ABSTRACT
Combination of high quality cavity such as glass microsphere and emitting nano-particle coating layers can create novel strongly emitting devices. Herein, we demonstrate an erbium-doped silica microsphere coated by dual-emission carbon quantum dots, which have the sizes of 3-5 nm, emitting green up-conversion with narrow line-width green light at wavelength of 537 nm. The dual-emission carbon quantum dots fabricated by hydrothermal process and have luminescent emission wavelengths in the range of 410-550 nm. The carbon quantum dot coated erbium silica microsphere is pumped at wavelength of 976 nm through the optical fibre on which microsphere attached on the tip. The dual-emission carbon quantum dot layers attributed to the strong green up-conversion light enhancement similar coated noble metallic thin films, however the light enhancement from dual-emission carbon quantum dot coated erbium silica microsphere depended on the thickness of coating layers. This result is useful for making visible emitting micro-devices and photonic integrated circuits.
ABSTRACT
In this work, we present a novel fabrication method for making the surface-enhanced Raman scattering (SERS) probe based on silver (Ag) nano-dendrites which are grown and deposited on the end of multi-mode fibre core by a simple and low-cost laser-induced technique. The morphology of the Ag-nanoparticles (AgNPs) could be controlled by the experimental conditions such as laser power, illumination time, and concentration of the reaction solution. The morphology and chemical composition of SERS fibre probes are characterized by high-resolution scanning electron microscope (HR-SEM) and Energy dispersive X-ray spectroscopy (EDX), respectively. These results confirmed how the Ag nanostructures morphology is modified as a function of illumination time of laser irradiation, and the growth and deposition of Ag nanostructures occur only in the main laser-irradiated part on the end of multi-mode fibre core. The achieved SERS-activity substrates on the fibre probes are testing with the detection of low concentration of Rhodamine 6G aqueous solutions in the range of 10-5-10-10 M. This study shows that SERS activity coupled with Ag nano-dendrites substrate on the fibre probe has the best enhancement factor of 1.93×107 for Rhodamine 6G due to the creation of many of hot-spots for amplifying Raman signals by Ag nano-dendrite structures, which is a promising candidate with low-cost SERS probe of chemical compact optical fibre sensors for direct, rapid, real-time and non-destructive detection of chemical compounds in liquid environment.
ABSTRACT
Permethrin, 3-Phenoxybenzyl (1 RS)-cis,trans-3-(2,2-dichlorovinyl)- 2,2-dimethylcyclopropanecarboxylate, has a wide range of applications like insecticide, insect repellent and prevents mosquito-borne diseases, such as dengue fever and malaria in tropical areas. In this work, we develop a prominent monitoring method for the detection of permethrin pesticide using surface-enhanced Raman scattering (SERS) optical fibre substrates. The novel SERS-active optical fibre substrates were grown and deposited silver (Ag) nano-dendrites on the end of multi-mode fibre core by laser-assisted photochemical method. The characteristic of the Ag-nanostructures could be controlled by the experimental conditions, namely, laser illumination time. Ag nanoparticles optical fibre substrates and Ag nano-dendrites optical fibre substrates were prepared with laser illumination time of 3 min and 8 min, respectively. The achieved SERS-activity optical fibre substrates were tested with Rhodamine 6G aqueous solutions. We demonstrate that the SERS activity coupled with Ag nano-dendrites optical fibre substrate has higher Raman enhancement factor due to the creation of many of hot-spots for amplifying Raman signals. Besides, the stability and reproducibility of the Ag nano-dendrites optical fibre substrate were also evaluated with stored time of 1000 hours and relative standard deviation of less than 3%. The Ag nano-dendrite optical fibre substrate was selected for detection of permethrin pesticide in the concentration range of 0.1 ppm-20 ppm with limit of quantification (LOQ) of 0.1 ppm and calculated limit of detection (LOD) of 0.0035 ppm, proving its great potential for direct, rapid detection and monitoring of permethrin.
ABSTRACT
A vast majority of the organic solvents used in industry and laboratories are volatile, hazardous and toxic organic compounds, they are considered as a potent problem for human health and a cause of environmental pollution. Although analytical laboratory methods can determine extremely low solvent concentration, the sensing method with low cost and high sensitivity remains a conundrum. This paper presents and compares three methods (volatile organic compound (VOC), liquid drop and saturated vapour pressure) for determination of organic solvents in a liquid environment by using photonic sensor based on nano-porous silicon (pSi) microcavity structures. Among those, the VOC method provides the highest sensitivity at low solvent volume concentrations because it can create a high vapour pressure of the analyte on the sensor surface owing to the capillary deposition of the organic solvent into the silicon pores. This VOC method consists of three steps: heating the solution with its particular boiling temperature, controlling the flowing gas through liquid and cooling sensor. It delivers the highest sensitivity of 6.9â nm/% at a concentration of 5% and the limit of detection (LOD) of pSi-sensor is 0.014% in case of ethanol in water when using an optical system with a resolution of 0.1â nm. Especially, the VOC method is capable of detecting low volume concentration of methanol in two tested ethanol solutions of 30% (v/v) and 45% (v/v) with the LOD of pSi-sensor up to 0.01% and 0.04%, respectively. This result will help pave a way to control the quality of contaminated liquor beverages.
Subject(s)
Volatile Organic Compounds , Humans , Limit of Detection , Porosity , Silicon , SolventsABSTRACT
The necessity of environmental protection has stimulated the development of many kinds of methods allowing the determination of different pollutants in the natural environment, including methods for determining nitrate in source water. In this paper, the characteristics of an etched fiber Bragg grating (e-FBG) sensing probe-which integrated in fiber laser structure-are studied by numerical simulation and experiment. The proposed sensor is demonstrated for determination of the low nitrate concentration in a water environment. Experimental results show that this sensor could determine nitrate in water samples at a low concentration range of 0-80 ppm with good repeatability, rapid response, and average sensitivity of 3.5 × 10-3 nm/ppm with the detection limit of 3 ppm. The e-FBG sensing probe integrated in fiber laser demonstrates many advantages, such as a high resolution for wavelength shift identification, high optical signal-to-noise ratio (OSNR of 40 dB), narrow bandwidth of 0.02 nm that enhanced accuracy and precision of wavelength peak measurement, and capability for optical remote sensing. The obtained results suggested that the proposed e-FBG sensor has a large potential for the determination of low nitrate concentrations in water in outdoor field work.
ABSTRACT
Low pump threshold upconversion narrowband emission at 537 nm in a simple system of erbium-doped silica microsphere at the tip of a fiber is reported. The emission comes out radially (not from whispering gallery modes) and is strongly enhanced by a thin metal coating, in particular with platinum. This enhancement seems to be related to the coupling with surface plasmons. The emission wavelength does not correspond to any energy level differences of erbium in silica, and is the same that was reported earlier in a coated fiber.
