Molecular Engineering Modulating the Singlet-Triplet Energy Splitting of Indolocarbazole-Based TADF Emitters Exhibiting AIE Properties for Nondoped Blue OLEDs with EQE of Nearly 20.

The development of efficient blue thermally activated delayed fluorescence (TADF) emitters with an aggregation-induced emission (AIE) nature, for the construction of organic light-emitting diodes (OLEDs), is still insufficient. This can be attributed to the challenges encountered in molecular design, including the inherent trade-off between radiative decay and reverse intersystem crossing (RISC), as well as small singlet-triplet energy splitting (ΔEST) and the requirement for high photoluminescence quantum yields (ΦPL). Herein, we present the design of three highly efficient blue TADF molecules with AIE characteristics by combining π-extended donors with different acceptors to modulate the differences in the electron-donating and electron-withdrawing abilities. This approach not only ensures high emission efficiency by suppressing close π-π stacking, weakening nonradiative relaxation, and enhancing radiative transition but also maintains the equilibrium ratio between the triplet and singlet excitons by facilitating the process of RISC. These emitters exhibit AIE and TADF properties, featuring quick radiative rates and low nonradiative rates. The ΦPL of these emitters reached an impressive 88%. Based on their excellent comprehensive performance, nondoped PICzPMO and PICzPMO OLEDs achieved excellent electroluminescence performance, exhibiting maximum external quantum efficiency (EQEmax) of up to 19.5%, while the doped device achieved a higher EQEmax of 20.8%. This work demonstrated that by fusing π-extended large rigid donors with different acceptors, it is possible to regulate the difference in electron-donating and electron-withdrawing abilities, resulting in a small ΔEST, high ΦPL, and fast RISC process, which is a highly feasible strategy for designing efficient TADF molecules.

Remarkably Enhanced Red Upconversion Emission in ß-NaLuF4:Er,Tm Microcrystals via Ion Exchange.

Internal OH- defects always cause significant depletion of excitation energy for low upconversion efficiency; however, preventing the incorporation of OH- into the crystal lattice is very difficult during the synthesis of upconversion crystals. In this work, red upconversion emission is dramatically enhanced in Er3+-sensitized hexagonal NaLuF4 (ß-NaLuF4) microcrystals through a collaborative effect of ion exchange and Tm3+ doping. The ion exchange can not only maintain the morphology very well but also strongly reduce the internal OH- defects, which can enhance the upconversion luminescence due to improved excitation energy harvesting and red to green (R/G) ratio due to intense cross-relaxation. Doping of Tm3+ as an energy trapping center not only regulates the red emission output but also reduces the excitation energy loss. ß-NaLuF4:Er,Tm microcrystals after ion exchange exhibit stronger red upconversion emission compared with ß-NaYF4:Er,Tm and ß-NaGdF4:Er,Tm counterparts. Moreover, fluorescent labeling of the fingerprint pattern printed from ß-NaLuF4:Er,Tm microcrystals with stable and intense red fluorescence has been demonstrated under 980 nm excitation.

Exploring the Effects of Argument Map-Supported Online Group Debate Activities on College Students' Critical Thinking.

Debate has been warranted as a meaningful activity to promote students' higher-level thinking, such as critical thinking. However, traditional debate activities which are typically carried out in the physical classroom may meet some obstructions of limited time and space, which would result in the phenomenon that many participants act as silent watchers rather than mind exchangers. Moreover, it is hard to make a visualized record about the whole process and contents of the traditional debate activity. The current study aimed to explore the effects of argument map (AM)-supported online group debate activities on college students' critical thinking, including their depth and phases of critical thinking, and the relationship between students' depth of critical thinking and their number of speeches. In the study, an innovative argumentation construction way was designed. All students enrolled in a course could have a chance to attend the AM-supported online group debate activities and the whole process and outcomes of online group debate could be visualized by AM. At the same time, the effectiveness of the innovative activities was evaluated by content analysis of AM. A total of 42 sophomores in the undergraduate course named "Learning Sciences and Technology" were recruited to attend online group debate activities assisted by a web-based visualization tool named "ZJU Yuque" in 5 weeks. Newman's framework about the depth of critical thinking and Murthy's instrument of critical thinking phases were employed as guidelines. We found that 42 students' overall depth of critical thinking was gradually improved in an obvious way during the five online debate activities. The most frequent phases for students in the first and second team in online group debate activities include Understand→Understand (U→U), Recognize→Understand (R→U), and Understand→Evaluate (U→E). However, students' creating behaviors were not significantly generated. Teachers' real-time feedback was helpful for students' improvements of high-level thinking skills and their preparation for the next debate activity. Students' interviews found that students highly valued such online group debate activities because every student could have a chance to express their thoughts and they had enough time to prepare debate contents. Based on the findings, some implications were proposed for the better design and implementation of online group debate activities.

