning should be very high efficient, and economic.
Article · Jan 2016 · ACS Applied Materials & Interfaces
[Show abstract][Hide abstract]ABSTRACT: Nonlinear optical (NLO) effects originating from materials doped with rare-earth ions possess colossal potential for application in all-optical switches. However, among previous studies, Er3+ ion-doped glass ceramics (GCs) with remarkable NLO features have been investigated with respect to optical modulation applications by tailoring their nonlinear transmittance upon excitation at various near-infrared (NIR) wavelengths, which might prove to be a simple way of achieving "on-off" optical modulation in future all-optical switches. Here, we present the first observation of tailorable nonlinear transmittance in germanate oxyfluoride GCs containing Er3+: LaF3 nanocrystals, manipulated by excitation at 808, 980, and 1550 nm, which is consistent with the results from theoretical calculations and simulations. Furthermore, we conduct experimental investigation and analysis related to energy level transitions and dynamical evolution, indicating that these intriguing NLO features can be attributed to the differentiation between excited state absorption accompanied by up-conversion luminescence and stimulated emission processes during excitation at discrepant NIR wavelengths. Importantly, bidirectional optical switching for the "on-off" toggle effect has been successfully demonstrated by selectively tailoring the nonlinear transmittance of the single Er3+-doped GCs. This tailorable NLO behavior of Er3+-doped GCs, which is dependent on excitation at different NIR wavelengths, might provide a versatile strategy for the development of next-generation bidirectional all-optical switches.
Full-text Article · Jan 2016 · Journal of Materials Chemistry C
[Show abstract][Hide abstract]ABSTRACT: Bismuth-doped multicomponent optical fiber was fabricated by a melt-in-tube method. The fiber was prepared at drawing temperature where the clad was softened, while the fiber core glass was melted. The obtained fiber was characterized by electroprobe microanalyzer and X-ray diffraction. No obvious precipitation of crystals or bismuth metals was observed in the fiber. Excited by 808-nm laser, intense broadband near-infrared emission with full width at half maximum of about 325 nm was observed from the fiber. Consequently, this fiber is promising for broadband fiber amplification. The melt-in-tube method is generally applicable for fabricating bismuth-doped multicomponent optical fiber.
Article · Dec 2015 · Journal of the American Ceramic Society
[Show abstract][Hide abstract]ABSTRACT: Glass ceramic fibers containing Ni2+doped LiGa5O8 nanocrystals were fabricated by a melt-in-tube method and successive heat treatment. Fiber precursors were prepared by drawing at high temperature where fiber core glass was melted while fiber clad glass was softened. After heat treatment, LiGa5O8 nanocrystals were precipitated in the fiber core. Excited by 980 nm laser, efficient broadband near-infrared emission was observed in the glass ceramic fiber compared to that of precursor fiber. The melt-in-tube method can realize controllable crystallization and is suitable for fabrication of novel glass ceramic fibers. The Ni2+-doped glass ceramic fiber is promising for broadband optical amplification.
[Show abstract][Hide abstract]ABSTRACT: Here, we demonstrate the relationship between glass network topological structure and the chemical state of embedded lanthanide ions. It is revealed that a more dispersed state of lanthanide ions is shown in more constrained 3D rigid network, which delivers valuable information toward homogeneous doping in glasses from the perspective of glass topological structure. The results are believed to be of great significances in the development of advanced optoelectronic devices like high-power laser, efficient fiber amplifier, smaller integrated photonic circuit, etc.
Full-text Article · Aug 2015 · Journal of the American Ceramic Society
[Show abstract][Hide abstract]ABSTRACT: A deep-ultraviolet (UV) nonlinear optical BaAlBO3F2 crystal was space-selective precipitated in stoichiometric 50BaF2-25Al2O3-25B2O3 glass by using a 500 kHz femtosecond pulse laser, which was confirmed by X-ray diffraction analysis (XRD). The distribution of BaAlBO3F2 crystals in glass was analyzed by Raman spectra and Raman mapping. The second-harmonic generation (SHG) intensity of BaAlBO3F2 crystals in glass could be tuned by changing the laser average power and exposure time. Absorption spectra were used to investigate the transmittance of the glass sample before and after the femtosecond laser irradiation.
