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Hyperbolic metamaterials (HMMs) have attracted significant attention with regards to applications related to surface plasmon resonance (SPR) because of their heterodyne response induced by the multimode response and the high K-transfer mode (including transmission and dielectric ones) originated from their unique dispersive properties. However, most HMM-based applications related to fiber optic SPR are still at the theoretical simulation stages. This work reports the synthesis of HMMs using Ag and MgF2. The resulting HMMs were used to fabricate an SPR sensor based on D-type plastic optic fibers (D-POFs). The sensor oscillation modes were theoretically analyzed using the effective medium theory and COMSOL. The optimal synthesis conditions were when the metal filling fraction (ρ) and the number of bilayers (Nbi) were equal to 0.5 and 3, respectively. Experiments showed that at the ambient refractive index in the 1.34–1.356 RIU range, the HMMs/D-POF sensor possessed high sensitivity (1875 nm per RIU), excellent linear response (with the correlation coefficient R2 = 0.987), and reproducibility. Our sensor could also detect saccharin and 2, 6-di-tert-butyl-4-methyl phenol antioxidant 264 (BHT), both of which are toxic. Thus, both theoretical and experimental results showed the applicability of this sensor for real-life detection.

Compared to conventional chemical sensors, this paper presented a chemical sensor system with broad selectivity for a variety of molecules without any surface modification. The system consisted of an unmodified graphene foam as sensing element, an electrical resistance time domain detection system and a Support Vector Machine (SVM) identification system. The chemical sensor adopted 3D graphene foam to increase the reaction area and improve the sensitivity for detecting target molecules. The electrical resistance time domain detection system was constructed to record the graphene resistance curve in real time with different molecules. Based on the diverse shapes of the electrical resistance curves, SVM was used to extract features of each resistance curve and discriminate the corresponding molecules via pattern recognition of each resistance curve without any graphene modification. As validation experiments, six kinds of chemical molecules (chloroform, acetone, ether, toluene, ethyl benzene and methanol) have been tested. The discrimination accuracy for each molecule could be above 98% which showed a broad selectivity for a variety of molecules. Furthermore, through theoretical calculation with the first principle, we concluded that different band structures of the graphene caused by different molecules were the mechanism for the graphene chemical sensor system to discriminate chemical molecules with selectivity. This work may present a new strategy for research and application for graphene chemical sensors.

By combining the excellent surface-enhanced Raman scattering (SERS) activity of Ag nanoparticles (AgNPs), the well-separated pyramid arrays of the pyramidal silicon (PSi) and unique physical/chemical properties of molybdenum disulfide (MoS2), the MoS2@AgNPs@PSi substrate shows high performance in terms of sensitivity, uniformity, reproducibility and stability. By using rhodamine 6G (R6G) as probe molecule, the SERS results indicate that the MoS2@AgNPs@PSi substrate is superior to the AgNPs@PSi, AgA@PSi (the second annealing of the AgNPs@PSi) and the MoS2@AgNPs@flat-Si substrate. The MoS2@AgNPs@PSi substrate also shows the reasonable linear response between the Raman intensity and R6G concentration. The maximum deviations of SERS intensities from 20 positions on a same MoS2@AgNPs@PSi substrate and 10 MoS2@AgNPs@PSi substrates in different batches are less than 7.6% and 9%, respectively, revealing the excellent uniformity and reproducibility of the substrate. Besides, the SERS substrate has a good stability, the Raman intensity of the MoS2@AgNPs@PSi substrate only drop by 15% in a month. The corresponding experimental and theoretical results suggest that our proposed MoS2@AgNPs@PSi substrate is expected to offer a new and practical way to accelerate the development of label-free SERS detection.

We proposed a high sensitivity and a high resolution surface plasmon resonance sensor composed of graphene–WS2 hybrid nanostructure and Au–Ag bimetallic-layers film. The bimetallic-layer configuration uses the high sensitivity of gold and the narrow full width at half maximum (FWHM) of silver to improve the sensor's sensitivity and resolution respectively. Graphene and WS2 serve as an effective light absorption medium. Once they cover the bimetallic-layer, the sensitivity can be further improved significantly. Graphene–WS2–Au–Ag model shows a higher sensitivity and higher resolution than that of the conventional sensing scheme where pure Au thin film is used. In our paper, we mainly use Fresnel equations and the transfer matrix method (TMM) to study the reflectivity and sensitivity as well as the full width at half maximum (FWHM) of the SPR sensor.

