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1. Laser-induced atmospheric Cu _x O formation on copper surface with enhanced electrochemical performance for non-enzymatic glucose sensing

   https://doi.org/10.1039/d1tc01289d  

   Sedaghat, Sotoudeh ; Nejati, Sina ; Bermejo, Luis Helena ; He, Zihao ; Alcaraz, Alejandro M. ; Roth, Alexander ; Li, Zheng ; Pol, Vilas G. ; Wang, Haiyan ; Rahimi, Rahim ( November 2021 , Journal of Materials Chemistry C)

   Copper oxide nanostructures are widely used for various applications due to their unique optical and electrical properties. In this work, we demonstrate an atmospheric laser-induced oxidation technique for the fabrication of highly electrochemically active copper oxide hierarchical micro/nano structures on copper surfaces to achieve highly sensitive non-enzymatic glucose sensing performance. The effect of laser processing power on the composition, crystallinity, microstructure, wettability, and color of the laser-induced oxide on copper (LIO-Cu) surface was systematically studied using scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GI-XRD), Raman spectroscopy, energy dispersive X-ray spectroscopy (EDX), EDX-mapping, water contact angle measurements, and optical microscopy. Results of these investigations showed a remarkable increase in copper oxide composition by increasing the laser processing power. The pore size distribution and surface area of the pristine and LIO-Cu sample estimated by N 2 adsorption–desorption data showed a developed mesoporous LIO-Cu structure. The size of the generated nano-oxides, crystallinity, and electroactivity of the LIO-Cu were observed to be adjustable by the laser processing power. The electrocatalytic activity of LIO-Cu surfaces was studied by means of cyclic voltammetry (CV) within a potential window of −0.8 to +0.8 V and chronoamperometry in an applied optimized potential of +0.6 V, in 0.1more »M NaOH solution and phosphate buffer solution (PBS), respectively. LIO-Cu surfaces with optimized laser processing powers exhibited a sensitivity of 6950 μA mM −1 cm −2 within a wide linear range from 0.01 to 5 mM, with exceptional specificity and response time (<3 seconds). The sensors also showed excellent response stability over a course of 50 days that was originated from the binder-free robust electroactive film fabricated directly onto the copper surface. The demonstrated one-step LIO processing onto commercial metal films, can potentially be applied for tuneable and scalable roll-to-roll fabrication of a wide range of high surface area metal oxide micro/nano structures for non-enzymatic biosensing and electrochemical applications.« less
2. Gold and silver oxide conducting nanocomposite cathode for glucose biofuel cell

   https://doi.org/10.1109/SENSORS47087.2021.9639600  

   Banerjee, Saikat ; Nguyen, Mathew ; Slaughter, Gymama ( October 2021 , 2021 IEEE Sensors)

   A glucose biofuel cell on a flexible bacterial nanocellulose film was prepared. The bioelectrodes were printed using gold ink as the conductive material. The anode was modified with colloidal platinum for the oxidation of glucose. The cathode was modified with a nanocomposite comprising gold nanoparticles (AuNPs) and silver oxide (Ag2O) nanoparticles. The cathode was characterized via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and UV spectroscopy techniques. The assembled biofuel cell generated a maximum open circuit voltage (V oc ) of 0.485 V, short circuit current (I sc ) of 0.352 mA/cm 2 , and a maximum peak power density (P max ) of 0.032 mW/cm 2 when operating in 30 mM concentration. This system showed a stable and linear performance with a linear range of 1 mM to 30 mM glucose. The gold printed electrode process is applicable to the development of wearable and implantable abiotic biofuel cell.
3. Laser induced graphene-based glucose biofuel cell

   https://doi.org/10.1109/SENSORS47087.2021.9639554  

   Hossain, Md Faruk ; Slaughter, Gymama ( October 2021 , 2021 IEEE Sensors)

