We would like to thank Dr. Jonathan Newland for the photograph in Figure 4B and for processing optical microscope images for the video, Miss Jennifer Webb for advice and visuals on contact angle measurements, Miss Sze-yin Tan for the solvent window data in Figure 2B, Dr Maxim Joseph for advice on Raman spectroscopy, and also members of the Warwick Electrochemistry and Interfaces Group who have helped to develop the protocols described herein. We would also like to thank Max Joseph, Lingcong Meng, Zoe Ayres and Roy Meyler for their part in filming the protocol.

NOTE: BDD electrodes are most commonly grown using chemical vapor deposition techniques, attached to a growth substrate. They leave the growth chamber H-terminated (hydrophobic). If grown thick enough the BDD can be removed from the substrate and is termed freestanding. The freestanding BDD growth surface is often polished to significantly reduce surface roughness. Cleaning the BDD in acid results in an oxygen (O)-terminated surface.
1. Acid Cleaning BDD
<ol>
	<li>Place a beaker of concentrated sulfuric acid (H2SO4; ~ 2 ml or deep enough to cover the diamond) on a hot plate at RT and insert the BDD.</li>
	<li>Add potassium nitrate (KNO3) until it no longer dissolves (~ 0.5 g in 2 ml), then cover with a watch glass and heat to ~ 300 &#176;C, the solution will turn brown as it heats and the potassium nitrate will dissolve. 
	CAUTION! Care should be taken when handling hot acid; rubber gloves, safety glasses and lab coat should be worn and this process should be conducted in a fume hood.</li>
	<li>Leave to heat for at least 30 min or until there is no longer any brown color to the solution, then turn off the hot plate and leave the solution to cool to RT.</li>
	<li>Carefully dispose of the acid by diluting in RT water and rinse the BDD with distilled water.</li>
	<li>Measure the surface contact angle, see section 1.2. Hydrophobic (H-terminated)20,21 electrodes have reported contact angles in the range 60-90&#176;3, which significantly reduces as the surface is rendered hydrophilic through O-termination.</li>
	<li>(optional alternative method) For very thin film electrodes (attached to the growth substrate and to avoid film delamination using the above treatment), wash once with 2-propanol and twice with deionized water in an ultrasonic bath. Then, adopt one of the following three cleaning procedures (1) anodically polarize the diamond for 30 min at 10 mA cm-2 in 1 M perchloric acid at 40 &#176;C22; or (2) anodically polarize the diamond for 20 min at 10 mA cm-2 in 1 M nitric acid, then subsequently cathodically polarize at 10 mA cm-2 for a further 20 min in the same solution23 or; (3) cycle the diamond between 2 V in 0.1 M H2SO4 until a stable electrochemical signal is achieved7. Follow this with step 1.4.</li>
</ol>
2. Contact Angle Measurement
<ol>
	<li>Place the diamond on the sample stage of a contact angle analyzer, ensuring it is flat. Place a 1 ml syringe in the positioner above the sample stage, secure a needle on the end. Fill the syringe with deionized water.</li>
	<li>Use the z-controller to lower the syringe to the sample, use the x- and y- controllers and the camera/illuminator to align the syringe above the center of the diamond.</li>
	<li>Using the analyzer software dispense repeat 1 &#181;l volumes of water out of the syringe until a droplet forms at the tip of the needle, visible on the camera image (never more than 10 &#181;l). Lower the needle to deposit the droplet on to the surface and adjust the illumination for maximum contrast.</li>
	<li>Collect an image and apply drop shape analysis software, using the conic section method. Click &#34;find baseline&#34; in the software, and then click &#34;computation&#34; followed by &#34;tangent&#34;. 
	NOTE: this procedure detects the baseline and fits a conic equation to the (elliptical) drop shape; a contact angle, &#952;, is drawn between the baseline and the tangent at the three-phase contact point.</li>
</ol>
3. BDD Material Characterization
<ol>
	<li>Raman Analysis for sp2/sp3 content
	<ol>
		<li>Carry out Raman (see reference14 for a guide to Practical Raman Spectroscopy) in several different areas of the BDD electrode,24 use of a 514.5 nm or 532 nm laser, which emphasizes sp2 content, is advocated.</li>
		<li>Turn on the micro-Raman spectrometer and allow ~30 min for the CCD Detector to cool down. Check the appropriate lens, diffraction grating and filters are in place for use with the laser of choice.</li>