Article · Jul 2015 · Journal of Non-Crystalline Solids
[Show abstract][Hide abstract]ABSTRACT: Glass-ceramic fibers containing Cr3+-doped ZnAl2O4 nanocrystals were fabricated by the melt-in-tube method and successive heat treatment. The obtained fibers were characterized by electro-probe micro-analyzer, X-ray diffraction, Raman spectrum and high-resolution transmission electron microscopy. In our process, fibers were precursor at the drawing temperature where the fiber core glass was melted while the clad was softened. No obvious element interdiffusion between the core and the clad section or crystallization was observed in precursor fiber. After heat treatment, ZnAl2O4 nanocrystals with diameters ranging from 1.0 to 6.3 nm were precipitated in the fiber core. In comparison to precursor fiber, the glass-ceramic fiber exhibits broadband emission from Cr3+ when excited at 532 nm, making Cr3+-doped glass-ceramic fiber a promising material for broadband tunable fiber laser. Furthermore, the melt-in-tube method demonstrated here may open a new gate toward the fabrication of novel glass-ceramic fibers.
Article · Jun 2015 · Journal of the American Ceramic Society
[Show abstract][Hide abstract]ABSTRACT: We present a series of efficient near-infrared (NIR) Cr3+-doped non-gallate long-persistence phosphors (Zn2SnO4: Cr and Zn(2-x)Al2xSn(1-x)O4: Cr) and highlight their special optical characteristics of broad emission band (650-1200 nm, peaking at 800 nm) and long afterglow duration (>35h). In the context of materials selection, these systems successfully avoid the existing ubiquitous reliance on gallates as hosts in Cr3+-doped phosphorescent phosphors. Zn2SnO4 is employed as a host to take advantage of its characteristic inverse spinel crystal structure, easy substitution into Zn2+ and Sn4+ sites by Cr3+ in distorted octahedral coordination and non-equivalent substitution. In this work, Al dopant was introduced both to precisely tailor the local crystal field around the activator center, Cr3+, and to redeploy trap distribution in the system. Indeed, such redeployment permits band gap adjustment and the dynamic variation of the annihilation and the formation of defects. The results demonstrate that the method employed here can be an effective way to fabricate multi-wavelength, low-cost, NIR phosphorescent phosphors with many potential multifunctional bio-imaging applications.
[Show abstract][Hide abstract]ABSTRACT: We present a series of efficient near-infrared (NIR) Cr3+-doped non-gallate long-persistence phosphors (Zn2SnO4: Cr and Zn(2-x)Al2xSn(1-x)O4: Cr) and highlight their special optical characteristics of broad emission band (650-1200 nm, peaking at 800 nm) and long afterglow duration (>35 h). In the context of materials selection, these systems successfully avoid the existing ubiquitous reliance on gallates as hosts in Cr3+-doped phosphorescent phosphors. Zn2SnO4 is employed as a host to take advantage of its characteristic inverse spinel crystal structure, easy substitution into Zn2+ and Sn4+ sites by Cr3+ in distorted octahedral coordination and non-equivalent substitution. In this work, Al dopant was introduced both to precisely tailor the local crystal field around the activator center, Cr3+, and to redeploy trap distribution in the system. Indeed, such redeployment permits band gap adjustment and the dynamic variation of the annihilation and the formation of defects. The results demonstrate that the method employed here can be an effective way to fabricate multi-wavelength, low-cost, NIR phosphorescent phosphors with many potential multifunctional bio-imaging applications.
[Show abstract][Hide abstract]ABSTRACT: Construction of chip-based optical microcavity from multi-component glass has long been a significant fundamental challenge in the cross field of materials science and photonics. Here we introduced a scalable non-hydrolytic sol-gel method for deposition of multi-component glass film with high thickness and superior homogeneity. Prototypically, we demonstrated the success in fabrication of multi-component tellurite thick film, and construction of tellurite microcavity on silicon chip through a combined etching technology for the first time. The collaborative studies by using steady-state spectrum, whisper gallery mode (WGM) resonance spectrum and electric field distribution firmly indicate that the obtained thick film and microcavity present excellent properties, point to the promising application in integrated photonics.
[Show abstract][Hide abstract]ABSTRACT: It has been observed that BaCl2:Er3+ phosphors have a higher up-conversion luminescence efficiency than the well-known fluoride regarded widely as the most efficient up-conversion host material. The near-infrared-to-visible up-conversion luminescence is markedly enhanced for BaCl2:Er3+ phosphors when excited simultaneously at two wavelengths (808 and 980 nm) in contrast to the case of single-wavelength excitation. Furthermore, our results demonstrate that the multiwavelength simultaneously excited up-conversion process in BaCl2:Er3+ phosphors allows better and broader harvesting of near-infrared solar energy, which is expected to open the possibilities of the remarkable improvement of the power conversion efficiency of next-generation solar cells.
Full-text Article · Mar 2015 · Applied Physics Express