   A glucose biofuel cell is presented using laser induced 3D graphene (LIG) substrate integrated with catalytic active nanomaterials for harnessing the biochemical energy of glucose. The LIG anode comprised glucose dehydrogenase immobilized on reduced graphene oxide and multiwalled carbon nanotubes (RGO/MWCNTs) nanocomposite for glucose oxidation. The LIG cathode is modified with RGO/MWCNTs and silver oxide (Ag 2 O) nanocomposites for the reduction of oxygen. The assembled biofuel cell exhibited a linear peak power response up to 18 mM glucose with sensitivity of 0.63 μW mM -1 cm −2 and exhibited good linearity (r 2 = 0.99). The glucose biofuel cell showed an open-circuit voltage of 0.365 V, a maximum power density of 11.3 μW cm −2 at a cell voltage of 0.25 V, and a short-circuit current density of 45.18 μA cm −2 when operating in 18 mM glucose. Cyclic voltammetry revealed the bioanode exhibited similar linearity for the detection of glucose. These results demonstrate that LIG based bioelectrodes offer great promise for diverse applications in the development of hybrid biofuel cell and biosensor technology.
4. A Study of the Effect of Electrochemical Roughening of Platinum on the Sensitivity and Selectivity of Glutamate Biosensors

   https://doi.org/10.1149/1945-7111/ac5ad5  

   Tan, Chao ; Yin, Haocheng ; Brooks, Victoria ; Arumugam, Prabhu U. ; Siddiqui, Shabnam ( March 2022 , Journal of The Electrochemical Society)

   A systematic study of electrochemically roughened (ECR) thin film platinum (Pt) microelectrodes for glutamate, GLU (a major excitatory neurotransmitter) detection is presented. Scanning electron microscopy, energy dispersive spectroscopy, surface profilometry, electrochemical impedance spectroscopy and amperometry techniques were applied to investigate the effect of high-frequency electrical pulses on Pt microelectrode roughness, electroactive area, charge transfer resistance, and sensitivity and selectivity to hydrogen peroxide, a by-product of enzymatic biosensors and GLU. An increase in the mean surface roughness from 9.0 ± 0.5 to 116.3 ± 7.4 nm (n = 3) was observed which resulted in a 55 ± 2% (n = 3) increase in the electroactive area. An ECR microelectrode treated at +1.4 V and coated with a selective coating produced a GLU selectivity value of 342 ± 34 (n = 3) vs ascorbic acid and the highest GLU sensitivity of 642 ± 45 nAμM⁻¹cm⁻²(n = 3) when compared to other surface-treated Pt microelectrodes reported in the literature. An impedance model was created to elucidate the microstructural and electrochemical property changes to the ECR microelectrodes. The ECR surface comprises of uniformly distributed homogenous pores with very low impedance, which is ∼6-times lower when compared to a methanol cleaned electrode. The model couldmore »lay a foundation for the rational designing of biosensors for enhanced neurotransmitter detection.

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5. A Fully-Flexible Solution-Processed Autonomous Glucose Indicator

   https://doi.org/10.1038/s41598-019-43425-x  

   Yuen, Jonathan D. ; Baingane, Ankit ; Hasan, Qumrul ; Shriver-Lake, Lisa C. ; Walper, Scott A. ; Zabetakis, Daniel ; Breger, Joyce C. ; Stenger, David A. ; Slaughter, Gymama ( May 2019 , Scientific Reports)

   We present the first demonstration of a fully-flexible, self-powered glucose indicator system that synergizes two flexible electronic technologies: a flexible self-powering unit in the form of a biofuel cell, with a flexible electronic device - a circuit-board decal fabricated with biocompatible microbial nanocellulose. Our proof-of-concept device, comprising an enzymatic glucose fuel cell, glucose sensor and a LED indicator, does not require additional electronic equipment for detection or verification; and the entire structure collapses into a microns-thin, self-adhering, single-centimeter-square decal, weighing less than 40 mg. The flexible glucose indicator system continuously operates a light emitting diode (LED) through a capacitive charge/discharge cycle, which is directly correlated to the glucose concentration. Our indicator was shown to operate at high sensitivity within a linear glucose concentration range of 1 mM–45 mM glucose continuously, achieving a 1.8 VDC output from a flexible indicator system that deliver sufficient power to drive an LED circuit. Importantly, the results presented provide a basis upon which further development of indicator systems with biocompatible diffusing polymers to act as buffering diffusion barriers, thereby allowing them to be potentially useful for low-cost, direct-line-of-sight applications in medicine, husbandry, agriculture, and the food and beverage industries.