The localized surface plasmon resonance (LSPR) due to light–particle interaction and its dependence on the surrounding medium have been widely manipulated for sensing applications. The sensing efficiency is governed by the refractive index-based sensitivity (${\eta }_{RIS}$) and the full width half maximum (FWHM) of the LSPR spectra. Thereby, a sensor with high precision must possess both requisites: an effective ${\eta }_{RIS}$ and a narrow FWHM of plasmon spectrum. Moreover, complex nanostructures are used for molecular sensing applications due to their good ${\eta }_{RIS}$ values but without considering the wide-band nature of the LSPR spectrum, which decreases the detection limit of the plasmonic sensor. In this article, a novel, facile and label-free solution-based LSPR immunosensor was elaborated based upon LSPR features such as extinction spectrum and localized field enhancement. We used a 3D full-wave field analysis to evaluate the optical properties and to optimize the appropriate size of spherical-shaped gold nanoparticles (Au NPs). We found a change in Au NPs’ radius from 5 nm to 50 nm, and an increase in spectral resonance peak depicted as a red-shift from 520 nm to 552 nm. Using this fact, important parameters that can be attributed to the LSPR sensor performance, namely the molecular sensitivity, FWHM, ${\eta }_{RIS}$, and figure of merit (FoM), were evaluated. Moreover, computational simulations were used to assess the optimized size (radius = 30 nm) of Au NPs with high FoM (2.3) and sharp FWHM (44 nm). On the evaluation of the platform as a label-free molecular sensor, Campbell’s model was performed, indicating an effective peak shift in the adsorption of the dielectric layer around the Au NP surface. For practical realization, we present an LSPR sensor platform for the identification of dengue NS1 antigens. The results present the system’s ability to identify dengue NS1 antigen concentrations with the limit of quantification measured to be 0.07 μg/mL (1.50 nM), evidence that the optimization approach used for the solution-based LSPR sensor provides a new paradigm for engineering immunosensor platforms.

Owing to the localized plasmon resonance of an ensemble of interacting plasmonic nanoparticles (NPs), there has been a tremendous drive to conceptualize complex optical nanocircuits with versatile functionalities. In comparison to modern research, there is still not a sufficient level of sophistication to treat the nanostructures as lumped circuits that can be adjusted into complex systems on the basis of a metatronic touchstone. Here, we present the design, assembly, and characterization of single relatively complex photonic nanocircuits by accurately positioning several metallic and dielectric nanoparticles acting as modular lumped elements. In this research, Au NPs along with silica NPs were used to compare the proficiency and precision of our lumped circuit model analytically. On increasing the size of an individual Au NP, the spectral peak resonance not only modifies but also causes more scattering efficiency which increases the fringe capacitance linearly and decreases the nanoinductance of lumped circuit element. The NPs-based assembly induced the required spectral resonance ascribed by simple circuit methods and are depicted to be actively reconfigurable by tuning the direction or polarization of input signals. Our work demonstrates a vital step toward developing the modern modular designing tools of complex electronic circuits into nanophotonic-related applications.

X-ray phase-contrast imaging has experienced rapid development over the last few decades, and, in this technology, the phase modulation strategy of phase stepping (PS) is used most widely to measure the sample’s phase signal. However, because of its discontinuous nature, PS has the defects of worse mechanical stability and high exposure dose, which greatly hinder its wide use in dynamic phase measurement and potential clinical applications. We demonstrate preliminary research on the use of integrating-bucket (IB) phase modulation method to retrieve the phase information in grating-based x-ray phase-contrast imaging. Experimental results show that our proposed method can be well employed to extract the differential phase-contrast image, compared with the commonly used PS strategy, the advantage of the IB phase modulation technique is that fast measurement and low dose are promising.

In X-ray grating-based phase contrast imaging, information retrieval is necessary for quantitative research, especially for phase tomography. However, numerous and repetitive processes have to be performed for tomographic reconstruction. In this paper, we report a novel information retrieval method, which enables retrieving phase and absorption information by means of a linear combination of two mutually conjugate images. Thanks to the distributive law of the multiplication as well as the commutative law and associative law of the addition, the information retrieval can be performed after tomographic reconstruction, thus simplifying the information retrieval procedure dramatically. The theoretical model of this method is established in both parallel beam geometry for Talbot interferometer and fan beam geometry for Talbot-Lau interferometer. Numerical experiments are also performed to confirm the feasibility and validity of the proposed method. In addition, we discuss its possibility in cone beam geometry and its advantages compared with other methods. Moreover, this method can also be employed in other differential phase contrast imaging methods, such as diffraction enhanced imaging, non-interferometric imaging, and edge illumination.

<!-- *** Custom HTML *** --> Long exposure time is one of the major limitations in x-ray phase-contrast imaging (XPCI). Therefore, we demonstrate a promising alternative method for grating-based XPCI coupled with cascaded Talbot–Lau interferometers (TLIs). A Fourier analysis of the moiré fringe patterns generated by the interferometers was used to obtain the multicontrast images (such as absorption, differential phase-contrast, and normalized visibility-contrast images) with a single exposure. The cascaded configuration with TLI and inverse TLI using large-period absorption gratings was established to verify the effectiveness of the algorithm and three multicontrast images of a polytetrafluoroethylene (PTFE) tube were obtained experimentally. The groove structures in the PTFE can be clearly identified in the differential phase-contrast image. This method shows potential for application of cascaded TLI in medical imaging.

In this manuscript, a technique for the fast retrieval and dose saving single-shot imaging of X-ray scattering information based on angular signal radiography and the staggered grating is simulated. A staggered grating is used to encode two sample images into a single exposure. Results show that single-shot X-ray scattering imaging, being low dose, can be used for biomedical applications where X-ray absorption-based imaging produces low contrast. Hence, our proposed method can be used towards the development of X-ray scattering imaging based on grating interferometer into practical applications.