Papers by Keyword: SPR

Abstract: The determination of glucose concentrations in the blood and urine were important to monitor the health of human being. This study was carried out to study the effect GO thicknesses in enhancing the sensitivity of the Au/GO sensor for detection of glucose with various concentration. The partial unclad SMF was fabricated by using low-cost mechanical etching technique. The cladding thickness was successfully reduced from 125μm to 124μm by using this technique. To enhance the strength of evanescent field, Au nanoparticles were deposited on top of unclad fiber via drop casting method. To excite surface plasmon polaritons. GO with various layers from one to five layers were coated on the Au coated partial unclad SMF. The optimum sensitivity of the Au/GO SMF was resulted as three layers of GO with laser excitation under infrared range, λ=1310nm was employed. In conclusion, the effect of GO thicknesses mainly influenced the performance of the proposed sensor, in which the best thickness of GO to enhance the evanescent field and the excitation of SPP is three layers.

Abstract: Gold nanoparticles (AuNPs) have been successfully synthesized using aqueous sambiloto (Andrographis Paniculata Ness) leaf extract as a reducing agent. This method of synthesizing nanoparticles is called biosynthesis. Characterization was carried out using various techniques including UV-Vis, FTIR, and TEM. The results showed that the optimal synthesis ratio, i.e., AuCl₃ solution : sambiloto leaf extract, was 30 µl : 10 ml with a synthesis rate of 0.159 a.u./h. The characteristic of the gold nanoparticles synthesized is that the surface Plasmon resonance (SPR) wavelength is 529.00 nm; it was stable after 4 hours of synthesis and stayed until 24 hours at an SPR wavelength of 527.00-531.50 nm. The functional groups formed include O-H, aliphatic C-H, C=O stretch, aromatic C=C stretch, and C-O stretch. The size of the nanoparticles is in the range of 1-20 nm.

Abstract: Monodispersed Ag nanorods were synthesized using a one-pot synthesis method. These Ag nanorods normally manifest dual surface plasmon resonance (SPR) peaks. This work presents a study of the variation of SPR peaks with variation in the shape of Ag nanorods. Shape variation was achieved through the degradation of a shape-controlling agent (PVP in this work) under white light irradiance with silica passivation to halt further shape variations. This paper also reports the growth & characterization of thin films of the synthesized rod-shaped silver nanoparticles on glass slides along with studies on band pass filter characteristics of the as-synthesized nanoparticles.

Abstract: Autonomous Guided Vehicles (AGV) have the ability to operate on their own, perform tasks without human intervention. However, the investment cost is very high, so it is not suitable for countries with cheap workers like Vietnam. Therefore, this article will aim to build a complete AGV model that can move to the given coordinates. Model of AGV is 6-wheeled vehicles driven by 4 engines with the advantage of good movement in soft terrain, subsidence, ruggedness, slope, easy to balance and limit the vibration. Furthermore, we propose a method to improve the quality of the traditional A* algorithm by eliminating unnecessary intermediate points, which is Shortcut Path Reduction (SPR). Experimental results show that the vehicle can perform the bending technique, following straight lines and broken lines. Besides, the SPR not only met the requirements but also reduced the length of the journey.

Abstract: Enhancement in plasmonic response of metal nanoparticles in the form of metal/metal oxide nanocomposites is very interesting from both the theoretical understanding and application. Metal based oxide/Ag nanocomposites were synthesized by polyol process. Metal oxide nanoparticles present in nanocomposites as core and noble metal as a shell are of interest in investigation of plasmonic behavior of noble metals and sensing application. Cobalt ferrite (CoFe₂O₄) and ZnO were used as oxide core in the form of spherical and rod nanostructures respectively. Presence of Ag was confirmed by XRD and SEM analysis. In this paper we summarize the synthesis and characterization of plasmonic properties of composite nanostructures. Optical absorption studies performed on CoFe₂O₄@Ag and ZnO@Ag exhibit sharp plasmonic resonance but shifted towards lower wavelength (blue shift). An attempt has been made to explain this shift using the Mie scattering calculations based on size variation and change in the dielectric of the surrounding medium.

Abstract: Performance of modular surface plasmon resonance (mSPR) sensor based on refractive index is discussed in this paper. The sensor was built in house using a polychromatic light source, polarizer to produce a transverse magnetic wave, high refractive index waveguide, gold-coated disk, single channel cell and spectrometer for data analysis. A knob for adjusting the angle of the incident provides a means for ease of angle variation which simplifies the design of the instrument for portability purposes. In conventional SPR, the light source need to be delocalized for search of the resonance angle, making the instrument bulky in size and had to be laboratory-based. The efficiency of the newly designed SPR biosensor was tested using a various percentages of ethanol in deionized water. Observations on the shifts of the resonance wavelength with ethanol strength revealed that the SPR biosensor has a sensitivity of 64 nm/RIU and a resolution of ~10² RIU.

