A facile paper-based chromatography coupled Au nanodendrite on nickel foam for application in separation and SERS measurement.

A simple paper-based chromatography coupling with nickel foam decorated Au nanodendrite (PP-AuND/NiF) was fabricated for simultaneous separation and surface-enhanced Raman scattering (SERS) detection of Rhodamine-6G (R6G) from a mixture of analytes. The three-dimensional porous nickel foam (NiF) was employed as a sampling diffusion platform, and AuND with a high surface active area beneficial for SERS efficiency was electro-deposited directly onto the NiF frame. The structure of AuND/NiF was characterized by X-ray diffraction and scanning electron microscopy. The AuND/NiF could detect R6G at 0.1 nM, and the enhancement factor was 1.84 x 106. The AuND/NiF was durable, with a slight signal decrease after 6 m of drop-testing. Also, upon three days of exposure to ambient air, the signal droped only 3.35 %. Subsequently, the PP-AuND/NiF was constructed by directly situating AuND/NiF on a paper strip, serving as a sample in and out to AuND/NiF. A mixture of two SERS active compounds, namely 2-Naphthalenethiol (2-NpSH) and Rhodamine 6G (R6G), was prepared in ethanol: water (1:1) solution to evaluate PP-AuND/NiF separation capability. Raman measurements along different distances of AuND/NiF were performed, and the signal of 2-NpSH was dismissed after 3.0 mm, while R6G's signals were observed throughout AuND/NiF. In general, the PP-AuND/NiF demonstrated effective separation and SERS measurement of analytes in a mixture, which could be applicable for more complex samples in the future, especially in clinical analysis.

Ambient air monitoring around the dioxin remediation site in Da Nang, Vietnam, using passive air samplers.

The concentrations and temporal variations of polychlorodibenzo-p-dioxins and polychlorodibenzofurans (PCDDs/PCDFs) in ambient air between March 2013 and February 2017 were investigated by passive air samplers containing polyurethane foam (PUF) disks in the dioxin remediation area using in-pile thermal desorption (IPTD) technology at Da Nang airport, Vietnam. The PCDD/PCDF concentrations in ambient air at each site depended on the location of the emission sources and the wind direction, the dioxin contamination level of excavated materials, the periods of excavation and transport, and the operation of the IPTD treatment system. The PCDD/PCDF concentrations were the highest in the former Agent Orange mixing and loading area (AOMLA), which was the closest to the IPTD system, with total toxic equivalent (TEQ) values ranging from 0.437 to 15.3 pg/PUF/day. The total TEQ concentrations in the Sen Lake area ranged from 0.138 to 2.41 pg/PUF/day. The lowest concentration of PCDDs/PCDFs occurred in the northern perimeter area, with total TEQ values ranging from 0.164 to 0.972 pg/PUF/day. The decreasing trend of the PCDD/PCDF concentrations in ambient air was confirmed over time at all three monitoring sites, among which there was a strong decrease in the former AOMLA after February 2015. Residents living near the Da Nang airport were at a low risk of being exposed to PCDDs/PCDFs through inhalation during remediation project implementation, while residents living close to the former AOMLA faced elevated risks with an average daily dose of PCDDs/PCDFs through inhalation ranging from 0.017 to 0.82 pg TEQ/kg body weight/day.

Confocal microwave imaging for breast cancer detection: delay-multiply-and-sum image reconstruction algorithm.

A new image reconstruction algorithm, termed as delay-multiply-and-sum (DMAS), for breast cancer detection using an ultra-wideband confocal microwave imaging technique is proposed. In DMAS algorithm, the backscattered signals received from numerical breast phantoms simulated using the finite-difference time-domain method are time shifted, multiplied in pair, and the products are summed to form a synthetic focal point. The effectiveness of the DMAS algorithm is shown by applying it to backscattered signals received from a variety of numerical breast phantoms. The reconstructed images illustrate improvement in identification of embedded malignant tumors over the delay-and-sum algorithm. Successful detection and localization of tumors as small as 2 mm in diameter are also demonstrated.