Fundamental Importance For Rational Design Research Articles

(Invited) Crystal Engineering of Bismuth Vanadate for Enhanced Light-Driven Water Oxidation

Photocatalytic and photoelectrochemical processes employing photoactive semiconductors are two key systems in harvesting sunlight for energy and environmental applications. Strategies have been formulated to improve the properties of the semiconductor for better performances. However, requirements to yield excellent performances are different in these two distinctive systems. Understanding of the underlying mechanism for the photoexcited charge transportation in relation to their photoactivities is of fundamental importance for rational design of high-performing photoactive materials, which may serve as a useful guideline for the fabrication of good photocatalysts or photoelectrodes toward sustainable solar fuels generation. Many photoactive semiconductors, including bismuth vanadate, are having inadequate charge transport properties such as low charge mobility, short lifetime, and slow surface kinetics. Standalone single photoactive semiconductors also faces the challenge of meeting the needs for large redox potentials with a sufficiently narrow bandgap for visible light absorption. Coupling two or more components into a photoactive composite may address some of these drawbacks by utilizing the strengths of the individual semiconductors. In this presentation, the charge transportation behavior of single component photoactive semiconductor based on bismuth vanadate, and the composite materials forming heterojunction with bismuth vanadate, will be examined and discussed (example of modulation of BiVO4 photocatalyst in Figure 1 ).1 Typically, crystal facet engineering, interfacing with non-photoactive secondary component, and narrowing the crystal size into quantum-confinement region, will be the three strategies to be shared with audience during the presentation. Preferential charge migration depending on the crystal facet has been reported in various photocatalysts. These promoted charge migration can be further boosted with spatially deposited cocatalysts on the selective redox sites. The manipulation of crystal facet allows the controlled electron transfer to induce 4-electron process (oxygen evolution) or 2-electron process (hydrogen peroxide evolution) in water oxidation. Nanosizing the bismuth vanadate into <10 nm region with distinctive yet interconnected crystal domains leads to the expansion of band structure. Conduction band of bismuth vanadate was expanded to energetic level capable of reducing proton into H2. The traditional O2-evolving bismuth vanadate is now demonstrating H2-producing properties. Figure 1: Time-resolved microwave conductivity (TRMC) spectroscopy signals measured for BiVO4 and its Power-law decay fittings.Reference1. H. Wu, R. Irani, K. Zhang, L. Jing, H. Dai, H. Y. Chung, F. F. Abdi, Y. H. Ng*, Unveiling Carrier Dynamics in Periodic Porous BiVO4 Photocatalyst for Enhanced Solar Water Splitting. ACS Energy Lett. 2021, 6, 3400-3407. Figure 1

Identifying the role of Ni and Fe in Ni–Fe co-doped orthorhombic CoSe2 for driving enhanced electrocatalytic activity for oxygen evolution reaction

Exploring the origin of high electrocatalytic activity of Ni–Fe–Co ternary selenides for oxygen evolution reaction (OER) is of fundamental importance for rational design of efficient electrocatalysts. In this report, we synthesize self-assembled microspheres by orthorhombic CoSe2 nanorods along with the Ni and/or Fe doped counterparts, and systematically investigate their electrocatalytic performance. The results show that, although either Ni-doping or Fe-doping can significantly enhance the catalytic activity of CoSe2, the ways they promote catalytic activity are different. The Tafel analysis demonstrates that Fe incorporation leads to a kinetics change in the OER while Ni incorporation has little effect. Based on the electrochemical characterizations and theoretical calculations, Ni-doping maintains Co active sites and does not alter the OER mechanism, but decreases the energy barrier of the rate-limiting step by modifying Co active sites. In contrast, Fe-doping transforms the active sites from Co to Fe, and the rate-limiting step changes to the O–OH formation stage, thus affording faster reaction kinetics. These findings are further confirmed by more Ni–Fe co-doped CoSe2 with various content of Ni and Fe. Specifically, under the optimal experimental conditions, Ni–Fe co-doped CoSe2 (Ni0.04Fe0.16Co0.8Se2) exhibits a remarkable OER activity with an overpotential of ∼230 mV at 10 mA cm−2 and Tafel slope of 39 mV dec−1.

Photocatalytic and Photoelectrochemical Systems: Similarities and Differences.

Photocatalytic and photoelectrochemical processes are two key systems in harvesting sunlight for energy and environmental applications. As both systems are employing photoactive semiconductors as the major active component, strategies have been formulated to improve the properties of the semiconductors for better performances. However, requirements to yield excellent performances are different in these two distinctive systems. Although there are universal strategies applicable to improve the performance of photoactive semiconductors, similarities and differences exist when the semiconductors are to be used differently. Here, considerations on selected typical factors governing the performances in photocatalytic and photoelectrochemical systems, even though the same type of semiconductor is used, are provided. Understanding of the underlying mechanisms in relation to their photoactivities is of fundamental importance for rational design of high-performing photoactive materials, which may serve as a general guideline for the fabrication of good photocatalysts or photoelectrodes toward sustainable solar fuel generation.

Optimizing particle size of docetaxel-loaded micelles for enhanced treatment of oral epidermoid carcinoma

Understanding how the size of nanocarriers affects their fate in biological systems in vivo is of fundamental importance for rational design of drug delivery systems. In this study, five docetaxel (DTX)-loaded methoxy poly(ethylene glycol)-poly(lactide) micelles of different sizes (30-230nm) were prepared. It was observed that the permeation of micelles within both the multicellular tumor spheroids and tumor xenografts in mice was dependent on the size of the micelle. In addition, the size of micelles influenced their pharmacokinetic behavior. DTX-loaded pH-sensitive micelle based on poly(ethylene glycol)-poly(lactide)-poly(β-amino ester) (DTX-pHPM) was constructed to further illustrate the effect of particle size. As expected, DTX-pHPM improved tumor penetration, uptake by tumor cells, and prolonged circulation time, consequently demonstrating the highest inhibition of in vivo tumor growth (84.4%) in oral epidermoid carcinoma. Taken together, our findings can aid in designing nano-scale drug delivery systems for cancer therapy by optimizing the particle size.

Global Analysis of Protein Expression and Phosphorylation of Three Stages of Plasmodium falciparum Intraerythrocytic Development

During asexual intraerythrocytic development, Plasmodium falciparum diverges from the paradigm of the eukaryotic cell cycles by undergoing multiple rounds of DNA replication and nuclear division without cytokinesis. A better understanding of the molecular switches that coordinate a myriad of events for the progression of the parasite through the intraerythrocytic developmental stages will be of fundamental importance for rational design of intervention strategies. To achieve this goal, we performed isobaric tag-based quantitative proteomics and phosphoproteomics analyses of three developmental stages in the Plasmodium asexual cycle and identified 2767 proteins, 1337 phosphoproteins, and 6293 phosphorylation sites. Approximately 34% of identified proteins and 75% of phosphorylation sites exhibit changes in abundance as the intraerythrocytic cycle progresses. Our study identified 43 distinct phosphorylation motifs and a range of potential MAPK/CDK substrates. Further analysis of phosphorylated kinases identified 30 protein kinases with 126 phosphorylation sites within the kinase domain or in N- or C-terminal tails. Many of these phosphorylations are likely CK2-mediated. We define the constitutive and regulated expression of the Plasmodium proteome during the intraerythrocytic developmental cycle, offering an insight into the dynamics of phosphorylation during asexual cycle progression. Our system-wide comprehensive analysis is a major step toward defining kinase-substrate pairs operative in various signaling networks in the parasite.