Search

Shortening channels to the feature length of polymer domains is important to understand the charge transport in semiconducting polymers from macroscopic to microscopic scales. In this work, we fabricated polymer transistors with sub-domain-size channels by electron-beam lithography and asymmetrically aligned domains by off-center spin coating, in which a dry self-patterning method with hexagonal boron nitride was developed to eliminate parasitic leakage. The current sharply increased by 60 times when the channel length was shortened from 200 to 80 nm. The device with an 80 nm-long channel in the direction parallel to the aligned polymer domains delivered a saturation current 160 times higher than that of the orthogonal counterpart. These results and a velocity calculation suggested that the bottleneck of charge transport in electronic devices is domain boundaries. These results highlight the importance of high-efficiency intra-domain charge transport and also the inter-domain limitation. Our findings will contribute to further polymer optimization to improve the performance of polymer devices.

Microorganisms are applied to remediate chromium (Cr)-contaminated soil extensively. Nevertheless, the microbial loss and growth inhibition in the soil environment restrain the application of this technology. In this study, a Cr(VI)-reducing strain named Bacillus cereus WHX-1 was screened, and the microbial aggregates system was established via immobilizing the strain on Enteromorpha prolifera biochar to enhance the Cr(VI)-reducing activity of this strain. The mechanism of the system on Cr(VI) transformation in Cr-contaminated soil was illuminated. Pot experiments indicated that the microbial aggregates system improved the physicochemical characteristics of Cr-contaminated soil obviously by increasing organic carbon content and cation exchange capacity, as well as decreasing redox potential and bulk density of soil. Moreover, 94.22% of Cr(VI) was transformed into Cr(III) in the pot, and the content of residue fraction Cr increased by 63.38% compared with control check (CK). Correspondingly, the physiological property of Ryegrass planted on the Cr-contaminated soil was improved markedly and the main Cr(VI)-reducing microbes, Bacillus spp., were enriched in the soil with a relative abundance of 28.43% in the microbial aggregates system. Considering more active sites of biochar for microbial aggregation, it was inferred that B. cereus WHX-1 could be immobilized by E. prolifera biochar, and more Cr(VI) was transformed into residue fraction. Cr stress was decreased and the growth of plants was enhanced. This study would provide a new perspective for Cr-contaminated soil remediation.

The precise detection of PD-1/PD-L1 biomarkers helps to predict the prognosis of corresponding immunotherapy. 125I-labeled nivolumab targeting activated immune cells infiltrating the tumorous tissues was developed to evaluate the expression of PD-1 immune checkpoints. SPECT images indicated that 125I–nivolumab preferentially targeted to tumor-surrounded immune cells. This radiotracer can dynamically and quantitatively characterize the in vivo expression of immune checkpoints for colorectal cancer, thereby potentially enabling the early screening of patients, monitoring the efficacy of treatment, and assessing potential immunotoxicity.

Performance characteristics, such as dark current and response time, of ZnO nanowire (NW) photodetectors are usually degraded by H2O/O2 adsorption on the NW surfaces. In this work, ZnO NW photodetectors based on Au Schottky contact through passivating surface states were investigated. ZnO NW photodetectors were fabricated with a lateral electrode structure, in which Au served as Au/ZnO Schottky contact and semi-transparent top electrode. Specifically, passivation of the surface states of ZnO NWs by using highly intensive UV irradiation effectively improved the photoresponse. A physical model based on surface band theory was developed to understand the origin of the performance improvement of the photodetector. The present device architecture prevents ZnO NWs photodetector from H2O/O2 adsorption in air and efficiently extracts photogenerated carriers across a diametrical direction.

In the above letter [1] , the corresponding authors should be Yong Xu (xuyong@njupt.edu.cn), Huabin Sun (hbsun@ njupt.edu.cn), and Yi Shi (yshi@nju.edu.cn).

Field-effect transistors based on conjugated polymers have reached mobilities comparable to those of polysilicon rivals and recently demonstrated self-healing capability, indicating their great potential for use in future plastic electronics. For practical applications, the operating speed of polymer transistors must be increased, which requires not only high mobility but also short channel length. Decreasing channel length is an important engineering issue for high-frequency operation and high-density integration. However, shortening channel length has proved challenging because of the poor compatibility of conjugated polymer transistors with conventional lithography; i.e., fragile polymer semiconductor films may be damaged during lithographic processes. The underlying device physics, particularly of those with short channels, remain poorly understood. Here, we fabricated polymer transistors with channel lengths below 1000 nm. A dry self-patterning process lowered the gate leakage current to less than 10–12 A, enabling quantitative analysis of devices with very short channels. We found that a high Schottky barrier with a sizable space-charge region (>1 μm) was responsible for the high off-state current because the space-charge zones at the source and drain joined when the channel was short, lowering the energy barrier to carrier diffusion in the off state. Such diffusion was suppressed simply by controlling the molecular alignment so that the deep traps distributed at the domain boundaries limited the carrier diffusion and thus suppressed the off-state current.

Metallic cavities show substantial advantages in light confinement, providing opportunities to modulate the optical resonances and absorption. Here, we report on the configuration of horizontally aligned ZnO-nanowires-based metallic cavity ensemble with a light to dark current ratio of ~1000. An enhanced polarization photodetection ratio of transverse electric (TE) to transverse magnetic (TM) was experimentally observed compared to the single ZnO nanowire photodetector. Finite difference time domain simulation were performed on the metallic cavities, showing the distinct resonance behaviors under TE and TM light. The confinement by the multi-reflection and optical resonances between the metallic claddings contribute to the high anisotropy ratio. Furthermore, the polarized light absorption in the metallic cavity was studied as well as in the naked nanowire, which reveal a significant dependence on the cavity diameter and wavelength. For the metallic cavities, the absorption ratio of TE to TM show an enhanced value in the range of 300~500 nm wavelength and 85~150 diameter and a reversed value in the range of 400~500 nm wavelength and 17~50 diameter. While for the naked nanowires, the ratio show an apparently opposite value in these two regions. The presented metallic cavities demonstrate a specific paradigm of optical engineering in nanoscale and potentially helps the development of optoelectronic devices.

Ultraviolet electroluminescence from Schottky type LED device is demonstrated. The device prototype is based on Schottky junctions formed between Au and the top ends of ZnO nanowire arrays. Rectifying current-voltage characteristics are observed, and three different charge transport mechanisms are discussed in detail. Excitonic electroluminescence at around 380 nm is detected at high forward bias and the linear relationship between intensity and current suggests a LED device performance. The observation of LED signals from the simple Schottky structure provides a potential supplement to the category of ultraviolet LED devices.

A nonselective micropatterning method of self-assembled monolayers (SAMs) based on laser and phase-shifting mask (PSM) is demonstrated. Laser beam is spatially modulated by a PSM, and periodic SAM patterns are generated sequentially through thermal desorption. Patterned wettability is achieved with alternating hydrophilic/hydrophobic stripes on octadecyltrichlorosilane monolayers. The substrate is then used to assemble CdS semiconductor nanowires (NWs) from a solution, obtaining well-aligned NWs in one step. Our results show valuably the application potential of this technique in engineering SAMs for integration of functional devices.