In this paper, we propose two new approaches for preparing active substrates for surface-enhanced Raman scattering (SERS). In the first approach (method 1), one transfers AgI nanoparticles capped by negatively charged mercaptoacetic acid from a AgI colloid solution onto a quartz slide and then deoxidizes AgI to Ag nanoparticles on the substrate. The second approach (method 2) deoxidizes AgI to Ag nanoparticles in a colloid solution and then transfers the Ag nanoparticles capped by negatively charged mercaptoacetic acid onto a quartz slide. By transfer of the AgI/Ag nanoparticles from the colloid solutions to the solid substrates, the problem of instability of the colloid solutions can largely be overcome. The films thus prepared by both approaches retain the merits of metal colloid solutions while they discharge their shortcomings. Accordingly, the obtained Ag particle films are very suitable as SERS active substrates. SERS active substrates with different coverages can be formed in a layer-by-layer electrostatic assembly by exposing positively charged surfaces to the colloid solutions containing oppositely charged AgI/Ag nanoparticles. The SERS active substrates fabricated by the two novel methods have been characterized by means of atomic force microscopy (AFM) and ultraviolet−visible (UV−vis) spectroscopy. The results of AFM and UV−vis spectroscopy show that the Ag nanoparticles grow with the increase in the number of coverage and that most of them remain isolated even at high coverages. Consequently, the surface optical properties are dominated by the absorption due to the isolated Ag nanoparticles. The relationship between SERS intensity and surface morphology of the new active substrates has been investigated for Rhodamine 6G (R6G) adsorbed on them. It has been found that the SERS enhancement depends on the size and aggregation of the Ag particles on the substrates. Especially, we can obtain a stronger SERS signal from the substrate prepared by method 1, implying that for the metal nanoparticles capped with stabilizer molecules such as mercaptoacetic acid, the in situ deoxidization in the film is of great use in preparing SERS active substrates. Furthermore, we have found that the addition of Cl- into the AgI colloid solution changes the surface morphology of the SERS active substrates and favors stronger SERS enhancement.

Mercaptoacetic acid-capped spherical silver nanoparticles with a diameter of about 17 nm were prepared by a simple chemical reaction. The formation process of the silver nanoparticles was investigated by UV-visible (UV-vis) spectroscopy and transmission electron microscopy. The results show that the spherical and rodlike particles were formed at the beginning of the reaction, and then the rodlike particles were gradually converted into spherical particles with the reaction continuing. Finally, the content of the rodlike particles was less than 3% in the silver colloid. Thus, the final obtained silver nanoparticles were uniform in their shapes and showed little variation in their sizes. This silver colloid can remain stable for several weeks, which makes it convenient for use in practice. We also investigated the effect of Clon the rate of changes in the optical properties of the silver colloid by UV-vis absorption. The results indicate that Claccelerates the aggregation of the colloidal particles by effectively screening the repulsive electrostatic interactions between the negatively charged silver particles. We used the self-assembled technique to transfer the silver nanoparticles onto solid substrates from the colloid with and without Clin the solution. The UV-vis spectra show that the absorption band red shifts and a new band appears at a longer wavelength when the silver nanoparticles are transferred onto the substrate from the colloid with Clin the solution, indicating that the silver nanoparticles can grow and aggregate on the substrate. This was further confirmed by the atomic force microscopy measurements. Both the silver colloid and the substrates prepared by transferring the silver nanoparticles from the silver colloidal solution onto the quartz slides can serve as surface-enhanced Raman spectroscopy (SERS)-active substrates. It was found that the SERS enhancement depends on the sizes and aggregation of the silver particles, and the addition of Clgenerates much stronger SERS signals.