Investigating the Influence of Tacit Knowledge Transformation Approach on Students' Learning Ability.

Tacit knowledge is an essential foundation for developing students' learning ability, especially in understanding and solving problems. However, the transforming of tacit knowledge confront a big challenge during the outbreak of Corona Virus Disease 2019 (COVID-19), because most teaching and learning activities were conducted in online context, which impair a face-to-face interaction. To explore the effect of tacit knowledge on students' learning ability in the online learning environments, the current study based on SECI model (The Socialization, Externalization, Combination, and Internalization) proposed to design the tacit knowledge transformation teaching approach. To assess the effectiveness of this approach, 60 elementary school students were recruited in the quasi-experiment. The results of retention test and transfer test showed that the experimental group, using the tacit knowledge transformation teaching approach, has significant improvement on learning ability than the control group. The current research theoretically provide a teaching strategy on tactic knowledge, and practically helps teachers to organize instructional activities, thereby, advocating the appropriate use of social media.

Effect of Gig Workers' Psychological Contract Fulfillment on Their Task Performance in a Sharing Economy-A Perspective from the Mediation of Organizational Identification and the Moderation of Length of Service.

Workers' isolation may occur in gig employment in the sharing economy, which generates a weak perception of the organization and unpredictable work performance. Drawing on social exchange theory, this paper proposes a framework to explore the effect of psychological contract fulfillment on gig workers' task performance from the perspective of the mediation of organizational identification and the moderation of the length of service. A total of 223 samples were recruited from Didi (a ride-hailing company in China) drivers. The results show that both transactional and relational psychological contract fulfillment can directly affect gig workers' task performance and also indirectly affect it via organizational identification. When the length of service for the current company is taken into consideration, transactional contract fulfillment, as the representation of a company's recognition of gig workers' effort, has a stronger effect on the organizational identification of gig workers who have been working for the company for less than a year compared with those who have been working for a longer period. The results show no difference in the relationship between relational psychological contract and organizational identification between the two groups. Transactional psychological contract fulfillment exhibits the same significant effect on gig workers' task performance in both groups. By contrast, relational psychological contract fulfillment has a stronger effect on long-serving Didi drivers than on those who joined the company within the year. These findings generate certain theoretical and practical implications for gig employment management in the sharing economy.

Tit for Tat: Abusive Supervision and Knowledge Hiding-The Role of Psychological Contract Breach and Psychological Ownership.

The extant literature has focused on individuals' knowledge-sharing behavior and its driving factors, which stimulate the knowledge transmission and exchange in organizations. However, little research has focused on factors that inhibit knowledge sharing and encourage individuals to hide their knowledge. Therefore, based on social exchange and displaced aggression theories, the study proposed and checked a model that examined the effect of abusive supervision on knowledge hiding (KH) via a psychological contract breach (PCB). The Psychological ownership was regarded as a boundary condition on abusive supervision and KH relationship. Using a time-lagged method, we recruited 344 full-time employees enrolled in an executive development program in a large university in China. The findings show that PCB mediates the association between abusive supervision and KH. Similarly, psychological ownership moderates the association between abusive supervision and KH. Employees with high psychological ownership minimized the effect of abusive supervision on KH. Based on study findings, contributions to theory and practice, limitations, and future directions are discussed.

