Excitonic effects mediated by Coulomb interactions between photogenerated electrons and holes play crucial roles in photoinduced processes of semiconductors. In terms of photocatalysis, however, ...efforts have seldom been devoted to the relevant aspects. For the catalysts with giant excitonic effects, the coexisting, competitive exciton generation serves as a key obstacle to the yield of free charge carriers, and hence, transformation of excitons into free carriers would be beneficial for optimizing the charge-carrier-involved photocatalytic processes. Herein, by taking bismuth oxybromide (BiOBr) as a prototypical model system, we demonstrate that excitons can be effectively dissociated into charge carriers with the incorporation of oxygen vacancy, leading to excellent performances in charge-carrier-involved photocatalytic reactions such as superoxide generation and selective organic syntheses under visible-light illumination. This work not only establishes an in-depth understanding of defective structures in photocatalysts but also paves the way for excitonic regulation via defect engineering.
Two-dimensional nanosheets have attracted tremendous attention because of their promising practical application and theoretical values. The atomic-thick nanosheets are able to not only enhance the ...intrinsic properties of their bulk counterparts but also give birth to new promising properties. Herein, we highlight an available pathway to prepare the ultrathin graphitic-phase C3N4 (g-C3N4) nanosheets by a “green” liquid exfoliation route from bulk g-C3N4 in water for the first time. The as-obtained ultrathin g-C3N4 nanosheet solution is very stable in both the acidic and alkaline environment and shows pH-dependent photoluminenscence (PL). Compared to the bulk g-C3N4, ultrathin g-C3N4 nanosheets show enhanced intrinsic photoabsorption and photoresponse, which induce their extremely high PL quantum yield up to 19.6%. Thus, benefiting from the inherent blue light PL with high quantum yields and high stability, good biocompatibility, and nontoxicity, the water-soluble ultrathin g-C3N4 nanosheet is a brand-new but promising candidate for bioimaging application.
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•Micro-mesoporous UiO-66 was synthesized with P123 as structure-directing agent.•Micro-mesoporous UiO-66 shows 2.6 times toluene adsorption capacity of UiO-66.•Micro-mesoporous ...structure improves the mass transfer rate and adsorption capacity.•Efficient regeneration of exhausted adsorbent was achieved by heating.
In this work, micro-mesoporous UiO-66 was successfully prepared with P123 (EO20PO70EO20) as structure-directing agent by a simple solvothermal method. Adsorption/desorption kinetics of gaseous toluene over pristine UiO-66 and micro-mesoporous UiO-66 were investigated by breakthrough experiments, toluene vapor adsorption isotherm measurements and temperature programmed desorption (TPD) experiments. The interactions between toluene and UiO-66 samples were assessed through the Henry’s law constant (KH) and the isosteric adsorption heat (ΔHads). The micro-mesoporous UiO-66 crystal demonstrated 2.6 times toluene adsorption capacity of the pristine UiO-66 when the P123/Zr4+ molar ratio was 0.2. Results showed that micropore adsorption was the main adsorption process and the larger pores in micro-mesoporous UiO-66 increased molecular diffusion rate and reduced the mass transfer resistance. This result indicated that micro-mesoporous structures and defect sites had a positive effect on toluene molecules capture. The breakthrough times and the working capacities decreased with the increase of the relative humidity and adsorption temperature. A good thermal stability and reproducibility were revealed over the micro-mesoporous UiO-66 in this paper.
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Batch experiments were conducted to study the Cr(VI) removal by nanoscale zero valent iron and copper intercalated montmorillonite (MMT-nFe0/Cu0) nanocomposite. MMT-nFe0/Cu0 was ...characterized using SEM, TEM, XRD, FTIR, N2 adsorption–desorption isotherms and XPS. The results demonstrated that highly dispersed nanoscale Fe0/Cu0 (nFe0/Cu0) were successfully introduced into the montmorillonite (MMT) layers. In the reaction process, the combination of Cu0 and Fe0 acted as a galvanic cell, and electrocorrosion not only speeded up the reaction rate, but also increased reduction activity of nFe0. MMT-nFe0/Cu0 as an excellent carrier had good functions in dispersing nFe0 and Cu0 particles, pH buffering and could keep nFe0 and Cu0 particles from being released. Besides, no iron ions and very low concentrations of copper ions released in the reaction system, which greatly avoided the influence of secondary environmental pollution.