Soybean lines, each containing a different resistance gene (Rps), are used as differentials to characterize isolates of Phytophthora sojae as physiologic races. Surveys in different soybean production regions have used various sets of soybean differentials thought to carry the same Rps genes. In some instances, isolates of P. sojae have been reported to have different reactions when evaluated in labs using different sets of differentials that were believed to have the same Rps gene. The objective of this study was to compare the consistency of racial classification when three different sets of soybean differentials were challenged with a common set of five races of P. sojae from Ohio and Indiana. Three soybean differential sets (USDA Soybean Germplasm Collection, The Ohio State University, and USDA-ARS Purdue University) were challenged with P. sojae using the hypocotyl inoculation test at OSU and USDA-ARS Purdue. Isolates of races 1, 3, 4, 7, and 25 from Ohio and Indiana had the same reaction on all three sets of soybean differentials for Rps1b, Rps1c, Rps1k, Rps3a, Rps3b, Rps3c, Rps6, Rps7, and on differentials Harlon, Harosoy 12xx, L59-731, and Union for Rps1a. L88-8470 used as a differential for Rps1a and L93-3312 used for Rps1d did not have the expected response. Isolates of races 4 and 25 from Ohio and Indiana responded differently on differentials with the Rps2 gene because this gene was not used previously to characterize races of P. sojae. A similar reaction occurred when differentials with Rps4 and Rps5 were inoculated with isolates of races 1 and 7, respectively. A standardized set of soybean differentials, corresponding to different maturity groups, for thirteen of the fourteen Rps genes is recommended. Accepted for publication 5 February 2004. Published 9 March 2004.

We report that 3 nm diameter CdTe quantum dots can generate enhanced Raman scattering. The Raman signal of 4-mercaptopyridine (4-Mpy) adsorbed on CdTe quantum dots shows a 104 enhancement compared with that of bulk 4-Mpy. The enhanced phenomenon based on CdTe quantum dots also provides new insight to help understand the enhancement mechanism. A charge-transfer mechanism is most likely responsible for the observed enhancement, since plasmon resonances are ruled out. This study points to the possibility of using quantum dots, with chemisorption in some important practical systems, such as the application of quantum dots as nanosized building blocks and markers in biological imaging.

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BackgroundColorectal cancer (CRC) is one of the most common malignant tumors in the world. Ferroptosis is a newly defined form of cell death, distinguished by different morphology, biochemistry, and genetics, and involved in CRC progression and treatment. This study aims to establish a predictive model to elucidate the relationship between ferroptosis and prognosis of CRC patients, to explore the potential value of ferroptosis in therapeutic options.MethodsThe ferroptosis-related genes were obtained from the GeneCards and FerrDb websites. The limma R package was used to screen the differential ferroptosis-related genes (DEGs) in CRC from The Cancer Genome Atlas (TCGA) dataset. The least absolute shrinkage and selection operator (LASSO) and multivariate Cox regressions were to establish the 10-gene prognostic signature. The survival and receiver operating characteristic (ROC) curves were illustrated to evaluate the predictive effect of the signature. Besides, independent prognostic factors, downstream functional enrichment, drug sensitivity, somatic mutation status, and immune feature were analyzed. Moreover, all these conclusions were verified by using multiple datasets in International Cancer Genome Consortium (ICGC) and Gene Expression Omnibus (GEO).ResultsTen ferroptosis-related gene signature (TFAP2C, SLC39A8, NOS2, HAMP, GDF15, FDFT1, CDKN2A, ALOX12, AKR1C1, ATP6V1G2) was established to predict the prognosis of CRC patients by Lasso cox analysis, demonstrating a good performance on Receiver operating characteristic (ROC) and Kaplan–Meier (K–M) analyses. The CRC patients in the high- or low-risk group showed significantly different fractions of immune cells, such as macrophage cells and CD8+ T cells. Drug sensitivity and somatic mutation status like TP53 were also closely associated with the risk scores.ConclusionsIn this study, we identified a novel ferroptosis-related 10-gene signature, which could effectively predict the prognosis and survival time of CRC patients, and provide meaningful clinical implications for targeted therapy or immunotherapy. Targeting ferroptosis is a good therapeutic option for CRC patients. Further studies are needed to reveal the underlying mechanisms of ferroptosis in CRC.