Correlative Factors of the Deterioration of Necrotizing Enterocolitis in Small for Gestational Age Newborns.

Small for gestational age (SGA) infants have an increased risk of necrotizing enterocolitis (NEC), but SGA has been found to not be a risk factor for the deterioration of NEC in previous literature. Few studies have focused on correlative factors of the progression of NEC in SGA newborns. The present retrospective observational study was performed in 64 SGA infants with Bell's stage II NEC. The dependent variable was Bell's stage II NEC that progressed to stage III after diagnosis. A stepwise forward multivariate logistic regression model was used to select potential correlative factors for the progression of NEC in SGA newborns. The results showed that elevation of CRP after NEC diagnosis (aOR 39.21, 95% CI 6.62-249.2) has an increased risk for deteriorating Bell's stage II NEC. In contrast, NEC in infants with congenital heart disease had a decreased risk of deterioration (aOR 0.11, 95% CI 0.01-0.92). Our findings indicated that serial CRP measurements post NEC diagnosis may be useful in predicting the deterioration of NEC.

Construction of p66Shc gene interfering lentivirus vectors and its effects on alveolar epithelial cells apoptosis induced by hyperoxia.

BACKGROUND: The aim of this study is to observe the inhibitive effects of p66Shc gene interfering lentivirus vectors on the expression of p66Shc, and to explore its effects on alveolar epithelial cells apoptosis induced by hyperoxia. METHODS: The gene sequences were cloned into the pLenR-GPH-shRNA lentiviral vector, which was selected by Genebank searches. The pLenR-GPH-shRNA and lentiviral vector packaging plasmid mix were cotransfected into 293T cells to package lentiviral particles. Culture virus supernatant was harvested, and then the virus titer was determined by serial dilution assay. A549 cells were transduced with the constructed lentiviral vectors, and real-time polymerase chain reaction (RT-PCR) and Western blot were used to evaluate p66Shc expression. This study is divided into a control group, a hyperoxia group, an A549-p66ShcshRNA hyperoxia group, and a negative lentivirus group. Cell apoptosis was detected by flow cytometry after 24 hours; the expression of X-linked inhibitor of apoptosis protein (XIAP) and caspase-9 were detected by immunohistochemistry assay. The production of reactive oxygen species and cellular mitochondria membrane potential (ΔΨm) were determined by fluorescence microscopy. RESULTS: We successfully established the p66Shc gene interfering lentivirus vectors, A549-p66ShcshRNA. The A549-p66ShcshRNA was transfected into alveolar epithelial cells, and the inhibitive effects on the expression of p66Shc were observed. Both RT-PCR and Western blot demonstrated downregulation of p66Shc expression in A549 cells. In the A549-p66ShcshRNA hyperoxia group, we found dampened oxidative stress. A549-p66ShcshRNA can cause p66Shc gene silencing, reduce mitochondrial reactive oxygen species generation, reduce membrane potential decrease, reduce the apoptosis of A549 cells, and reduce alveolar epithelial cell injury, while the lentiviral empty vector group had no such changes. CONCLUSION: p66Shc gene interfering lentivirus vector can affect the alveolar epithelial cells apoptosis induced by hyperoxia.

[Diphenylene iodonium and apocynin reduce the translocation and level of p47phox in PBMCs of premature infants to inhibit reactive oxygen species production].

