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Surface‐enhanced Raman scattering (SERS) spectroscopy has renowned its fame for the ultra‐high sensitivity and single‐molecule detection ability, and listed as a fingerprint spectrum representative in various trace detection fields. Considerable efforts have been made by researchers to design high‐sensitive SERS‐active substrates ranging from noble metals to semiconductors. This review summarizes the fundamental theories for SERS technique, that is, the electromagnetic enhancement mechanism and chemical enhancement mechanism and the state‐of‐the‐art design strategies for noble metal and semiconductor substrates. It also sheds light on the effective approaches to improve the SERS activity for noble metal substrates, that is, tuning the localized surface plasmon resonance position, the assembling of hot spots, and precise controlling of nanogaps. Although charge transfer is considered as the main reason for the enhancement mechanism for semiconductors at the present stage, the underlying theoretical basis remains mysterious. This review summarized the critical points for SERS‐active substrates design and prospected the future development direction of SERS technology.

Polyanion-type sodium superionic conductor (NASICON) Na3V2(PO4)2F (NVOPF) is a promising cathode material for sodium ion batteries (SIBs). However, NVOPF shows relatively low specific capacity and ...

In this paper, a photonic crystal fiber sensor is proposed which have four-opening channels that support surface plasmon resonances. By detecting the optical spectrum of leakage from the fiber core to the four regions created on its periphery, the sensitivity of the sensor can be assessed. Gold is used as the plasmonic material in the infrared wavelength range on the Titanium oxide film which is used as a substrate layer to increase the coupling and adhesion. Influences of structural parameters on the sensor performance are investigated by the Finite Difference Element method. Sensitivities for refractive index of 1.34-1.44 for wavelength ranges (690-1500 nm) with maximum wavelength sensitivity of 25,600 nm / RIU and maximum amplitude sensitivity and 7367 ( RIU-1 ) and figure of merit (FOM) of 547 ( RIU-1 ) have been calculated. In addition to high sensitivity, great FOM value of this sensor is an important feature. This sensor can be used to identify chemicals and biomolecules.

A high performance sinusoidal grating-based surface plasmon resonance (SPR) biosensor is proposed. The angular interrogation method has been used to study the performance of the sensor. The sensitivity as well as the width of the SPR curves and reflective amplitude is considered for designing the sensor. Compared with the gold(Au)-based SPR sensor, we find that the silver(Ag)-based sensor has the better performance. Numerical simulations show that the sensitivity of the Ag-based sensor is 193.9°/RIU.

Noble metal nanoparticles (NPs) have been widely explored in surface-enhanced spectroscopies (SES) because of their ability to generate intense electric fields originating from the surface plasmon resonances. Particularly, coupled metallic NPs have attracted a lot of attentions in SES because they can generate much higher electric field enhancement than the single ones. In this study, two kinds of coupled structures, the dimer and the metal NP over the metal film (MNOMF), are examined using finite-difference time-domain method. Hot spots in these structures are optimized for high-performance SES. Hot spots in dimers are usually confined within small volumes, limiting the sensitivity and reproducibility of SES. In this study, we show that Au spiky NP dimers (SNPDs) can provide large-volume hot spots, arising from the synergistic effect of “lightning rod effect” in spiky NPs and the interparticle coupling. The “hot spots volume” (defined as the whole volumes of all the regions with electric field enhancement larger than 1E4) in T–T SNPD is almost 5 times and 7 times larger than in the sphere dimer and spike dimer with the same 2 nm gap, respectively. In addition, further increased “hot spots volume” is achieved in crossed T–T SNPD, being ~1.5 times of that in T–T SNPD. At the same time, the electric field enhancement (|E|^2/|E0|^2) in the tip-to-tip (T–T) SNPD with a 2 nm gap is as large as 1.21E6. The results indicate a strategy to obtain huge-volume hot spots with large electric field enhancement in dimers by adding a bulky core at one end of the spindly building blocks. We have shown SNPDs could provide hot spots with large volumes. Nevertheless, it is hard to fabricate SNPDs in experiments. Alternatively, spiky disk dimers (SDDs) on glass substrate may be fabricated using top-down lithography. We demonstrate crossed T-T SDD can generate much larger “hot spots volume” and much higher electric field enhancement than disk dimer. The results demonstrate the possibility to achieve large-volume hot spots in experiments. In both SNPDs and SDDs, two adjacent particles are coupled in lateral direction. In experiments, it is difficult to achieve precisely controlled small gaps in dimers along lateral direction and hence limiting the enhancement of electric fields. On the contrary, MNOMF which offers coupling in vertical direction can provide even sub-1 nm gap, exhibiting great potentials for SES. In this study, we demonstrate a method to optimize the hot spots in MNOMF by exciting the localized surface plasmon resonances (LSPRs) using the surface plasmon polaritons (SPPs). We find the largest electric field enhancement and the highest surface-enhanced fluorescence intensity are obtained when the SPPs of the metal film are excited. The results show that exciting LSPRs using SPPs can generate 1-3 orders higher electric field intensity than direct exciting the LSPRs using incidence from free space. The ultrahigh enhancement is attributed to the strong confinement of the SPP waves in the vertical direction. The drastically intensified electric fields generated from excitation of LSPRs using SPP waves are extremely essential for sensitive refractive index sensing, high-performance SES, and enhancing the efficiency of optoelectronic devices. DOCTOR OF PHILOSOPHY (MSE)