Purpose:
Intensity modulated proton therapy (IMPT) is highly sensitive to range uncertainties and uncertainties caused by setup variation. The conventional inverse treatment planning of IMPT ...optimized based on the planning target volume (PTV) is not often sufficient to ensure robustness of treatment plans. In this paper, a method that takes the uncertainties into account during plan optimization is used to mitigate the influence of uncertainties in IMPT.
Methods:
The authors use the so-called “worst-case robust optimization” to render IMPT plans robust in the face of uncertainties. For each iteration, nine different dose distributions are computed—one each for ± setup uncertainties along anteroposterior (A-P), lateral (R-L) and superior–inferior (S-I) directions, for ± range uncertainty, and the nominal dose distribution. The worst-case dose distribution is obtained by assigning the lowest dose among the nine doses to each voxel in the clinical target volume (CTV) and the highest dose to each voxel outside the CTV. Conceptually, the use of worst-case dose distribution is similar to the dose distribution achieved based on the use of PTV in traditional planning. The objective function value for a given iteration is computed using this worst-case dose distribution. The objective function used has been extended to further constrain the target dose inhomogeneity.
Results:
The worst-case robust optimization method is applied to a lung case, a skull base case, and a prostate case. Compared with IMPT plans optimized using conventional methods based on the PTV, our method yields plans that are considerably less sensitive to range and setup uncertainties. An interesting finding of the work presented here is that, in addition to reducing sensitivity to uncertainties, robust optimization also leads to improved optimality of treatment plans compared to the PTV-based optimization. This is reflected in reduction in plan scores and in the lower normal tissue doses for the same coverage of the target volume when subjected to uncertainties.
Conclusions:
The authors find that the worst-case robust optimization provides robust target coverage without sacrificing, and possibly even improving, the sparing of normal tissues. Our results demonstrate the importance of robust optimization. The authors assert that all IMPT plans should be robustly optimized.
Limited by the relatively sluggish charge‐carrier separation in semiconductors, the photocatalytic performance is still far below what is expected. Herein, a model of ZnIn2S4 (ZIS) nanosheets with ...oxygen doping is put forward to obtain in‐depth understanding of the role that doping atoms play in photocatalysis. It shows enhanced photocatalytic activity compared with pristine ZIS. The electron dynamics analyzed by ultrafast transient absorption spectroscopy reveals that the average recovery lifetime of photoexcited electrons is increased by 1.53 times upon oxygen incorporation into the ZIS crystals, indicating enhanced separation of photoexcited carriers in oxygen‐doped ZIS nanosheets. As expected, the oxygen‐doped ZIS nanosheets show a remarkably improved photocatalytic activity with a hydrogen evolution rate of up to 2120 μmol h−1 g−1 under visible‐light irradiation, which is 4.5 times higher than that of the pristine ZIS nanosheets.
Doping control: A model of ultrathin ZnIn2S4 nanosheets with oxygen doping offers insights into the influence of oxygen doping on the separation of photogenerated electron–hole pairs and the photocatalytic activity of catalysts at the atomic level. Experimental and theoretical studies reveal that the oxygen‐doped ZnIn2S4 ultrathin nanosheets have enhanced photocatalytic activity.
Nonhuman primates (NHPs) are the closest living relatives of humans and play a critical and unique role in neuroscience research and pharmaceutical development. General anesthesia is usually required ...in neuroimaging studies of NHPs to keep the animal from stress and motion. However, the adverse effects of anesthesia on cerebral physiology and neural activity are pronounced and can compromise the data collection and interpretation. Functional connectivity is frequently examined using resting-state functional MRI (rsfMRI) to assess the functional abnormality in the animal brain under anesthesia. The fMRI signal can be dramatically suppressed by most anesthetics in a dose-dependent manner. In addition, rsfMRI studies may be further compromised by inter-subject variations when the sample size is small (as seen in most neuroscience studies of NHPs). Therefore, proper use of anesthesia is strongly demanded to ensure steady and consistent physiology maintained during rsfMRI data collection of each subject. The aim of this review is to summarize typical anesthesia used in rsfMRI scans of NHPs and the effects of anesthetics on cerebral physiology and functional connectivity. Moreover, the protocols with optimal rsfMRI data acquisition and anesthesia procedures for functional connectivity study of macaque monkeys are introduced.