OBJECTIVE: To observe the effects of NADPH oxidase inhibitor diphenylene iodonium (DPI) and apocynin on the generation of reactive oxygen species (ROS) induced by p47phox and the mechanism of p47phox-induced ROS production under hyperoxic conditions. METHODS: Peripheral blood mononuclear cells (PBMCs) were isolated from the peripheral blood (2 mL) of premature infants of less than 32 weeks without oxygen uptake. The isolated cells were divided into four groups, control group, hyperoxia group, hyperoxia and DPI group, hyperoxia and apocynin group. The control group was cultured in incubator with 50 mL/L CO(2) at 37°, and the other groups were cultured in 950 mL/L O(2) and 50 mL/L CO(2) mixed gas. After 48 hours, ROS was detected by Mitosox Red staining under a confocal laser scanning microscope; malondialdehyde (MDA) was measured by thiobarbituric acid colorimetry; the location and translocation rate of p47phox was observed by immunofluorescence staining; the level of p47phox protein was tested by Western blotting. RESULTS: Compared with the hyperoxia group, the remaining three groups showed significantly decreased ROS and MDA levels and reduced translocation rate and level of p47phox. Compared with the control group, both the hyperoxia and DPI group and the hyperoxia and apocynin group were not significantly different in the above indexes. CONCLUSION: DPI and apocynin can reduce hyperoxia-induced ROS production by decreasing the translocation and level of p47phox.

[Resveratrol increases sirtuin 1 expression in peripheral blood mononuclear cells of premature infants and inhibits the oxidative stress induced by hyperoxia in vivo].

OBJECTIVE: To explore the effect of resveratrol on the levels of sirtuin 1 (SIRT1) and reactive oxygen species (ROS) in peripheral blood mononuclear cells (PBMCs) of premature infants exposed to hyperoxia. METHODS: Peripheral blood and isolated PBMCs from premature infants (gestational age<32 weeks) without oxygen supplement were collected and were randomly assigned into four groups: control, air+resveratrol, hyperoxia, and hyperoxia+resveratrol. The PBMCs were cultured in vitro for 48 hours, then the ROS content in PBMCs was measured by laser scanning confocal microscopy. Malondialdehyde (MDA) content in the medium was measured by the whole spectrum spectrophotometer. SIRT1 positioning was assessed by immunofluorescence. SIRT1 expression levels in PBMCs were measured by Western bolt. RESULTS: Compared with the control group, the level of SIRT1 in the air+resveratrol group increased significantly (P<0.05). The levels of ROS and MDA and the SIRT1 transposition rate in the hyperoxia group increased significantly, while the expression level of SIRT1 decreased significantly compared with the control group (P<0.05). The levels of ROS and MDA and the SIRT1 transposition rate decreased significantly (P<0.05), and the expression level of SIRT1 increased significantly in the hyperoxia+resveratrol group (P<0.05). CONCLUSIONS: Resveratrol can increase SIRT1 expression in PBMCs and inhibit SIRT1 shuttle from nucleus to cytoplasm in order to increase the ability of antioxidative stress in premature infants exposed to hyperoxia, thereby reducing the oxidative stress injury in premature infants.

Mechanism of p47phox-induced increase of reactive oxygen species in peripheral blood mononuclear cells from premature infants on oxygen therapy.

OBJECTIVE: This study aimed to explore the mechanism of p47phox-induced increase of reactive oxygen species (ROS) in peripheral blood mononuclear cells (PBMCs) from premature infants after oxygen therapy, and determine a new target for oxidative stress injury alleviation in clinical setting. METHODS: First, ROS levels as well as p47phox translocation and expression in PBMC samples were evaluated after treatment of premature infants with different concentrations of oxygen. Then, changes of all various parameters were detected after in vitro treatment of PBMCs with diphenyleneiodonium (DPI), apocynin, and high oxygen levels. RESULTS: In premature infants, ROS levels increased significantly after treatment with oxygen, in a concentration-dependent manner (p < 0.05); meanwhile, p47phox translocation and expression were significantly enhanced (p < 0.05) as well. In agreement, PBMCs cultured in vitro showed increased ROS levels after treatment with high oxygen concentrations; p47phox translocation, and expression increased as well (p < 0.05). However, treatment with DPI or apocynin resulted in opposite effects. CONCLUSION: Treatment with oxygen increases p47phox translocationand expression, which in turn induce ROS production. DPI and apocynin have the opposite effects.

[Hyperoxia induces reactive oxygen species production and promotes SIRT1 nucleocytoplasmic shuttling of peripheral blood mononuclear cells in premature infants in vitro].