In this paper, first, the surface acoustic wave (SAW) propagation mode and a method of analyzing the propagation property are introduced briefly. Then, typical composite substrate structures that have been developed to obtain high-performance SAW devices are reviewed. Furthermore, the recent results obtained by the author and research colleagues on the propagation and resonance properties of leaky SAW (LSAW) and longitudinal-type LSAW on dissimilar-material bonded structures comprising a LiTaO3 (LT) or LiNbO3 thin plate with a thickness of less than 1 λ (λː wavelength) and a quartz substrate are described. The control of attenuation and the cause of large coupling factor of LSAWs by utilizing layered structures were also discussed. For the bonded 4 inch wafer of 36°YX-LT/AT90°X-quartz with a thin-plate thickness of 0.3 λ, an admittance ratio of 81 dB, a fractional bandwidth of 4.2%, and resonance and antiresonance factors of approximately 1500 with markedly improved properties compared with a single 36°YX-LT substrate were obtained experimentally at 2.2 GHz.

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.

We succeeded in fabrication of a high-performance surface optical coupler for coupling with $5-\mu m$ -MFD high numerical-aperture (HNA) optical fiber. The fabricated device showed the coupling loss of less than 2.4 dB and 0.5-dB-loss-bandwidth of over 220 nm for TE-polarization.

An efficient surface enhanced Raman scattering (SERS) substrate has been developed based on highly ordered arrays of graphene–isolated Au nanoparticle (G/AuNP). By combining the electromagnetic enhancement activity of AuNP arrays and unique physical/chemical properties of graphene, the G/AuNP arrays shows high performance in terms of sensitivity, signal-to-noise ratio and reproducibility. The average enhancement factor obtained from the G/AuNP arrays for rhodamine 6G probe molecules is over 10 7 . The maximum deviations of SERS intensities from 20 positions of a same SERS substrate are in the range of 4.74% to 6.89% and from 20 different substrates in various batches are in the range of 5.67% to 8.37%, 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 250 nM. This work may open up new opportunities in developing the applications of SERS in biomedical diagnostics, biological sensing and other biotechnology.

Nanogaps or sharp protrusions has been proved useful for surface enhanced Raman scatting (SERS) in single-molecule sensing and a low cost method for fabricating SERS active substrate with these naonstructures is very important for practical applications of SERS in clinical or biological area. In this work, PMMA 3D nanostructures with sub-20nm ordered nanogap network and sharp tips are fabricated by high-fidelity replica molding. The morphology, water repellency property and Raman enhancement effect of the 3D nanostructures are characterized by SEM, water contact angle and SERS. The results show that the 3D nanostructure of rocket-like array has higher SERS enhancement factor (EF) than the 3D nanostructure of nano-lawn due to the ordered nanogaps, and both of them change the surface wettability of PMMA from hydrophilic to hydrophobic, especially for the 3D structure of nano-lawn.

