Christopher S. Choi

High-rate capability of Na2FePO4F nanoparticles by enhancing surface carbon functionality for Na-ion batteries

Metal phosphate compounds are considered promising candidates as positive electrode materials for Na-ion batteries because they offer higher cation-insertion potentials than analogous metal oxides. One such example is sodium iron fluorophosphate (Na2FePO4F), a compound that is typically synthesized by high-temperature solid-state routes. In this study, we prepare phase-pure Na2FePO4F using the polyol route, a low-temperature process that allows for the synthesis of nanoparticles (15–25 nm), a form that enhances Na-ion insertion kinetics and cycling stability. We then apply two methods to enhance the electronic conductivity of Na2FePO4F: (i) converting residual organic byproducts of the polyol synthesis to conductive carbon coatings; and (ii) preparing a nanocomposite with reduced graphene oxide. The resulting electrode materials are characterized in nonaqueous Na-ion electrolytes, assessing such metrics as specific capacity, rate capability, and cycling stability. A thorough electrochemical kinetics analysis is performed to deconvolve surface-vs.-bulk Na-ion insertion as a function of composite structure. Specific capacities between 60–110 mA h g−1 were achieved in galvanostatic charge–discharge tests when cycling in the range from 10C to C/10, respectively.

Tuning Molecular Interactions for Highly Reproducible and Efficient Formamidinium Perovskite Solar Cells via Adduct Approach

The Lewis acid-base adduct approach has been widely used to form uniform perovskite films, which has provided a methodological base for the development of high-performance perovskite solar cells. However, its incompatibility with formamidinium (FA)-based perovskites has impeded further enhancement of photovoltaic performance and stability. Here, we report an efficient and reproducible method to fabricate highly uniform FAPbI3 films via the adduct approach. Replacement of the typical Lewis base dimethyl sulfoxide (DMSO) with N-methyl-2-pyrrolidone (NMP) enabled the formation of a stable intermediate adduct phase, which can be converted into a uniform and pinhole-free FAPbI3 film. Infrared and computational analyses revealed a stronger interaction between NMP with the FA cation than DMSO, which facilitates the formation of a stable FAI·PbI2·NMP adduct. On the basis of the molecular interactions with different Lewis bases, we proposed criteria for selecting the Lewis bases. Owed to the high film quality, perovskite solar cells with the highest PCE over 20% (stabilized PCE of 19.34%) and average PCE of 18.83 ± 0.73% were demonstrated.

Synthesis and Properties of a Photopatternable Lithium‐Ion Conducting Solid Electrolyte

One of the important considerations for the development of on-chip batteries is the need to photopattern the solid electrolyte directly on electrodes. Herein, the photopatterning of a lithium-ion conducting solid electrolyte is demonstrated by modifying a well-known negative photoresist, SU-8, with LiClO4 . The resulting material exhibits a room temperature ionic conductivity of 52 µS cm-1 with a wide electrochemical window (>5 V). Half-cell galvanostatic testing of 3 µm thin films spin-coated on amorphous silicon validates its use for on-chip energy-storage applications. The modified SU-8 possesses excellent mechanical integrity, is thermally stable up to 250 °C, and can be photopatterned with micrometer-scale resolution. These results present a promising direction for the integration of electrochemical energy storage in microelectronics.

462. Busulfan Dose Escalation to Increase Gene Marking of Hematopoietic Stem Cells by Lentiviral Vectors in Infant Rhesus Monkeys

Top of pageAbstract In clinical allogeneic bone marrow transplantation (BMT), complete myeloablation with high-dose busulfan (16 mg/kg) is often used to |[ldquo]|make space|[rdquo]| for the graft in the recipient BM compartment. As this treatment has significant toxicity, we sought to establish a low-dose busulfan protocol for partial myeloablation in the context of a gene-modified autologous BMT. Also, for infants and young children, calculation of dosage based on body surface area (mg/m2) has been reported give more consistent circulating busulfan levels than dosages based on mass (kg). In this study we sought to identify an optimal busulfan dose that could result in efficient long-term gene marking with minimal toxicities. We performed a lentiviral gene-marking study in infant rhesus macaques using escalating doses of busulfan. BM (|[sim]|10 ml/kg) was collected for immunoselection, and followed by a single 2 hour i.v. infusion of busulfan. Monkeys were transplanted using busulfan at 0, 40, 80, 120, and 160 mg/m2. Peripheral blood (PB) samples were collected for pharmacokinetic analysis up to 4 hours post-infusion, and the area under the curve (AUC) was determined. Isolated CD34+ cells were cultured for 24 hours in X-Vivo 15 with 100 ng/ml each of SCF, Flt3-L, and TPO. CD34+ cells were then transduced overnight with 4|[times]|10e7 infectious particles/ml of Simian Immunodeficiency Virus (SIV)-derived lentiviral vector pseudotyped with VSV-G on fibronectin-coated plates and using 4 |[mu]|g/ml protamine sulfate. The SIV vector contains a neomycin gene with a mutation in the start codon that abolishes its expression, and can therefore serve as a non-expressed marker gene. Transduced cells were washed and reinfused i.v 48 hours after administration of busulfan. Animals were monitored for myelosuppression, toxicity, and immune function. Increasing dosages of busulfan resulted in increased AUC. Some variability in AUC at each dose level was observed, suggesting inter-individual variations in busulfan absorption and clearance. At busulfan doses of 120 and 160 mg/m2, neutrophil and platelet counts transiently declined and were dose-dependent. No lymphopenia was observed, consistent with busulfan being myeloablative, but not immunosuppressive. Blood chemistries and behavior were normal in all animals, and no abnormalities were observed. PB and BM samples collected monthly were analyzed by real-time PCR to quantify gene marking. Gene marking levels have been fairly constant over the first 4 months post-transplant, ranging from undetectable in animals receiving no busulfan up to 0.1 % gene-containing cells in animals with the highest busulfan AUC. Together, these preliminary data suggest that (1) increased gene marking can be achieved by escalating busulfan doses, (2) busulfan is safe at the sub-myeloablative doses studied, and (3) while the anticipated myelosuppressive effects of busulfan were observed, there has been no evidence of adverse findings, to date.