OBJECTIVE: To explore the relationship between deacetylase sirtuin 1 (SIRT1) and reactive oxygen species (ROS) after oxygen therapy in the peripheral blood mononuclear cells (PBMCs) of the premature infants. METHODS: According to the fraction of inspired O2 (FiO2), premature infants diagnosed with respiratory distress syndrome (RDS) (gestational age <32 weeks), were divided into three groups: low dosage oxygen group (FiO2 <300 mL/L), moderate dosage oxygen group (FiO2; 300 mL/L-400 mL/L), high dosage oxygen group (FiO2 >400 mL/L). After 48 hours of oxygen treatment, PBMCs and serum were collected from the peripheral blood. Then the intracellular ROS level was detected by MitoSOX(TM) Red labeling combined with confocal laser scanning microscopy; the malondialdehyde (MDA) content in the serum was determined by the whole spectrum spectrophotometer; the SIRT1 localization was observed by immunofluorescence staining; and the SIRT1 levels in PBMCs were examined by Western blotting. RESULTS: With the increase of FiO2, the ROS, MDA content and the rate of SIRT1 nucleocytoplasmic shuttling of PBMCs gradually increased and SIRT1 protein expression was significantly lowered. CONCLUSION: Hyperoxia induces ROS production in premature infants, promotes SIRT1 to cross from nucleus to cytoplasm, inhibits the resistant ability of SIRT1 to oxidative stress.

Growth of lanthanide-doped LiGdF4 nanoparticles induced by LiLuF4 core as tri-modal imaging bioprobes.

Multimodal imaging can compensate for the deficiencies and incorporate the advantages of individual imaging modalities. In this paper, we demonstrated the synthesis of core-shell nanocomposites LiLuF4@LiGdF4:Yb,Er/Tm constituted of tetragonal LiLuF4 nanoparticles as core and Yb,Er/Tm-codoped LiGdF4 as shell. LiLuF4@LiGdF4:Yb,Er/Tm nanoparticles display brighter upconversion luminescence (UCL) than NaGdF4:Yb,Er/Tm nanoparticles with the same size under continuous-wave excitation at 980 nm. The active shell layer of LiGdF4:Yb,Er/Tm not only provide the UCL center, but also serve as magnetic resonance (MR) imaging contrast agent. To further improve the UCL intensity, the inert LiGdF4 shell was coated on the LiLuF4@LiGdF4:Yb,Er/Tm nanoparticles. Furthermore, LiLuF4@LiGdF4:Yb,Tm@LiGdF4 nanoparticles have been successfully applied to UCL/X-ray computed tomography (CT)/MR tri-modal imaging on the modal of tumor-bearing mice.

[Resveratrol inhibits hyperxia-induced cell apoptosis through up-regulating SIRT1 expression in HPAECs].

OBJECTIVE: To investigate the protection effect of sirtuin 1 (SIRT1) agonist resveratrol (Res) against the apoptosis of human pulmonary alveolar epithelial cells (HPAECs) induced by hyperxia. METHODS: The HPAECs in vitro were randomly divided into three groups: control group, hyperxia group, Res group. After 24-hour culture, the expressions of caspase-9, X-linked inhibitor of apoptosis protein (XIAP), SIRT1 proteins were measured by SP immunohistochemistry. The changes of reactive oxygen species (ROS) marked with MitoSOX(TM) and membrane potential marked with JC-1 in mitochondrion were detected by laser scanning confocal microscopy. The expression of SIRT1 protein was determined by Western blotting, and the change of cell apoptosis rate was analyzed by flow cytometry combined with annexin V-FITC/PI staining. RESULTS: Compared with the control group, the expression of caspase-9, the generation of ROS in mitochondrion of HPAECs and the cell apoptosis rate increased obviously. The expressions of both XIAP and SIRT1 and membrane potential decreased evidently in the hyperxia group. Compared with the hyperxia group, the expression of caspase-9, the generation of ROS in mitochondrion of HPAECs and the cell apoptosis rate went down obviously. The expressions of XIAP and SIRT1, and the membrane potential went up evidently in the Res group. CONCLUSION: By up-regulating the expression of SIRT1 in of HPAECs and depressing the generation of ROS, Res inhibits the apoptosis of HPAECs and maintains the cell membrane potential, thus effectively alleviating hyperxia-induced lung injury.

