Publications

@article{Somekh2024-oz,

title = {Common framework for surface plasmon binding and voltage sensing  and microscopy with transmission line representation},

author = {Michael G Somekh and Karen Regules-Medel and Sidahmed A Abayzeed},

doi = {10.1364/JOSAA.534360},

year  = {2024},

date = {2024-11-01},

urldate = {2024-11-01},

journal = {J. Opt. Soc. Am. A Opt. Image Sci. Vis.},

volume = {41},

number = {11},

pages = {C90\textendashC98},

publisher = {Optica Publishing Group},

abstract = {Surface plasmon imaging and sensing is a well-established and 

 important technology for the detection of minute binding events 

 in, for instance, antibody/antigen reactions. More recently it 

 has been realized that surface plasmon effects can be used to 

 measure voltages as well as electrical impedance. At first sight 

 the physical mechanisms for binding and voltage sensing appear 

 very different; however, we develop a transmission line and 

 impedance representation of the sensing process which clearly 

 shows that binding and voltage sensing can be conveniently 

 represented in a common framework. Our transmission line model 

 shows graphically how the gold layer amplifies reflectivity 

 changes resulting in optimum sensitivity at around 48 nm gold 

 thickness. The other elegant feature of this representation is 

 that the model clearly shows the role of the change in amplitude 

 and phase in the sensing process; indeed it reveals their 

 relative contribution to the output of the sensor. The graphical 

 representation is also very suggestive of a model to quantify 

 the performance of different detection strategies. This model 

 provides a framework to describe these strategies without 

 reference to any specific noise mechanisms. The results of the 

 model definitively support previous assertions that phase 

 imaging gives better sensitivity compared to intensity 

 measurement. Moreover, we show that measurement of the complex 

 amplitude containing both amplitude and phase of the detected 

 signal performs even better than phase only detection. This 

 opens the way for further enhancements of detection sensitivity.},

keywords = {localised surface plasmon resonance, voltage sensing},

pubstate = {published},

tppubtype = {article}

}

@article{He2021-uj,

title = {Volatile organic compound vapour measurements using a localised 

 surface plasmon resonance optical fibre sensor decorated with a 

 metal-organic framework},

author = {Chenyang He and Liangliang Liu and Sergiy Korposh and Ricardo Correia and Stephen P Morgan},

year  = {2021},

date = {2021-02-01},

journal = {Sensors (Basel)},

volume = {21},

number = {4},

pages = {1420},

publisher = {MDPI AG},

abstract = {A tip-based fibreoptic localised surface plasmon resonance 

 (LSPR) sensor is reported for the sensing of volatile organic 

 compounds (VOCs). The sensor is developed by coating the tip of 

 a multi-mode optical fibre with gold nanoparticles (size: 40 nm) 

 via a chemisorption process and further functionalisation with 

 the HKUST-1 metal-organic framework (MOF) via a layer-by-layer 

 process. Sensors coated with different cycles of MOFs (40, 80 

 and 120) corresponding to different crystallisation processes 

 are reported. There is no measurable response to all tested 

 volatile organic compounds (acetone, ethanol and methanol) in 

 the sensor with 40 coating cycles. However, sensors with 80 and 

 120 coating cycles show a significant redshift of resonance 

 wavelength (up to ~9 nm) to all tested volatile organic 

 compounds as a result of an increase in the local refractive 

 index induced by VOC capture into the HKUST-1 thin film. Sensors 

 gradually saturate as VOC concentration increases (up to 3.41%, 

 4.30% and 6.18% in acetone, ethanol and methanol measurement, 

 respectively) and show a fully reversible response when the 

 concentration decreases. The sensor with the thickest film 

 exhibits slightly higher sensitivity than the sensor with a 

 thinner film. The sensitivity of the 120-cycle-coated MOF sensor is 13.7 nm/% (R2 = 0.951) with a limit of detection (LoD) of 0.005% in the measurement of acetone, 15.5 nm/% (R2 = 0.996) 

 with an LoD of 0.003% in the measurement of ethanol and 6.7 nm/% (R2 = 0.998) with an LoD of 0.011% in the measurement of 

 methanol. The response and recovery times were calculated as 

 9.35 and 3.85 min for acetone; 5.35 and 2.12 min for ethanol; 

 and 2.39 and 1.44 min for methanol. The humidity and temperature 

 crosstalk of 120-cycle-coated MOF was measured as 0.5 $±$ 0.2 

 nm and 0.5 $±$ 0.1 nm in the humidity range of 50-75% 

 relative humidity (RH) and temperature range of 20-25 °C, 

 respectively.},

keywords = {localised surface plasmon resonance, metal-organic framework, optical fibre sensor, volatile organic compounds},

pubstate = {published},

tppubtype = {article}

}