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1. Facile Functionalization of Graphene to Tune Response of Printed Electrochemical Sensors to Neurotransmitters

   https://doi.org/10.1149/MA2023-01532651mtgabs  

   Kammarchedu, Vinay ; Butler, Derrick ; Khamsi, Pouya Soltan ; Ebrahimi, Aida ( August 2023 , ECS Meeting Abstracts)

   Neurotransmitters are small molecules involved in neuronal signaling and can also serve as stress biomarkers.¹Their abnormal levels have been also proposed to be indicative of several neurological diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington disease, among others. Hence, measuring their levels is highly important for early diagnosis, therapy, and disease prognosis. In this work, we investigate facile functionalization methods to tune and enhance sensitivity of printed graphene sensors to neurotransmitters. Sensors based on direct laser scribing and screen-printed graphene ink are studied. These printing methods offer ease of prototyping and scalable fabrication at low cost.

   The effect of functionalization of laser induced graphene (LIG) by electrodeposition and solution-based deposition of TMDs (molybdenum disulfide²and tungsten disulfide) and metal nanoparticles is studied. For different processing methods, electrochemical characteristics (such as electrochemically active surface area: ECSA and heterogenous electron transfer rate: k⁰) are extracted and correlated to surface chemistry and defect density obtained respectively using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. These functionalization methods are observed to directly impact the sensitivity and limit of detection (LOD) of the graphene sensors for the studied neurotransmitters. For example, as compared to bare LIG, it is observed that electrodeposition of MoS₂on LIG improves ECSA by 3 times and k⁰by 1.5 times.³Electrodeposition of MoS₂also significantly reduces LOD of serotonin and dopamine in saliva, enabling detection of their physiologically relevant concentrations (in pM-nM range). In addition, chemical treatment of LIG sensors is carried out in the form of acetic acid treatment. Acetic acid treatment has been shown previously to improve C-C bonds improving the conductivity of LIG sensors.⁴In our work, in particular, acetic acid treatment leads to larger improvement of LOD of norepinephrine compared to MoS₂electrodeposition.

   In addition, we investigate the effect of plasma treatment to tune the sensor response by modifying the defect density and chemistry. For example, we find that oxygen plasma treatment of screen-printed graphene ink greatly improves LOD of norepinephrine up to three orders of magnitude, which may be attributed to the increased defects and oxygen functional groups on the surface as evident by XPS measurements. Defects are known to play a key role in enhancing the sensitivity of 2D materials to surface interactions, and have been explored in tuning/enhancing the sensor sensitivity.⁵Building on our previous work,³we apply a custom machine learning-based data processing method to further improve that sensitivity and LOD, and also to automatically benchmark different molecule-material pairs.

   Future work includes expanding the plasma chemistry and conditions, studying the effect of precursor mixture in laser-induced solution-based functionalization, and understanding the interplay between molecule-material system. Work is also underway to improve the machine learning model by using nonlinear learning models such as neural networks to improve the sensor sensitivity, selectivity, and robustness.

   References

   A. J. Steckl, P. Ray, (2018), doi:10.1021/acssensors.8b00726.

   Y. Lei, D. Butler, M. C. Lucking, F. Zhang, T. Xia, K. Fujisawa, T. Granzier-Nakajima, R. Cruz-Silva, M. Endo, H. Terrones, M. Terrones, A. Ebrahimi,Sci. Adv.6, 4250–4257 (2020).

   V. Kammarchedu, D. Butler, A. Ebrahimi,Anal. Chim. Acta.1232, 340447 (2022).

   H. Yoon, J. Nah, H. Kim, S. Ko, M. Sharifuzzaman, S. C. Barman, X. Xuan, J. Kim, J. Y. Park,Sensors Actuators B Chem.311, 127866 (2020).

   T. Wu, A. Alharbi, R. Kiani, D. Shahrjerdi,Adv. Mater.31, 1–12 (2019).

    

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2. A Highly Sensitive and Long‐Term Stable Wearable Patch for Continuous Analysis of Biomarkers in Sweat

   https://doi.org/10.1002/adfm.202306117  

   Lorestani, Farnaz ; Zhang, Xianzhe ; Abdullah, Abu Musa ; Xin, Xin ; Liu, Yushen ; Rahman, Md Mashfiqur ; Biswas, Md Abu Sayeed ; Li, Bowen ; Dutta, Ankan ; Niu, Zhenyuan ; et al ( September 2023 , Advanced Functional Materials)

   Although increasing efforts have been devoted to the development of non‐invasive wearable electrochemical sweat sensors for monitoring physiological and metabolic information, most of them still suffer from poor stability and specificity over time and fluctuating temperatures. This study reports the design and fabrication of a long‐term stable and highly sensitive flexible electrochemical sensor based on nanocomposite‐modified porous graphene by facile laser treatment for detecting biomarkers such as glucose in sweat. The laser‐reduced and patterned stable conductive nanocomposite on the porous graphene electrode provides the resulting glucose sensor with an excellent sensitivity of 1317.69 µA mm⁻¹cm⁻²and an ultra‐low limit of detection of 0.079 µm. The sensor can also detect pH and exhibit extraordinary stability to maintain more than 91% sensitivity over 21 days in ambient conditions. Taken together with a temperature sensor based on the same material system, the dual glucose and pH sensor integrated with a flexible microfluidic sweat sampling network further results in accurate continuous on‐body glucose detection calibrated by the simultaneously measured pH and temperature. The low‐cost, highly sensitive, and long‐term stable platform could facilitate the early identification and continuous monitoring of different biomarkers for non‐invasive disease diagnosis and treatment evaluation.