		<li>Calibrate the system using a silicon (Si) calibration sample. Place the Si substrate in the instrument chamber and focus optically on the sample with the microscope. Shut the door to the chamber. Switch to laser view and check the laser spot is well defined and circular. Calibrate using the software, click &#34;tools&#34; followed by &#34;calibration&#34; then &#34;quick calibration&#34; then &#34;ok&#34;.</li>
		<li>Remove the Si substrate from the chamber and replace with the BDD electrode. Optically focus the microscope on the area of interest, switch to laser view and open the shutter to check that the laser is focused. Close the shutter.</li>
		<li>Take a Raman measurement using the software; click &#34;measurement&#34; then &#34;new&#34; then &#34;spectral acquisition.&#34; set the measurement wavenumber range to cover the features of interest, for BDD this is 200 - 1,800 cm-1; set the scan acquisition time (&#60;10 sec); set the laser power to 100% (for BDD) and; set the number of accumulations (repeat scans) to five (for BDD). If the resulting spectrum is very noisy more accumulations may be necessary. Press run and save the resulting spectrum for analysis. Take a picture of the area Raman was performed in using the live video. Save the image as a reference.</li>
		<li>Observe the peak ~ 1,332 cm-1 in the spectrum which indicates sp3 diamond (Figure 1); the broader the peak the more defects present3,25.</li>
		<li>Observe any NDC &#8212; indicated by a broad G peak centered at 1,575 cm-1 26, in the spectra (Figure 1A and 1B), originating from the stretching of paired sp2 sites; the greater the peak intensity the more NDC present. 
		NOTE: the &#960; bonds formed by sp2 C are more polarizable than sp3 &#963; bonds and are resonantly enhanced by visible lasers, leading to broader, more dominant, G peaks25. Note that the exact method used to perform analyses may vary between different instruments and software.</li>
	</ol>
	</li>
</ol>
4. Electrochemical Characterization
<ol>
	<li>Preparing ohmic contacts
	<ol>
		<li>Freestanding BDD
		<ol>
			<li>Using standard techniques sputter (or evaporate)the backside of the BDD with titanium (Ti)/gold (Au) 10 nm/300 nm, using a sputterer/evaporator at pressures below 1 &#215; 10-5 mBar. If a three target source is available, more ideally is Ti 10 nm / platinum (Pt) 10 nm / Au 300 nm to avoid diffusion of Ti into the Au.</li>
			<li>Anneal for 5 hr at 400 &#176;C (atmospheric pressure) enabling the Ti to form titanium carbide, crucial for formation of an ohmic contact27. 
			NOTE: if the back surface of the BDD is highly polished (~ nm roughness) then it is preferably to roughen the surface prior to sputter deposition to ensure a more robust coating. This can be achieved by, for example, low power laser micromachining the surface (removing &#60; 30 &#956;m material).</li>
		</ol>
		</li>
		<li>Thin film diamond grown on a conducting substrate
		<ol>
			<li>Sputter/evaporate as above, but to the top face, using a shadow mask gently place on the top surface to avoid top contacting the entire electrode. 
			OR</li>
			<li>Scratch the back of the conducting substrate using a diamond tipped pen. Then coat the scratched area with conducting Ag paste or a similar conductive paint by painting on a thin layer with a small paintbrush. Finally, electrically connect by attaching copper wires with conductive epoxy. 
			NOTE: there are a variety of ways to prepare the BDD after electrical contact as described in reference 4, e.g. if the BDD can be machined into smaller structures, seal in glass or epoxy, or if still attached to the wafer clamp/attach an electrochemical cell to the top surface.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Capacitance Measurements
	<ol>
		<li>Prepare a 20 ml of 0.1 M KNO3 solution by weighing 0.20 g in doubly distilled water (this water quality is recommended throughout, resistivity 18.2 M cm). Clean the electrode prior to use either by alumina polishing or by electrochemically cycling in dilute acid (see section 1 NOTE)16,23,28.</li>
		<li>Using a potentiostat run cyclic voltammograms (CVs) at 0.1 V sec-1 between -0.1 V and 0.1 V, starting at 0 V, with the BDD as the working electrode versus a common reference electrode, e.g. silver/silver chloride (Ag/AgCl) or a saturated calomel electrode (SCE), and a Pt counter electrode. Analyze the second CV. 
		NOTE: Figure 2A shows a typical capacitance curve recorded with a freestanding metallic doped BDD electrode.</li>
