AuAg alloy film-based colorful SPR imaging sensor for highly sensitive immunodetection of benzo[a]pyrene in water

Flexible hyperspectral surface plasmon resonance microscopy

Optical techniques for visualization and quantification of chemical and biological analytes are always highly desirable. Here we show a hyperspectral surface plasmon resonance microscopy (HSPRM) system that uses a hyperspectral microscope to analyze the selected area of SPR image produced by a prism-based spectral SPR sensor. The HSPRM system enables monochromatic and polychromatic SPR imaging and single-pixel spectral SPR sensing, as well as two-dimensional quantification of thin films with the measured resonance-wavelength images. We performed pixel-by-pixel calibration of the incident angle to remove pixel-to-pixel differences in SPR sensitivity, and demonstrated the HSPRM's capabilities by using it to quantify monolayer graphene thickness distribution, inhomogeneous protein adsorption and single-cell adhesion. The HSPRM system has a wide spectral range from 400 nm to 1000 nm, an optional field of view from 0.884 mm² to 0.003 mm² and a high lateral resolution of 1.2 μm, demonstrating an innovative breakthrough in SPR sensor technology.

On the Aromatic Stabilization of Fused Polycyclic Aromatic Hydrocarbons

The thermodynamic properties and band gap energies were evaluated for six ortho- and peri-fused polycyclic aromatic hydrocarbons (PAHs): triphenylene; benzo[a]pyrene; benzo[e]pyrene; perylene; benzo[ghi]perylene; coronene. The standard molar enthalpies of formation in the crystalline state and the standard molar enthalpies of sublimation were measured by high precision combustion calorimetry and Knudsen effusion methodology, respectively. The combination of the molar enthalpies of formation in the crystalline state with the respective enthalpies of sublimation was used to evaluate the energetics of the progressive peri-fusion of the aromatic moieties from triphenylene to coronene aiming to investigate the hypothetical superaromaticity character of coronene. The linear trend of the enthalpy of formation in crystalline and gaseous phases in the series (from benzo[e]pyrene to coronene) is an irrefutable indication of a non-superaromaticity character of coronene. High accurate thermodynamic properties of sublimation (volatility, enthalpy, and entropy of sublimation) were derived by the measurement of vapor pressures as a function of temperature, using a Knudsen/quartz crystal effusion methodology. Furthermore, the π-electronic conjugation of these compounds was explored by evaluation of the optical band gaps along with this series of compounds. The morphology of perylene, benzo[ghi]perylene, and coronene thin films, deposited by physical vapor deposition onto transparent conductive oxide substrates (ITO and FTO), was used to analyze the nucleation and growth mechanisms. The morphologies observed were found to be related to the cohesive energy and entropy of the bulk.

Combined SPRi Sensor for Simultaneous Detection of Nitrate and Ammonium in Wastewater

Water pollution is a serious problem in modern society. Agriculture, being responsible for the discharge of agrochemicals, organic matter, or drug residues, produces a huge amount of wastewater. Aquaponics has the potential to reduce both water consumption and the impact of water pollution on fish farming and plant production. In the aquatic environment, inorganic nitrogen is mostly present in the form of nitrate and ammonium ions. Nitrate, as a final product of ammonia mineralization, is the most common chemical contaminant in aquifers around the world. For continuous monitoring of nitrogen compounds in wastewater, we propose a sensor for the simultaneous detection of nitrate and ammonium. A surface plasmon resonance imaging method with enzyme-mediated detection was used. Active layers of nitrate reductase and glutamine synthetase were created on the gold surface of a biochip and tested for the sensing of nitrate and ammonium in water from an aquaponic system. The proposed sensor was applied in water samples with a concentration of NO3- and NH4+ in a range between 24-780 mg·L-1 and 0.26-120 mg·L-1, respectively, with minimal pretreatment of a sample by its dilution with a buffer prior to contact on a biochip surface.

Fabrication of a mesoporous silica film based optical waveguide sensor for detection of small molecules

In this paper, a thick mesoporous silica film (MSF) (more than 700 nm) was fabricated via the two-step enhancing Stöber solution growth approach (ESSGA). According to the optimization based on the transfer matrix method, a thicker MSF sensor has higher waveguide index sensitivity and is more suitable for the adsorbent detection, while a thinner MSF sensor has higher covered medium index sensitivity and is more appropriate for non-adsorbent detection. The covered medium index sensitivity and refractive index resolution of the fabricated MSF optical waveguide sensor were calculated to be 53.18 deg/RIU and ${1.28}\; \times \;{{10}^{ - 6}}\;{\rm RIU}$1.28×10^-6RIU, respectively. For the detection of a small molecule, hexadecyltrimethylammonium bromide was used as a model of a small molecule to verify its sensing property and its limit of detection (LOD) as low as 1.879 nM was obtained. In order to detect heavy metal ions, the MSF was modified with an amino group by the post-grafted method. The response of the resonance angle shift is more sensitive to ${{\rm Pb}^{2 + }}$Pb²⁺ ion than ${{\rm Cu}^{2 + }}$Cu²⁺ ion and both their LODs could reach the nanomolar detection level; those are 17.30 and 6.44 nM, respectively.