Stretchable sensors are essential and important for the new-type stretchable intelligent electronic devices. Three-dimensional (3D) graphene foams are attractive to increase the sensitivity and stretchability, benefiting from a high specific surface area and mechanical strength. Herein, 3D graphene/nickel particles (Gr–NiP) peasecod foams, which were fabricated using CVD and stamp-transfer processes, are proposed and used for stretchable sensor applications. The existing nickel particles, covered by graphene layers, are useful for the formation of 3D nanostructures and separated from each other for stretchable applications. A stretchability (e) of such Gr–NiP foams of up to 80% can be achieved. A low limit of detection (

We demonstrate graphene oxide (GO)-decorated Ag dendritic nanostructures on a copper substrate for surface enhanced Raman scattering (SERS) applications. The Ag dendrites (AgD) were synthesized through a facile and low-cost galvanic replacement reaction of Ag nitrate solution and copper foils. The AgD/Cu was further decorated with GO by a dip-coating method. The GO-decorated AgD exhibited a much higher SERS activity in terms of sensitivity, signal-to-noise ratio and stability compared with non-decorated AgD, indicating that the GO/AgD/Cu substrates could be potentially useful for highly sensitive molecule detecting applications.

In this paper, we designed a 2D distance and rotation angle plasmon ruler based on Fano resonance of a trimer nanostructure, which consists of a concentric square nanoring–disk and an outside nanorod (CSRDR). The Fano dip energy and depth are fairly sensitive to the nanometer-scale displacements and rotations, when the nanodisk moves in all direction and rotates around its center. When the symmetry of the nanoring is broken, we can identify the moving and rotating direction of the nanodisk more accurately. We use the CSRDR nanostructure which supports a narrow line-width as a 2D plasmon ruler, which can enhance the sensitivity of a plasmon ruler significantly.

An efficient surface enhanced Raman scattering (SERS) substrate of graphene-isolated Ag nanoparticle (G/AgNP) has been developed by using excimer laser to ablate the ordered pyrolytic graphite in high vacuum onto Ag nanoparticles. By combining the electromagnetic activity of AgNPs and unique physical/chemical properties of graphene, the G/AgNP substrates shows high performance in terms of sensitivity, signal-to-noise ratio and reproducibility. The average enhancement factor obtained from the G/AgNP substrates for rhodamine 6G probe molecules is over 108. The maximum deviations of SERS intensities from 20 positions of a same SERS substrate are in the range of 4.20% to 6.75% and from 20 different substrates in various batches are in the range of 4.43% to 7.71%, depending on different vibration modes. As a practical application of this SERS system, we detect the adenosine concentration in human serum. The detection results show a good linear correlation between SERS intensity and adenosine concentration within the range of 2 to 200 nM. This work may open up new opportunities in developing the applications of SERS in biomedical diagnostics, biological sensing and other biotechnology.

In our work, we directly synthesized few layer MoS2 on a pyramid-Si substrate to fabricate a surface-enhanced Raman scattering (SERS) substrate via thermally decomposing the precursor of ammonium thiomolybdate ((NH4)2MoS4). Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectra are employed to characterize the as-grown MoS2 layers. Adenosine and cytidine were selected as the probe molecules to investigate the SERS ability of the MoS2-pyramid-Si substrate, and have shown that the MoS2-pyramid-Si substrate can prominently suppress photobleaching and fluorescence of the probe molecule. Compared with the MoS2-flat-Si substrate (MoS2 layers synthesized on flat-Si substrate), the MoS2-pyramid-Si substrate has more significant SERS ability. The minimum detected concentration of both adenosine and cytidine on the MoS2-pyramid-Si substrate can reach 10−6 M. Importantly, the linear relationship between the Raman intensity and the concentration of adenosine or cytidine can apply to the bimolecular detection. This work may provide a new opportunity for the study of the chemistry mechanism (CM) and novel SERS substrate fabrication.

We report a hybrid structure employing two-dimensional graphene and networks of one-dimensional silver nanowires as transparent and flexible electrodes. The hybrid films have sheet resistances as low as ~16 Ω □−1 with a high transmittance of 91.1% at 550 nm, and exhibit impressive stability against oxidation and mechanical flexibility. These properties are superior to commercial transparent electrodes such as indium tin oxides and comparable to the best reported results in transparent electrodes. The hybrid films were successfully applied as transparent and flexible electrodes in acoustic devices that show a high sound pressure level, demonstrating their potential applications for a wide range of optoelectronic and photovoltaic devices.