    

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3. Ion‐Selective Sensors Based on Laser‐Induced Graphene for Evaluating Human Hydration Levels Using Urine Samples

   https://doi.org/10.1002/admt.201901037  

   Kucherenko, Ivan S. ; Sanborn, Delaney ; Chen, Bolin ; Garland, Nate ; Serhan, Michael ; Forzani, Erica ; Gomes, Carmen ; Claussen, Jonathan C. ( May 2020 , Advanced Materials Technologies)

   Complex graphene electrode fabrication protocols including conventional chemical vapor deposition and graphene transfer techniques as well as more recent solution‐phase printing and postprint annealing methods have hindered the wide‐scale implementation of electrochemical devices including solid‐state ion‐selective electrodes (ISEs). Herein, a facile graphene ISE fabrication technique that utilizes laser induced graphene (LIG), formed by converting polyimide into graphene by a CO₂laser and functionalization with ammonium ion (NH₄⁺) and potassium ion (K⁺) ion‐selective membranes, is demonstrated. The electrochemical LIG ISEs exhibit a wide sensing range (0.1 × 10⁻³–150 × 10⁻³mfor NH₄⁺and 0.3 × 10⁻³–150 × 10⁻³mfor K⁺) with high stability (minimal drop in signal after 3 months of storage) across a wide pH range (3.5–9.0). The LIG ISEs are also able to monitor the concentrations of NH₄⁺and K⁺in urine samples (29–51% and 17–61% increase for the younger and older patient; respectively, after dehydration induction), which correlate well with conventional hydration status measurements. Hence, these results demonstrate a facile method to perform in‐field ion sensing and are the first steps in creating a protocol for quantifying hydration levels through urine testing in human subjects.

    

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4. High Sensitivity Graphene Field Effect Transistor‐Based Detection of DNA Amplification

   https://doi.org/10.1002/adfm.202001031  

   Ganguli, Anurup ; Faramarzi, Vahid ; Mostafa, Ariana ; Hwang, Michael T. ; You, Seungyong ; Bashir, Rashid ( May 2020 , Advanced Functional Materials)

   Enzymatic DNA amplification‐based approaches involving intercalating DNA‐binding fluorescent dyes and expensive optical detectors are the gold standard for nucleic acid detection. As components of a simplified and miniaturized system, conventional silicon‐based ion sensitive field effect transistors (ISFETs) that measure a decrease in pH due to the generation of pyrophosphates during DNA amplification have been previously reported. In this article, Bst polymerase in a loop‐mediated isothermal amplification (LAMP) reaction combined with target‐specific primers and crumpled graphene field effect transistors (gFETs) to electrically detect amplification by sensing the reduction in primers is used. Graphene is known to adsorb single‐stranded DNA due to noncovalent π–π bonds, but not double‐stranded DNA. This approach does not require any surface functionalization and allows the detection of primer concentrations at the endpoint of reactions. As recently demonstrated, the crumpled gFET over the conventional flat gFET sensors due to their superior sensitivity is chosen. The endpoint of amplification reaction with starting concentrations down to 8 × 10⁻²¹min 90 min including the time of amplification and detection is detected. With its high sensitivity and small footprint, this platform will help bring complex lab‐based diagnostic and genotyping amplification assays to the point‐of‐care.

    

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5. Metallic 1T Phase Tungsten Disulfide Microflowers for Trace Level Detection of Hg 2+ Ions

   https://doi.org/10.1002/adsu.202000068  

   Rahman, Md Tawabur ; Maruf, Abdullah Al ; Faisal, Sakib ; Pathak, Rajesh ; Reza, Khan Mamun ; Gurung, Ashim ; Hummel, Matthew ; Gu, Zhengrong ; Laskar, Md Ashiqur Rahman ; Rahman, Sheikh Ifatur ; et al ( June 2020 , Advanced Sustainable Systems)

   Electrochemical sensors for mercury ion detection would ideally demonstrate wide linear detection ranges (LDRs), ultratrace sensitivity, and high selectivity. This work presents an electrochemical sensor based on metallic 1T phase tungsten disulfide (WS₂) microflowers for the detection of trace levels of Hg²⁺ions with wide LDRs, ultratrace sensitivity, and high selectivity. Under optimized conditions, the sensor shows excellent sensitivities for Hg²⁺with LDRs of 1 nm–1 µmand 0.1–1 mm. In addition to this, the limit of detection of the sensor toward Hg²⁺is 0.0798 nmor 79.8 pm, which is well below the guideline value recommended by the World Health Organization. The sensor exhibits excellent selectivity for Hg²⁺against other heavy metal ions including Cu²⁺, Fe³⁺, Ni²⁺, Pb²⁺, Cr³⁺, K⁺, Na⁺, Ag⁺, Sn²⁺, and Cd²⁺. The thus‐obtained excellent sensitivity and selectivity with wide LDRs can be attributed to the high conductivity, large surface area microflower structured 1T‐WS₂, and the complexation of Hg²⁺ions with S²⁻. In addition to good repeatability, reproducibility, and stability, this sensor shows the practical feasibility of Hg²⁺detection in tap water suggesting a promising device for real applications.

    

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