• 2D Hexagonal Boron Nitride (2D-hBN) Explored for the Electrochemical Sensing of Dopamine

      Khan, Aamar F.; Brownson, Dale A. C.; Randviir, Edward P.; Smith, Graham C.; Banks, Craig E.; Manchester Metropolitan University (Khan, Brownson, Randviir, Banks); University of Chester (Smith) (American Chemical Society, 2016-09-23)
      Crystalline 2D hexagonal boron nitride (2D-hBN) nanosheets are explored as a potential electrocatalyst toward the electroanalytical sensing of dopamine (DA). The 2D-hBN nanosheets are electrically wired via a drop-casting modi fication process onto a range of commercially available carbon supporting electrodes, including glassy carbon (GC), boron-doped diamond (BDD), and screen-printed graphitic electrodes (SPEs). 2D-hBN has not previously been explored toward the electrochemical detection/electrochemical sensing of DA. We critically evaluate the potential electrocatalytic performance of 2D-hBN modified electrodes, the effect of supporting carbon electrode platforms, and the effect of “mass coverage” (which is commonly neglected in the 2D material literature) toward the detection of DA. The response of 2D-hBN modified electrodes is found to be largely dependent upon the interaction between 2D-hBN and the underlying supporting electrode material. For example, in the case of SPEs, modification with 2D-hBN (324 ng) improves the electrochemical response, decreasing the electrochemical oxidation potential of DA by ∼ 90 mV compared to an unmodified SPE. Conversely, modification of a GC electrode with 2D-hBN (324 ng) resulted in an increased oxidation potential of DA by ∼ 80 mV when compared to the unmodified electrode. We explore the underlying mechanisms of the aforementioned examples and infer that electrode surface interactions and roughness factors are critical considerations. 2D-hBN is utilized toward the sensing of DA in the presence of the common interferents ascorbic acid (AA) and uric acid (UA). 2D-hBN is found to be an effective electrocatalyst in the simultaneous detection of DA and UA at both pH 5.0 and 7.4. The peak separations/resolution between DA and UA increases by ∼ 70 and 50 mV (at pH 5.0 and 7.4, respectively, when utilizing 108 ng of 2D-hBN) compared to unmodified SPEs, with a particularly favorable response evident in pH 5.0, giving rise to a significant increase in the peak current of DA. The limit of detection (3σ) is found to correspond to 0.65 μM for DA in the presence of UA. However, it is not possible to deconvolute the simultaneous detection of DA and AA. The observed electrocatalytic effect at 2D-hBN has not previously been reported in the literature when supported upon carbon or any other electrode. We provide valuable insights into the modifier −substrate interactions of this material, essential for those designing, fabricating, and consequently performing electrochemical experiments utilizing 2D-hBN and related 2D materials.
    • Graphite Screen-Printed Electrodes Applied for the Accurate and Reagentless Sensing of pH

      Galdino, Flávia E.; Smith, Jamie P.; Kwamou, Sophie I.; Kampouris, Dimitrios K.; Iniesta, Jesus; Smith, Graham C.; Bonacin, Juliano A.; Banks, Craig E.; University of Campinas, Brazil (Galdino, Bonacin), Manchester Metropolitain University (JP Smith, Kampouris, Banks), Universite Paris Est Creteil, France (Kwamou), University of Alicante, Spain (Inestia), University of Chester (GC Smith) (American Chemical Society, 2015-11-12)
      A reagentless pH sensor based upon disposable and economical graphite screen-printed electrodes (GSPEs) is demonstrated for the first time. The voltammetric pH sensor utilises GSPEs which are chemically pre-treated to form surface immobilised oxygenated species that when their redox behaviour is monitored, give a Nernstian response over a large pH range (1-13). An excellent experimental correlation is observed between the voltammetric potential and pH over the entire pH range of 1-13, such a response is not usually expected but rather deviation from linearity is encountered at alkaline pH values; absence of this has previously been attributed to a change in pKa value of surface immobilised groups. This non-deviation, which is observed here in the case of our facile produced reagentless pH sensor and also reported in the literature for pH sensitive compounds immobilized upon carbon electrodes/surfaces,where a linear response is observed over the entire pH range, is explained alternatively for the first time. The performance of the GSPE pH sensor is directly compared with a glass pH probe and applied to the measurement of pH in real samples where an excellent correlation between the two protocols is observed validating the proposed GSPE pH sensor.