		<li>Measure the total current magnitude at 0 V from the recorded capacitance curve and divide by 2, this value is &#34;i&#34;. Determine the capacitance, C, using the value for i, with equation 1, normalize with respect to electrode area (accounting for surface roughness if appropriate) and quote in &#181;F cm-2. High quality, &#34;metal-like&#34; BDD has a capacitance &#60;&#60; 10 &#181;F cm-2. Use any data plotting software to present and analyze the data. 
		i = C(Vt-1)&#160;&#160; (eq. 1); 
		where i is current (A) and (V t-1) is the potential scan rate.</li>
	</ol>
	</li>
	<li>Solvent Window
	<ol>
		<li>Clean the electrode as in step 4.2.1. Using a potentiostat run a CV in 0.1 M KNO3 at 0.1 V sec-1 from 0 V to -2 V then between -2 V and +2 V and back to 0 V with the BDD as the working electrode vs. a common reference electrode and Pt counter electrode. Repeat. Analyze the second CV, an example CV is shown in Figure 2B.</li>
		<li>Convert current to current density (mA cm-2), taking surface roughness into account, and quote the solvent window as the potential window defined by current limits of &#177;0.4 mA cm-2 in both directions.7,29 Use any data plotting software to present and analyze the data.</li>
		<li>Observe the evidence of NDC (sp2 carbon) in the solvent window; the oxygen reduction reaction is favored on NDC that is clearly evident in the reductive window. Oxidation of sp2 containing groups also results in characteristic peaks just before water electrolysis in the anodic window (Figure 2B). 
		NOTE: high quality &#34;metallic&#34; BDD electrodes have solvent windows &#62;&#62; 3 V, do not support the oxygen reduction reaction (ORR) in 0.1 M KNO3 (or ORR is strongly kinetically retarded) and show negligible NDC oxidation signatures.</li>
	</ol>
	</li>
	<li>Redox Electrochemistry
	<ol>
		<li>Clean the electrode as in step 4.2.1.</li>
		<li>Using a potentiostat record CVs in 1 mM ruthenium hexaamine (Ru(NH3)63+) and 0.1 M KNO3 between +0.2 V and -0.8 V versus SCE, for scan rates in the range 0.05 V sec-1- 0.2 V sec-1. 
		NOTE: This couple shows fast electron transfer and is electroactive in a region which challenges p-type semiconducting BDD. sp2 containing BDD will also show ORR in this region, the signal for the latter is more evident as the concentration of Ru(NH3)63+ is decreased.</li>
		<li>Measure the voltage separation between the anodic and cathodic peak current (&#916;Ep) from the recorded CV, and the temperature as described20. For &#34;metal-like&#34; ohmically contacted oxygen-terminated BDD at 298 K, &#916;Ep &#60; 70 mV30,31. Larger &#916;Ep values are symptomatic of a poor ohmic contact or a lower boron content, as shown in Figure 2C for BDD electrodes of dopant densities in the range 9.2 &#215; 1016 to 3 &#215; 1020 B atoms cm-3.</li>
		<li>Measure the peak current of the forward scan, ip, and correlate with that expected from the Randles Sevcik equation 2 (quoted at 298 K)3,30, assuming the electrode is disk-shaped in geometry and large enough (diameter 1 mm) that linear diffusion dominates. Use any data plotting software to present and analyze the data. 
		ip = 2.69 &#215; 105 n3/2 AD1/2 cv1/2&#160;&#160; (eq 2) 
		where n is the number of electrons transferred, A is area (cm2), D is diffusion coefficient (cm2 sec-1), c is concentration (mol cm-3) and v is scan rate (V sec-1).</li>
	</ol>
	</li>
</ol>
5. pH Generation: Preparation of pH Sensitive Electrode and pH Generation
<ol>
	<li>Iridium Oxide (pH sensitive) Solution Preparation
	<ol>
		<li>Prepare a 20 ml 0.1 M KNO3 solution as in section 5.4.1. Add 5 drops of phenolphthalein indicator solution using a Pasteur pipette and stir (this is sufficient to see a response by eye, but for a more intense color, add more drops). Place the BDD working electrode and Pt counter electrode in solution.</li>
		<li>Adjust pH of the solution to 10.5 by addition of anhydrous potassium chloride salt, stirring continuously. Leave covered and stirring for 48 hr at RT to stabilize, at this stage the solution will gradually go from yellow-green to blue-purple. Store in a refrigerator at 3 &#176;C.</li>
	</ol>
	</li>
	<li>pH Sensitive Iridium Oxide Film Deposition
	<ol>
		<li>Using a potentiostat run a CV in the iridium oxide solution between 0 V and +1 V versus SCE to determine the potential at which the maximum current is recorded. This is the deposition potential, Edep as shown in Figure 3A, typically lying between ~+0.6 V &#8211; +0.85 V; it can vary depending on a number of factors such as temperature, electrode material etc.32,33</li>