[Silencing of Pin1 suppresses hyperoxia-induced apoptosis of A549 cells].

OBJECTIVE: To explore the effect of silence of Pin1 expression on hyperoxia-induced apoptosis in alveolar epithelial cells A549. METHODS: A549 cells were divided into four groups: control, hyperoxia, negative lentivirus and Pin1-shRNA hyperoxia. The hyperoxia group was exposed to a mixture of 95%O2 and 5%CO2 for 10 minutes. Then cells were cultured in a closed environment. After 24 hours, the changes of morphology were observed under an inverted microscope. Cell apoptosis was detected by flow cytometry (FCM). The expression of X-linked inhibitor of apoptosis protein (XIAP) and Caspase-9 were detected by immunohistochemistry. The production of reactive oxygen species (ROS) and cellular mitochondria membrane potential (△Ψm) were determined by fluorescence microscopy. RESULTS: Under the inverted microscope, the A549 cells grew slowly and the changes in morphology of the cells were most obvious in the hyperoxia and negative lentivirus groups. The changes in morphology of A549 cells were obviously improved in the Pin1-shRNA hyperoxia group. The FCM results showed that the apoptosis rate of A549 cells increased, Caspase-9 expression increased, XIAP expression decreased, mitochondrial ROS production increased and mitochondrial membrane potential decreased in the hyperoxia and negative lentivirus groups compared with the control group (P<0.05). Compared with the hyperoxia and negative lentivirus groups, the apoptosis rate of A549 cells decreased, Caspase-9 expression decreased, XIAP expression increased, mitochondrial ROS production decreased and mitochondrial membrane potential increased in the Pin1-shRNA hyperoxia group (P<0.05), although the levels of the indexes did not reach to those of the control group. CONCLUSIONS: Silencing of Pin1 could suppress hyperoxia-induced apoptosis of A549 cells.

[Roles of PKCß/P66Shc oxidative stress signal pathway in mediating hyperoxia-induced ROS production in alveolar epithelial cells].

OBJECTIVE: To explore the roles of PKCß/P66Shc oxidative stress signal pathway in mediating hyperoxia-induced reactive oxgen species (ROS) production in alveolar epithelial cells (A549) and the protective effects of PKCß inhibitor on hyperoxia-induced injuries of alveolar epithelial cells. METHODS: A549 cells were cultured in vitro and randomly divided into three groups: control, hyperoxia and PKCß inhibitor LY333531 treatment. The hyperoxia group was exposed to a mixture of O2 (950 mL/L) and CO2 (50 mL/L) for 10 minutes and then cultured in a closed environment. The LY333531 group was treated with PKCß inhibitor LY333531 of 10 µmol/L for 24 hours before hyperoxia induction. Cells were collected 24 hours after culture and the levels of PKCß, Pin1, P66Shc and P66Shc-Ser36 were detected by Western blot. The intracellular translocation of P66Shc, the production of ROS and cellular mitochondria membrane potential were measured using the confocal microscopy. RESULTS: Compared with the control group, the levels of PKCß, Pin1, P66Shc and P-P66Shc-Ser36 in A549 cells 24 hours after culture increased significantly in the hyperoxia group. These changes in the hyperoxia group were accompanied with an increased translocation rate of P66Shc from cytoplasm into mitochondria, an increased production of mitochondrial ROS, and a reduced mitochondrial membrane potential. Compared with the hyperoxia group, the levels of Pin1, P66Shc and P66Shc-Ser36 in A549 cells, the translocation rate of P66Shc from cytoplasm into mitochondria and the production of mitochondrial ROS decreased significantly, while the mitochondrial membrane potential increased significantly in the LY333531 treatment group. However, there were significant differences in the above mentioned measurements between the LY333531 treatment and control groups. CONCLUSIONS: Hyperoxia can increase the expression of PKCß in alveolar epithelial cells and production of mitochondrial ROS and decrease mitochondrial membrane potential. PKCß inhibitor LY333531 can partially disrupt these changes and thus alleviate the hyperoxia-induced alveolar epithelial cell injury.

