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The thermal decomposition products and kinetics of two typical organic−inorganic halide perovskites, CH 3 NH 3 PbI 3 (MAPbI 3 ) and HC(NH 2 ) 2 PbI 3 (FAPbI 3 ), were investigated via simultaneous thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. NH 3 and CH 3 I were verified as the major thermal decomposition gases of MAPbI 3 . Furthermore, for the first time, methane (CH 4 ) was observed as a thermal degradation product of MAPbI 3 at elevated temperatures. In contrast to conventional wisdom, (HCN) 3 (trimerized HCN) and NH 3 were demonstrated as the major gaseous decomposition products of FAPbI 3 at lower temperatures, while HCN and NH 3 became dominant at high temperatures (>360 °C). The hybrid experimental/theoretical results presented in this study will further our understanding of the perovskite decomposition mechanism and provide new insights into designing of long-term stable perovskite-based devices.

Light-emitting diodes (LEDs) based on lead halide perovskites demonstrate outstanding optoelectronic properties and are strong competitors for display and lighting applications. While previous halide perovskite LEDs are mainly produced via solution processing, here an all-vacuum processing method is employed to construct CsPbBr 3 LEDs because vacuum processing exhibits high reliability and easy integration with existing OLED facilities for mass production. The high-throughput combinatorial strategies are further adopted to study perovskite composition, annealing temperature, and functional layer thickness, thus significantly speeding up the optimization process. The best rigid device shows a current efficiency (CE) of 4.8 cd A −1 (EQE of 1.45%) at 2358 cd m −2 , and best flexible device shows a CE of 4.16 cd A −1 (EQE of 1.37%) at 2012 cd m −2 with good bending tolerance. Moreover, by choosing NiO x as the hole-injection layer, the CE is improved to 10.15 cd A −1 and EQE is improved to a record of 3.26% for perovskite LEDs produced by vacuum deposition. The time efficient combinatorial approaches can also be applied to optimize other perovskite LEDs.

Carrier lifetime in flexible CH3NH3PbI3 films increases with increasing tensile strain, and conversely decreases with increasing compressive strain.

BackgroundPolymethylmethacrylate bone cement cannot provide an adhesive chemical bonding to form a stable cement-bone interface. Bioactive bone cements show bone bonding ability, but their clinical application is limited because bone resorption is observed after implantation. Porous polymethylmethacrylate can be achieved with the addition of carboxymethylcellulose, alginate and gelatin microparticles to promote bone ingrowth, but the mechanical properties are too low to be used in orthopedic applications. Bone ingrowth into cement could decrease the possibility of bone resorption and promote the formation of a stable interface. However, scarce literature is reported on bioactive bone cements that allow bone ingrowth. In this paper, we reported a porous surface modified bioactive bone cement with desired mechanical properties, which could allow for bone ingrowth.Materials and MethodsThe porous surface modified bioactive bone cement was evaluated to determine its handling characteristics, mechanical properties and behavior in a simulated body fluid. The in vitro cellular responses of the samples were also investigated in terms of cell attachment, proliferation, and osteoblastic differentiation. Furthermore, bone ingrowth was examined in a rabbit femoral condyle defect model by using micro-CT imaging and histological analysis. The strength of the implant–bone interface was also investigated by push-out tests.ResultsThe modified bone cement with a low content of bioactive fillers resulted in proper handling characteristics and adequate mechanical properties, but slightly affected its bioactivity. Moreover, the degree of attachment, proliferation and osteogenic differentiation of preosteoblast cells was also increased. The results of the push-out test revealed that higher interfacial bonding strength was achieved with the modified bone cement because of the formation of the apatite layer and the osseointegration after implantation in the bony defect.ConclusionsOur findings suggested a new bioactive bone cement for prosthetic fixation in total joint replacement.

In this study, biphasic calcium phosphate (BCP) porous scaffolds with controllable phase compositions, controllable macropore percentages, and thus adjustable properties were in situ prepared by sintering a series of composites consisted of calcium phosphate cement (CPC) and porous resin negative mold made from rapid prototyping (RP) technique. The CPC pastes were formed by mixing a powder mixture of tetracalcium phosphate and anhydrous dicalcium phosphate with liquid phase of diluted phosphate acid solution. Results show that the phase composition was easily adjustable by controlling both weight ratio of the powder mixture to the liquid phase (P/L) and concentration of the liquid phase. The macropore structure of the BCP scaffold can be regulated by using different RP negative molds. Through in vitro compressive strength (CS) and immersion tests, it was demonstrated that both macropore percentage and phase composition played important roles in the CS and also the dissolving rates of the scaffolds. As the macropore percentage of the scaffold increased, its CS decreased but the dissolving rate increased; also, as the weight ratio of hydroxyapatite to tricalcium (HA/TCP) in the scaffold increased, the CS first increased and then decreased but the dissolving rate uniformly decreased. The CS values of the BCP scaffolds with a HA/TCP weight ratio of 59:41 were 5.84 +/- 1.16 MPa for a total porosity of approximately 67.67% containing a macropore percentage of 30%, and 3.34 +/- 0.79 MPa for a total porosity of approximately 70.90% containing a macropore percentage of 50%, respectively, comparable to the corresponding levels of human cancellous bone (2-12 MPa).

In previous studies, we developed a new type of Sr-incorporated hydroxyapatite cement (Sr-HAC), which was shown to have many excellent physiochemical properties, by an ionic cement route (Guo et al., Biomaterials 2005;26:4073-4083). As a further study, the main aims of this article were to examine the Sr-HAC's in vitro biocompatibility, including acute toxicity, hemolytic reaction, pyrogen reaction, and cytoxicity, to evaluate its in vivo degradability during intramuscular and femur implantation, and also to investigate the influence of Sr doses on these properties. The in vitro results show that all of the Sr-HAC samples exhibit satisfactory biocompatibility, and the Sr/(Sr+Ca) molar ratio has an important effect on these properties. For example, the Sr-HAC with a Sr/(Sr+Ca) molar ratio of 5% (5% Sr-HAC) has higher biocompatibility than both the one with a Sr/(Sr+Ca) molar ratio of 10% (10% Sr-HAC) and the Sr-free one. The in vivo results of both the rabbit intramuscular and femur implantation experiments show that the Sr-HAC samples exhibit a much faster degradation rate than the Sr-free one, and that this also depends on the Sr/(Sr+Ca) molar ratio. Specifically, the mean degradation rate of the 10% Sr-HAC increases by an amplitude of 73.9 wt % compared with that of the Sr-free HAC. In addition, the optical transmission photographs show that the Sr doses play an important role on the interface between the implants and the new bone. The energy dispersion X-ray spectrum analysis indicates that there exists a gradient distribution of Sr element in the tight and bioactive interface between the implants and new bone, indicating that the Sr element takes a share in the mineralization of the new bone together with Ca element.

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