		<li>Using chronoamperometry with a potentiostat, step the potential from 0 V (&#34;initial E&#34; and &#34;Low E&#34; in the software), where no electrolysis occurs to Edep (&#34;High E&#34; in the software), for a time period of 0.2 sec per step, repeat 100x.</li>
		<li>Run a CV between 0 V and +1 V in 0.1 M H2SO4 for the IrOx deposited electrode. The characteristic CV shape is shown in Figure 3B. A current density in the range ~ 0.6 mA cm-2 - 0.7 mA cm-2 for the first anodic peak (corresponding to an average film thickness of ~ 8 nm for 0.7 mA cm-2), indicates a stable pH sensitive film34,35.</li>
		<li>If the current density is less than 0.6 mA cm-2 repeat steps 5.2.2 - 5.2.4 until this value is reached. Leave the electrode in pH 7 buffer solution for 24 hr to hydrate as the response of the IrOx film is hydration-dependant33.</li>
	</ol>
	</li>
	<li>IrOx Film pH Characterization
	<ol>
		<li>Prepare a series of buffer solutions which cover the pH range of interest (pH 2 - pH 12), these can be made in house (e.g. Carmody36) or purchased commercially.</li>
		<li>Rinse the electrode with distilled water. Place the IrOx electrode and reference electrode in the buffer solution of lowest pH. Using a potentiostat record the open circuit potential (OCP) over 30 sec, with three repeats. Remove the electrode from the solution, rinse and place in the next buffer.</li>
		<li>Repeat step 5.3.2 for each buffer, then repeat the series at least twice. Plot pH vs. OCP, the calibration plot for the film response. An IrOx film exhibits a slope with a gradient between 59 - 80 mV per decade37. 
		NOTE: Figure 3C shows an example calibration plot for a successful IrOx pH sensor on BDD.</li>
	</ol>
	</li>
	<li>Using a pH generator and measurement system 
	NOTE: this assumes use of a dual electrode system where one electrode is coated with the IrOx film (e.g. disc) and the second (e.g. BDD ring) will generate H+ or OH- galvanostatically from water electrolysis.
	<ol>
		<li>Prepare a 20 ml 0.1 M KNO3 solution by adding deionized water to the salt. Connect the IrOx coated electrode as the working electrode in a two electrode system, with the second electrode a stable reference electrode e.g. SCE. Measure the OCP using a potentiostat, to establish the starting pH.</li>
		<li>Connect the generator electrode to a suitable two electrode galvanostatic system with a counter electrode, e.g. Pt foil, and repeat step 5.4.1, but after a defined period of time apply a current to the generator electrode. 
		NOTE: we find currents in the range 0 to &#177; 50 &#956;A are suitable with our BDD electrodes; larger currents result in appreciable gas evolution. The magnitude and direction of the current depends on the desired result; a positive current will result in a shift to more acidic pH and a negative current to more alkaline pH, the larger the current the greater the pH change.</li>
		<li>Using the potentiostat, record the change in OCP in response to the galvanostatic current, wait until the response stabilizes. Then place the IrOx electrode in pH 7 buffer for 10 min to re-equilibrate the IrOx film.</li>
		<li>Repeat steps 5.4.2 to 5.4.3 with different applied currents, until all the data required has been collected. Plot the data using the calibration curve obtained in section 5.3 to convert OCP to pH, an example data set is shown in Figure 4A. Remove the IrOx film using alumina polishing or pulsing in 0.1 M H2SO4 from +2 V to -2 V for 0.2 sec, &#215;100. Apply to the measurement system of interest.</li>
	</ol>
	</li>
	<li>Visual assessment of local pH generation
	<ol>
		<li>Prepare a 20 ml 0.1 M KNO3 solution as in section 5.4.1. Add 5 drops of phenolphthalein indicator solution using a Pasteur pipette and stir (this is sufficient to see a response by eye, but for a more intense color, add more drops). Place the BDD working electrode and Pt counter electrode in solution.</li>
		<li>Apply a negative current to the working electrode using a galvanostat as in step 5.4.2 (e.g. ~ -0.6 mA cm-2) such that the solution changes color from colorless to pink. This now locally generates a solution which is at pH &#8805; 10.5.</li>
		<li>Repeat step 5.5.1 with 5 drops of methyl red solution instead of phenolphthalein and stir. Apply a sufficiently positive current (e.g. ~ 6.6 mA cm-2) such that the solution changes color from yellow to red. This now locally generates a solution which is at pH &#8804; 4.238.</li>
	</ol>
	</li>
</ol>