Evaluation of mild hypothermia therapy for neonatal hypoxic-ischaemic encephalopathy on brain energy metabolism using 18F-fluorodeoxyglucose positron emission computed tomography.

It remains unclear whether mild hypothermia affects energy metabolism in the brain tissue of newborns with hypoxic-ischaemic encephalopathy (HIE). The current study aimed to investigate the effect of mild hypothermia on energy metabolism in neonatal HIE and assess brain energy metabolism using position emission tomography/computed tomography (PET/CT) scanning. The mean standardised uptake values of 18F-fluorodeoxyglucose (18F-FDG) were used to determine the glucose metabolic rate in various brain anatomical regions, including the thalamus, basal ganglia and the frontal, parietal and occipital lobes. The rate of glucose metabolism significantly improved following treatment with mild hypothermia therapy and conventional therapy (P<0.001). Prior to the treatment, no significant differences were identified between the groups (P>0.05). Following treatment, the rate of glucose metabolism was significantly improved in the mild hypothermia therapy group compared with that in the conventional therapy group (P<0.001). Thus, these results indicate that mild hypothermia therapy effectively promotes the recovery of patients with neonatal HIE. 18F-FDG PET/CT scanning may be used to provide reference values for the assessment of energetic metabolism in patients with neonatal HIE.

One-step synthesis of water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission.

Water-soluble hexagonal NaScF4:Yb/Er nanocrystals have been directly synthesized via a facile one-step hydrothermal route. The as-prepared nanocrystals were monodisperse and could form stable colloidal solutions in polar solvents, such as water and ethanol. The novel NaScF4:Yb/Er nanocrystals exhibited intrinsic intense red upconversion emission, in contrast to other lanthanide-doped fluoride nanocrystals. Remarkably, the upconversion emission intensity was enhanced ∼6.8 times through the coating of an active-shell (containing Yb(3+)) surrounding the NaScF4:Yb/Er core nanocrystals, owing to surface passivation effect and efficient energy transfer from Yb(3+) ions in both the core and the shell to Er(3+) ions. These water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission are ideal for a variety of in vitro and in vivo biological imaging applications.

NaYF4 nanocrystals with intense 1530 nm fluorescence for polymer optical waveguide amplifiers.

Alfa-NaYF4:18%Yb,0.2%Er nanocrystals have been synthesized. The average size of nanocrystals is 15 nm. The fluorescence spectra of the nanocrystals excited under 980 nm LD was recorded. An optical waveguide amplifier was fabricated using SU-8 2005 polymer doped with 0.21 wt% of nanocrytals. For an input signal power of 0.05 mW and a pump power of 212 mW, a relative optical gain of 3.3 dB at 1520 nm was achieved.

Oleic acid-modified LiYF4:Er,Yb nanocrystals for potential optical-amplification applications.

LiYF4:18%Yb, 2%Er nanocrystals and NaYF4:18%Yb,2% Er nanoparticles (NCs) were synthesized by a solvothermal approach using oleic acid (OA) as the surfactant. With the excitation of a 980 nm diode laser, LiYF4:18%Yb, 2%Er NCs exhibit more strong emission than alpha-NaYF4:18%Yb, 2%Er at around 1530 nm. The TEM images showed that the LiYF4:18%Yb, 2%Er NCs have a nearly spherical shape and the size is about 15 nm. The OA-capped LiYF4 NCs have excellent dispersibility in organic solvents. These results showed that LiYF4:18%Yb, 2%Er NCs are a promising material for polymer-based optical waveguide amplifiers.