Abstract: The demand for tunable surface plasmon (SP) of embedded metal nanoparticles (NPs) in rare earth doped inorganic lasing glasses is ever-growing. Following melt quenching method Er³⁺ doped zinc-boro-tellurite glasses containing silver (Ag) NPs are prepared. Glasses are heat treated (thermally annealed) at varying temperatures and time duration to alter the NPs morphology which generates SP. The annealing assisted SP resonance mediated modification in spectral features is discerned. Samples heat treatment at 410 °C for 6 hrs duration ensures the reduction of Ag+ ions to Ag^o NPs. Thermally annealed glasses are characterized via XRD, UV–Vis-IR absorption, photoluminescence spectroscopy, and TEM imaging. XRD spectra confirm the amorphous nature of the glass and TEM image reveals the existence of homogeneously distributed spherically shaped silver NPs of average diameter ~4.5 nm. NPs are found to grow with the increase of both annealing time and temperature. The UV–Vis spectra exhibit seven absorption bands corresponding to 4f–4f transitions of Er³⁺ ions in the wavelength range of 500-650 nm. The localized SPR band is evidenced at 550 and 580 nm. Heat treatment causes a red shift of the plasmon peaks ascribed to the alteration in glass refractive index. Furthermore, the glass sample annealed for 6 hrs displays maximum enhancement in the emission intensity corresponding to the peaks centered at 536 (²H_11/2→⁴I_15/2), 550 (⁴S_3/2→⁴I_15/2) and 632 nm (⁴F_9/2→⁴I_15/2). This enhancement is primarily attributed to the local field effect of the silver NPs. Admirable features of the results suggest that our systematic method for heat treatment in tuning NPs size assisted SPR may contribute towards the development of functional glass.

Abstract: Optimizing of the spectroscopic features of rare earth (RE) doped inorganic glasses via tuneable growth of metallic nanoparticles (NPs) is demanding in plasmonic based nanophotonics. We report the gold (Au) NPs assisted sizeable enhancements in Er³⁺ luminescence in zinc-sodium tellurite glass. Glasses of the form 70TeO₂-20ZnO-10Na₂O-(x)Er₂O₃-(y)Au (x = 0.0 and 1.0 mol%; y = 0.0-0.6 mol% in excess) are synthesized via melt-quenching method and thoroughly characterized. Au concentration dependent variations in the physical and spectroscopic properties of glasses are determined. XRD data confirms the amorphous nature of all samples. UV-Vis-NIR spectra reveal seven absorption bands corresponding to the transitions from ground state (⁴I_15/2) to ⁴I_13/2, ⁴I_11/2, ⁴I_9/2, ⁴F_9/2, ²H_11/2, ⁴F_7/2 and ⁴F_5/2 excited states of Er³⁺. TEM micrograph manifests the existence of non-spherical Au NPs with average size of 8.6 nm. Prominent surface plasmon band of Au NPs is evidenced around 629 nm. Furthermore, Au NPs display a SPR mediated strong absorption in the visible region. Room temperature visible down-conversion emission (under 425 nm excitation) reveal three significant peaks centred at 532 (moderate green represent ²H_11/2 → ⁴I_15/2 transition), 550 (weak green represent ⁴S_3/2 → ⁴I_15/2 transition) and 588 nm (strong green represent ⁴S_3/2 → ⁴I_15/2 transition). Glass containing 0.4 mol% of Au exhibiting the highest luminescence intensity is ascribed to the NPs local field enhancement and energy transfer between RE ions and NPs. Variations in the physical properties of glass are explained in terms of the alteration in structures and ligand interactions with Au NPs present in the glass network. The intense field amplification discerned in the vicinity of Au NPs is attributed to the charge accumulation at the surface of the NPs. Surface plasmon resonance (SPR) of Au NPs and energy transfer (ET) from NPs to Er³⁺ ions are primarily attributed for the observed spectral modification. It is established that our glass composition displaying such significant enhancement may be beneficial for the development of up-converted solid state lasers and other plasmonic devices.

Abstract: A system to monitor the signal produced by surface plasmon resonance (SPR) has been designed and tested. The built-in sensor consists of a polarized light source having a wave length 840 nm and a built in 128 photodiodes constructed around the maximum SPR angle to detect the reflection light from the gold surface. The signal produced from the diodes is then amplified and digitized. We use 5173 Hz clock to sample the signal generated by the diode array pixel during the reflection process producing SPR signal around the maximum angle. We program Arduino Mega 2560 to process the signals and transfer it using Lab View to present the data versus sampling time. Doing this, we can record the SPR signal versus time, known as the SPR dynamic signal. To test the performance of the system and to know the properties of the SPR signal, we test the system using ethyl alcohol with concentration of 10% (v/v) up to 90% (v/v). The result shows that the system can be used to monitor the dynamics of SPR signal during the reaction process and it indicates the possibility of using the instrument to detect various kinds of SPR signal related to the chemical and or biological process in the samples.

Abstract: This paper deals with a new invention of modular surface plasmon resonance (SPR) biosensor device based on wavelength modulation wherein the angle of incidence of the light source is fixed and the shift in wavelength at resonance is monitored. This device is capable of detecting biomolecular binding interactions of different species such as protein and viruses based on changes in the refractive index of the dielectric environment. White light source mounted with a polarizer is used to excite plasmons on the sensor surface which is thin gold film of ~21 μm thickness coated on BK-7 glass. A variable angle reflection sampling system (VARSS) device from Ocean Optics was modified to incorporate the transducer components and sampling accessories. SPR was observed at the angle of incidence of the light fixed at 29°. At this point, plasmon evanescent wave coupling occurred with highest loss of light intensity. HR4000-UV-NIR photodetector is used to observe the change in resonance wavelength when the dielectric environment around the surface of the transducer was changed. Two liquid samples; water (n=1.33) and ethylene glycol (n=1.43) was introduced onto the sensor surface to model changes in wavelength resonance with difference in refractive index of dielectric environment. It was observed that the resonance wavelength for water and ethylene glycol are 590.10 nm and 594.23 nm respectively when reference to air (n=1.00) indicating the workability of the device.