The authors declare that they have no competing financial interests.

Starting with an O-terminated surface is advocated because the H-terminated surface is electrochemically unstable, especially at high anodic potentials7,40,41. Changing surface termination can affect the electron transfer kinetics of inner sphere couples, such as water electrolysis (used herein to change the local solution pH). Furthermore, if the BDD contains significant NDC at grain boundaries it is also possible that upon application of the extreme anodic/cathodic potentials advocated in this article for pH...

Choice of electrode material is of great importance when conducting any electroanalytical study. In recent years, sp3 carbon (diamond) doped with sufficient boron to render the material &#34;metal-like&#34; has become a popular choice for a wide range of electroanalytical applications due to its excellent electrochemical (and thermal and mechanical) properties1,2,3. These include corrosion resistance under extreme solution, temperature and pressure conditions4 ultra-wide solvent windows, low background currents, and reduced fouling, in comparison to other commonly used electrode materials5-7,3. However, increasing non-diamond-carbon (NDC: sp2) content results in a decreasing solvent window, increasing background currents7,8, changes in both structural integrity and sensitivity towards different inner sphere redox species, e.g. oxygen9-12.
Note for some applications, NDC presence is seen as advantageous13. Furthermore, if the material does not contain sufficient boron it will behave as a p-type semi-conductor and show reduced sensitivity to redox species in the reductive potential window, where the material is most depleted of charge carriers7. Finally, the surface chemistry of boron doped diamond (BDD) can also play a role in the observed electrochemical response. This is especially true for inner sphere species which are sensitive to surface chemistry and lower doped diamond where a hydrogen (H-)-terminated surface may make a semi-conducting BDD electrode appear &#34;metal-like&#34;7.
To take advantage of the superior properties of BDD, it is often essential the material is sufficiently doped and contains as little NDC as possible. Dependent on the method adopted to grow the BDD, the properties can vary14,15. This paper first suggests a materials and an electrochemical characterization protocol guide for assessing BDD electrode suitability prior to use (i.e. sufficient boron, minimal NDC) and then describes one application based on locally changing pH electrochemically using the protocol-verified electrode. This process takes advantage of the surface resilience of NDC-free BDD towards corrosion or dissolution under application of extreme applied potentials (or currents) for long periods of time. In particular the use of a BDD electrode to generate stable proton (H+) or hydroxide (OH-) fluxes due to electrolysis (oxidation or reduction respectively) of water in close proximity to a second (sensor)16,17 is described herein.
In this way it is possible to control the pH environment of the sensor in a systematic way, e.g. for pH titration experiments, or to fix the pH at a value where the electrochemical process is most sensitive. The latter is especially useful for applications where the sensor is placed at the source, e.g. river, lake, sea and the pH of the system is not optimal for the electrochemical measurement of interest. Two recent examples include: (i) generation of a localized low pH, in a pH neutral solution, for the electrodeposition and stripping of mercury17; note BDD is a favored material for electrodeposition of metals due to the extended cathodic window9,18,19. (ii) Quantification of the electrochemically detectable form of hydrogen sulfide, present at high pH, by locally increasing the pH from neutral to strongly alkaline16.