Organolead halide perovskites have attracted extensive attentions as light harvesting materials for solar cells recently, because of its high charge‐carrier mobilities, high photoconversion ...efficiencies, low energy cost, ease of deposition, and so on. Herein, with CH3NH3PbI3 film deposited on flexible ITO coated substrate, the first organolead halide perovskite based broadband photodetector is demonstrated. The organolead halide perovskite photodetector is sensitive to a broadband wavelength from the ultraviolet light to entire visible light, showing a photo‐responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19×103%, 5.84% at 365 nm and 780 nm with a voltage bias of 3 V, respectively. Additionally, the as‐fabricated photodetector exhibit excellent flexibility and robustness with no obvious variation of photocurrent after bending for several times. The organolead halide perovskite photodetector with high sensitivity, high speed and broad spectrum photoresponse is promising for further practical applications. And this platform creates new opportunities for the development of low‐cost, solution‐processed and high‐efficiency photodetectors.
Organometal halide perovskites have shown tremendous potential as incident light absorbers for optoelectronic applications. In this work, a broadband photodetecotor is demonstrated based on the CH3NH3PbI3 film, showing a photo‐responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19 × 103 %, 5.84% at 365 and 780 nm, respectively. These results provide new opportunities for the development of high‐efficiency photodetectors.
Electrochemical water splitting is a clean technology for H2 fuels, but greatly hindered by the slow kinetics of the oxygen evolution reaction (OER). Herein, a series of spinel‐structured nanosheets ...with oxygen deficiencies and ultrathin thicknesses were designed to increase the reactivity and the number of active sites of the catalysts, which were then taken as an excellent platform for promoting the water oxidation process. Theoretical investigations showed that the oxygen vacancies confined in the ultrathin nanosheet could lower the adsorption energy of H2O, leading to increased OER efficiency. As expected, the NiCo2O4 ultrathin nanosheets rich in oxygen vacancies exhibited a large current density of 285 mA cm−2 at 0.8 V and a small overpotential of 0.32 V, both of which are superior to the corresponding values of bulk samples or samples with few oxygen deficiencies and even higher than those of most reported non‐precious‐metal catalysts. This work should provide a new pathway for the design of advanced OER catalysts.
Beneficial deficiencies: A series of spinel‐structured nanosheets with oxygen deficiencies (Ovac) and ultrathin thicknesses were synthesized for the first time. These features lead to an increase in the number of active sites and in the activity of the catalyst in water oxidation, which was confirmed by experimental and theoretical studies.
Highlights
This review introduces nanozymes that exhibit different enzymatic activities and emphasizes the advantages of nanozymes over natural enzymes.
The roles of nanozymes in different cancer ...diagnostic and therapeutic technologies are summarized, explained by representative examples.
The potential challenges of nanozyme-based cancer theranostics are outlined, and future research directions are outlooked.
Natural enzymes usually suffer from high production cost, ease of denaturation and inactivation, and low yield, making them difficult to be broadly applicable. As an emerging type of artificial enzyme, nanozymes that combine the characteristics of nanomaterials and enzymes are promising alternatives. On the one hand, nanozymes have high enzyme-like catalytic activities to regulate biochemical reactions. On the other hand, nanozymes also inherit the properties of nanomaterials, which can ameliorate the shortcomings of natural enzymes and serve as versatile platforms for diverse applications. In this review, various nanozymes that mimic the catalytic activity of different enzymes are introduced. The achievements of nanozymes in different cancer diagnosis and treatment technologies are summarized by highlighting the advantages of nanozymes in these applications. Finally, future research directions in this rapidly developing field are outlooked.
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