Biomimetic Ag/ZnO@PDMS Hybrid Nanorod Array-Mediated Photo-induced Enhanced Raman Spectroscopy Sensor for Quantitative and Visualized Analysis of Microplastics.

Microplastics are persistent pollutants that accumulate in the environment and can cause serious toxicity to mammals. At present, few technologies are able to quantitatively detect chemicals and provide morphological information simultaneously. Herein, we developed a dragonfly-wing-mimicking ZnO nanorod array decorated with AgNPs on polydimethylsiloxane (PDMS) as a surface-enhanced Raman spectroscopy (SERS) and photo-induced enhanced Raman spectroscopy (PIERS) substrate for trace analysis of microplastics. The Ag/ZnO@PDMS hybrid nanorod array endows the sensor with high sensitivity and signal repeatability (RSD ∼ 5.89%), ensuring the reliable quantitative analysis of microplastics. Importantly, when the noble metal-semiconductor substrate was pre-radiated with ultraviolet light, a surprising PIERS was attained, achieving an additional enhancement of 11.3-fold higher than the normal SERS signal. By combining the PIERS technology with the "coffee ring effect", the sensor successfully discerned microplastics of polyethylene (PE) and polystyrene (PS) at a trace level of 25 µg/mL even with a portable Raman device. It was capable of identifying PS microspheres in contaminated tap water, lake water, river water, and seawater with detection limits of 25, 28, 35, and 60 µg/mL, respectively. The recovery rates of PS microspheres in four water environments ranged from 94.8 to 102.4%, with the RSD ranging from 2.40 to 6.81%. Moreover, quantitative and visualized detection of microplastics was readily realized by our sensor. This portable PIERS sensor represents a significant step toward the generalizability and practicality of quantitative and visual sensing technology.

TiO2 compact layer induced charge transfer enhancement in a three-dimensional TiO2-Ag array SERS substrate for quantitative and multiplex analysis.

A highly sensitive and uniform surface-enhanced Raman scattering (SERS) substrate is the guarantee for reliable quantitative analysis. Herein, a three-dimensional TiO2-Ag SERS substrate was prepared by growing a TiO2 nanorods (NRs) array on a TiO2 compact layer (c-TiO2), followed by modification with Ag nanoparticles (AgNPs). The synergy between the c-TiO2, semiconductor TiO2 NRs and the plasmonic AgNPs collaboratively endowed it with high sensitivity, in which c-TiO2 effectively blocked the recombination of electrons and holes, and the charge transfer enhancement contributed 10-fold improvement over that without the c-TiO2 substrate. Besides the high sensitivity, the TiO2-Ag hybrid array SERS substrate also showed quantitative and multi-component detecting capability. The limit of detection (LOD) for crystal violet (CV) was determined to be 10-9 M even with a portable Raman instrument. The TiO2-Ag composite structure was extended to detect organic pesticides (thiram, triazophos and fonofos), and the LODs for thiram, triazophos and fonofos were measured to be 10-7 M, 10-7 M and 10-6 M, respectively. In addition, the realistic simulation detecting pesticide residues for a real sample of dendrobium was demonstrated. The sensitive, quantitative and multiplex analysis of the TiO2-Ag hybrid array substrate indicated its great potential in the rapid detection of pesticide residues in real samples.

Lotus leaf mastoid inspired Ag micro/nanoarrays on PDMS film as flexible SERS sensor for in-situ analysis of pesticide residues on nonplanar surfaces.

Conventional surface-enhanced Raman scattering (SERS) molecular detection are based on hard and brittle substrate, which are not suitable for in-situ detection of analytes adsorbed on nonplanar surfaces. Here, we report a simple biomimetic synthesis method to fabricate lotus leaf mastoid structured AgNPs micro/nanoarrays as reliable SERS substrate. By ideal replicating mastoid structure of lotus leaf into a flexible and transparent PDMS film, followed by depositing plasmonic AgNPs, a powerful chemical sensor with high sensitivity and multiplex detecting capability is demonstrated. The employ of periodic mastoid structure array endows the sensor with high signal repeatability (RSD âˆ¼ 8.6 %), solving the general repeatability problem of SERS substrates. In addition, the detailed designed flexible and transparent PDMS substrate is capable of identifying trace analytes on curved surfaces with excellent durability. In the proof-of-concept experiment, a limit of detection (LOD) of (10-5 M to 10-7 M) was achieved on a portable Raman device for three common pesticides residues (thiram, fonofos and triadophos) on dendrobium leaves and stem according to the molecular fingerprint, indicating its excellent in-situ detection capability. Further, the multiplex detection ability of the Ag/PDMS film is also demonstrated by analyzing the mixture of four typical analytes. Benefiting from its high signal uniformity, this flexible Ag/PDMS substrate also showed good quantitative detection capabilities.

DOMe: A deduplication optimization method for the NewSQL database backups.

Reducing duplicated data of database backups is an important application scenario for data deduplication technology. NewSQL is an emerging database system and is now being used more and more widely. NewSQL systems need to improve data reliability by periodically backing up in-memory data, resulting in a lot of duplicated data. The traditional deduplication method is not optimized for the NewSQL server system and cannot take full advantage of hardware resources to optimize deduplication performance. A recent research pointed out that the future NewSQL server will have thousands of CPU cores, large DRAM and huge NVRAM. Therefore, how to utilize these hardware resources to optimize the performance of data deduplication is an important issue. To solve this problem, we propose a deduplication optimization method (DOMe) for NewSQL system backup. To take advantage of the large number of CPU cores in the NewSQL server to optimize deduplication performance, DOMe parallelizes the deduplication method based on the fork-join framework. The fingerprint index, which is the key data structure in the deduplication process, is implemented as pure in-memory hash table, which makes full use of the large DRAM in NewSQL system, eliminating the performance bottleneck problem of fingerprint index existing in traditional deduplication method. The H-store is used as a typical NewSQL database system to implement DOMe method. DOMe is experimentally analyzed by two representative backup data. The experimental results show that: 1) DOMe can reduce the duplicated NewSQL backup data. 2) DOMe significantly improves deduplication performance by parallelizing CDC algorithms. In the case of the theoretical speedup ratio of the server is 20.8, the speedup ratio of DOMe can achieve up to 18; 3) DOMe improved the deduplication throughput by 1.5 times through the pure in-memory index optimization method.

Using shadow page cache to improve isolated drivers performance.

With the advantage of the reusability property of the virtualization technology, users can reuse various types and versions of existing operating systems and drivers in a virtual machine, so as to customize their application environment. In order to prevent users' virtualization environments being impacted by driver faults in virtual machine, Chariot examines the correctness of driver's write operations by the method of combining a driver's write operation capture and a driver's private access control table. However, this method needs to keep the write permission of shadow page table as read-only, so as to capture isolated driver's write operations through page faults, which adversely affect the performance of the driver. Based on delaying setting frequently used shadow pages' write permissions to read-only, this paper proposes an algorithm using shadow page cache to improve the performance of isolated drivers and carefully study the relationship between the performance of drivers and the size of shadow page cache. Experimental results show that, through the shadow page cache, the performance of isolated drivers can be greatly improved without impacting Chariot's reliability too much.