This paper describes application of Sc-doped AlN (ScAlN) to wideband SAW devices in the 1 to 3 GHz range. First, it is shown theoretically that large SAW velocity and electromechanical coupling factor are simultaneously achievable when the ScAlN film is combined with a base substrate with extremely high acoustic wave velocities, such as diamond and SiC. Next, SAW delay lines are fabricated on the ScAlN/6H-SiC structure, and reasonable agreement between the theory and experiment is obtained. Finally, one-port SAW resonators are fabricated on the structure, and it is shown that high-performance is achievable in the 1 to 3 GHz range by use of the structure.

Detection of 2,4,6-trinitrotoluene (TNT) is an important environmental, security and health concern for the global community. TNT is a prime constituent of most of the landmines and bombs and is highly toxic and mutagenic. Various military and terrorist activities (e.g., manufacturing, waste discharge, testing and training) have resulted in extensive contamination of soil and ground water by TNT and its derivatives. Consequently, the development and application of new sensing techniques for detection and quantification of TNT has grown steadily over the years. Despite wide variety of analytical techniques, surface plasmon resonance (SPR) based immunosensors received great attention as a promising mean for TNT detection due to their advantages including high sensitivity, selectivity, good versatility and high throughput. This review explores the recent trend and advancements in immunochemical techniques for environmental monitoring and field detection of TNT. The advantages of the surface plasmon resonance as an optical signal transduction and indirect competitive immunoassay as the sensing principle are discussed with special emphasis on our investigations on TNT detection. A brief description on explosives, land-mines and the current detection techniques (bulk and trace detection) is also provided.

A new strategy for achieving high performance SERS was proposed by using the dummy molecular imprinting technique. The obtained core–shell composite can effectively improve the signal-to-noise ratio and the veracity of trace analysis in SERS detection.

This paper demonstrated the application of Surface Enhanced Raman Scattering (SERS) technology on quantitative analysis in hemodialysis system for real time inspection. SERS has already been proved in high accuracy due to the Raman optical fingerprint signal is unique for every different compound. We investigate the use of silver film on nanosphere (AgFON) SERS technology can distinguish the small concentration change in Creatinine and Urea, which are toxicity molecular, and needed to be removed and real time monitored during dialysis process.

In this poster paper, a novel grinding process for replacing conventional surface and creep feed grinding processes is presented. This grinding process allows high removal rates in hard machining with flexibility and a good surface finish at the same time. A peel grinding process is conducted with a high workpiece velocity and a high depth of cut, using a conventional surface grinding machine and an electroplated CBN wheel with a custom shape. To validate the efficiency of this process, the process forces and the surface roughness values have been carried out experimentally.

Acoustic wave devices based on waveguide modes with shear-horizontal polarisation, i. e. Love modes, are very promising for sensor application, especially in liquid environments. They can be used for determination of liquid density and viscosity as well as for chemical sensors. Up to now, several systems have been reported based on standard ST-quartz. Those devices lack temperature stability which is essential for field application. However, appropriate combinations of crystal cut angle and SiO 2 overlay thickness should provide temperature compensation. Thus, different systems based on Y-rot quartz and lithium tantalate plates with SiO 2 waveguiding films have been investigated. Temperature behavior as well as relevant acoustic properties are compiled. It has been proven that numerical calculations yield a very accurate description of the physical device properties. For both cases of material combinations it has been shown that systems are available combining temperature compensation with a high device sensitivity.

Surface-enhanced Raman scattering (SERS) with enormous enhancements has been applied for ultra-sensitive detection in various fields, but the fabrication of large-scale, controllable and cost-effective substrates is a major challenge. We propose a novel fabrication process with a gas-assisted hot embossing process and an anodic aluminum oxide template to obtain the SERS substrate on a 1 × 1 cm polycarbonate film. The SERS spectra of 4-mercaptobenzoic acid (PMBA) on the gold substrate have been measured. The enhancement factors are between 3.99 × 107 and 4.92 × 107, depending on the heights of nanocones, which can be controlled by the embossing temperature and pressure. The simple and inexpensive SERS substrate has potential for wide application in SERS-based sensors.