<table border="0" cellpadding="0" cellspacing="0" width="373">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:117px;">Pt Wire</td>
			<td style="width:64px;"></td>
			<td style="width:75px;"></td>
			<td style="width:117px;">Counter Electrode</td>
		</tr>
		<tr height="100">
			<td height="100" style="height:100px;width:117px;">Saturated Calomel Electrode</td>
			<td style="width:64px;">IJ Cambria Scientific Ltd.</td>
			<td style="width:75px;">2056</td>
			<td style="width:117px;">Reference Electrode (alternatively use Ag|AgCl)</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">BDD Electrode</td>
			<td style="width:64px;"></td>
			<td style="width:75px;"></td>
			<td style="width:117px;">Working Electrode</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:117px;">Iridium Tetrachloride</td>
			<td style="width:64px;">VWR International Ltd</td>
			<td style="width:75px;">12184.01</td>
			<td style="width:117px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Hydrogen Peroxide</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">H1009</td>
			<td style="width:117px;">(30% w/w) Corrosive</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Oxalic Acid&#160;</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">241172</td>
			<td style="width:117px;">Harmful, Irritant</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:117px;">Anhydrous Potassium Chloride</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">451029</td>
			<td style="width:117px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:117px;">Sulphuric Acid</td>
			<td style="width:64px;">VWR International Ltd</td>
			<td style="width:75px;">102765G</td>
			<td style="width:117px;">(98%) Corrosive</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Potassium Nitrate</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">221295</td>
			<td style="width:117px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:117px;">Hexaamine Ruthenium Chloride</td>
			<td style="width:64px;">Strem Chemicals Inc.</td>
			<td style="width:75px;">44-0620</td>
			<td style="width:117px;">Irritant</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Perchloric Acid</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">311421</td>
			<td style="width:117px;">Oxidising, Corrosive</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">2-Propanol</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">24137</td>
			<td style="width:117px;">Flammable</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Nitric Acid</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">695033</td>
			<td style="width:117px;">Oxidising, Corrosive</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Sputter/ Evapourator</td>
			<td style="width:64px;"></td>
			<td style="width:75px;"></td>
			<td style="width:117px;">With Ti &#38; Au targets</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:117px;">Raman</td>
			<td style="width:64px;"></td>
			<td style="width:75px;"></td>
			<td style="width:117px;">514.5 nm laser</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:117px;">Annealing Oven</td>
			<td style="width:64px;"></td>
			<td style="width:75px;"></td>
			<td style="width:117px;">Capable of 400&#176;C</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Ag paste</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">735825</td>
			<td style="width:117px;">or other conductive paint</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:117px;">Potentiostat</td>
			<td style="width:64px;"></td>
			<td style="width:75px;"></td>
			<td style="width:117px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">pH Buffer solutions</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">38740-38752</td>
			<td style="width:117px;">Fixanal buffer concentrates</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:117px;">Phenolphthalein Indicator</td>
			<td style="width:64px;">VWR International Ltd</td>
			<td style="width:75px;">210893Q</td>
			<td style="width:117px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:117px;">Methyl Red Indicator</td>
			<td style="width:64px;">Sigma-Aldrich</td>
			<td style="width:75px;">32654</td>
			<td style="width:117px;"></td>
		</tr>
	</tbody>
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assessment of boron doped diamond electrode quality and application to in situ modification of local ph by water electrolysis

Boron doped diamond (BDD) electrodes have shown considerable promise as an electrode material where many of their reported properties such as extended solvent window, low background currents, corrosion resistance, etc., arise from the catalytically inert nature of the surface. However, if during the growth process, non-diamond-carbon (NDC) becomes incorporated into the electrode matrix, the electrochemical properties will change as the surface becomes more catalytically active. As such it is important that the electrochemist is aware of the quality and resulting key electrochemical properties of the BDD electrode prior to use. This paper describes a series of characterization steps, including Raman microscopy, capacitance, solvent window and redox electrochemistry, to ascertain whether the BDD electrode contains negligible NDC i.e. negligible sp2 carbon. One application is highlighted which takes advantage of the catalytically inert and corrosion resistant nature of an NDC-free surface i.e. stable and quantifiable local proton and hydroxide production due to water electrolysis at a BDD electrode. An approach to measuring the local pH change induced by water electrolysis using iridium oxide coated BDD electrodes is also described in detail.

Raman spectra and electrochemical characteristics were obtained for representative BDD macrodisc electrodes with different dopant densities, and both significant and negligible levels of NDC, Figures 1 and 2. Figures 1A and B show typical Raman data for NDC-containing thin film microcrystalline BDD and larger grain freestanding BDD, doped above the metallic threshold, respectively. The presence of NDC is identifiable by t...

Watch this Scientific Journal Video about Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis at JoVE.com

Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

A protocol is described for the characterization of the key electrochemical parameters of a boron doped diamond (BDD) electrode and subsequent application for in situ pH generation experiments.

Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

Boron doped diamond (BDD) electrodes have shown considerable promise as an electrode material where many of their reported properties such as extended ...

assessment-boron-doped-diamond-electrode-quality-application-to-situ

Research

JoVE Journal

Chemistry

14.7K Views.  University of Warwick. A protocol is described for the characterization of the key electrochemical parameters of a boron doped diamond (BDD) electrode and subsequent application for in situ pH generation experiments.

Video: Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

The development of fluorescent indicators represented a revolution for life sciences. Genetically encoded and synthetic fluorophores with sensing abilities allowed the visualization of biologically relevant species with high spatial and temporal resolution. Synthetic dyes are of particular interest thanks to their high tunability and the wide range of measureable analytes. However, these molecules suffer several limitations related to small molecule behavior (poor solubility, difficulties in targeting, often no ratiometric imaging allowed). In this work we introduce the development of dendrimer-based sensors and present a procedure for pH measurement in vitro, in living cells and in vivo. We choose dendrimers as ideal platform for our sensors for their many desirable properties (monodispersity, tunable properties, multivalency) that made them a widely used scaffold for several biomedical devices. The conjugation of fluorescent pH indicators to the dendrimer scaffold led to an enhancement of their sensing performances. In particular dendrimers exhibit reduced cell leakage, improved intracellular targeting and allow ratiometric measurements. These novel sensors were successfully employed to measure pH in living HeLa cells and in vivo in mouse brain.

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

Fluorescence sensors are powerful tools in life science. Here we describe a methodology to synthesize and use dendrimer-based fluorescent sensors to measure pH in living cells and in vivo. The dendritic scaffold enhances the properties of conjugated fluorescent dyes leading to improved sensing properties.

The development of  fluorescent indicators represented a revolution for life sciences. Genetically  encoded and synthetic fluorophores with sensing ...

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

This work demonstrates in situ characterization of protein biomolecules in the aqueous solution using the System for Analysis at the Liquid Vacuum Interface (SALVI) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The fibronectin protein film was immobilized on the silicon nitride (SiN) membrane that forms the SALVI detection area. During ToF-SIMS analysis, three modes of analysis were conducted including high spatial resolution mass spectrometry, two-dimensional (2D) imaging, and depth profiling. Mass spectra were acquired in both positive and negative modes. Deionized water was also analyzed as a reference sample. Our results show that the fibronectin film in water has more distinct and stronger water cluster peaks compared to water alone. Characteristic peaks of amino acid fragments are also observable in the hydrated protein ToF-SIMS spectra. These results illustrate that protein molecule adsorption on a surface can be studied dynamically using SALVI and ToF-SIMS in the liquid environment for the first time.

In Situ Characterization of Hydrated Proteins in Water by SALVI and ToF-SIMS

This work presents a protocol for liquid handling and sample introduction to a microchannel for in situ time-of-flight secondary ion mass spectrometry analysis of protein biomolecules in an aqueous solution.

This work demonstrates in situ characterization of protein biomolecules in the aqueous solution using the System for Analysis at the Liquid Vacuum ...

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS

Bacterial biofilms are surface-associated communities that are vastly studied to understand their self-produced extracellular polymeric substances (EPS) and their roles in environmental microbiology. This study outlines a method to cultivate biofilm attachment to the System for Analysis at the Liquid Vacuum Interface (SALVI) and achieve in situ chemical mapping of a living biofilm by time-of-flight secondary ion mass spectrometry (ToF-SIMS). This is done through the culturing of bacteria both outside and within the SALVI channel with our specialized setup, as well as through optical imaging techniques to detect the biofilm presence and thickness before ToF-SIMS analysis. Our results show the characteristic peaks of the Shewanella biofilm in its natural hydrated state, highlighting upon its localized water cluster environment, as well as EPS fragments, which are drastically different from the same biofilm's dehydrated state. These results demonstrate the breakthrough capability of SALVI that allows for in situ biofilm imaging with a vacuum-based chemical imaging instrument.

In Situ Characterization of Shewanella oneidensis MR1 Biofilms by SALVI and ToF-SIMS

This article presents a method for growing a biofilm for in situ time-of-flight secondary ion mass spectrometry for chemical mapping in its hydrated state, enabled by a microfluidic reactor, System for Analysis at the liquid Vacuum Interface. The Shewanella oneidensis MR-1 with green fluorescence protein was used as a model.

Bacterial biofilms are surface-associated communities that are vastly studied to understand their self-produced extracellular polymeric substances (EPS) ...

In Situ Characterization of Boehmite Particles in Water Using Liquid SEM

In situ imaging and elemental analysis of boehmite (AlOOH) particles in water is realized using the System for Analysis at the Liquid Vacuum Interface (SALVI) and Scanning Electron Microscopy (SEM). This paper describes the method and key steps in integrating the vacuum compatible SAVLI to SEM and obtaining secondary electron (SE) images of particles in liquid in high vacuum. Energy dispersive x-ray spectroscopy (EDX) is used to obtain elemental analysis of particles in liquid and control samples including deionized (DI) water only and an empty channel as well. Synthesized boehmite (AlOOH) particles suspended in liquid are used as a model in the liquid SEM illustration. The results demonstrate that the particles can be imaged in the SE mode with good resolution (i.e., 400 nm). The AlOOH EDX spectrum shows significant signal from the aluminum (Al) when compared with the DI water and the empty channel control. In situ liquid SEM is a powerful technique to study particles in liquid with many exciting applications. This procedure aims to provide technical know-how in order to conduct liquid SEM imaging and EDX analysis using SALVI and to reduce potential pitfalls when using this approach.

In Situ Characterization of Boehmite Particles in Water Using Liquid SEM

We present a procedure for real-time imaging and elemental composition analysis of boehmite particles in deionized water by in situ liquid Scanning Electron Microscopy.

In situ imaging and elemental analysis of boehmite (AlOOH) particles in water is realized using the System for Analysis at the Liquid Vacuum Interface ...

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables the silk proteins to be compact and ordered by shearing and elongation forces. Here, a biomimetic microfluidic channel was designed to mimic the specific geometry of the spinning duct of the silkworm. Regenerated silk fibroin (RSF) spinning doped with high concentration, was extruded through the microchannel to dry-spin fibers at ambient temperature and pressure. In the post-treated process, the as-spun fibers were drawn and stored in ethanol aqueous solution. Synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) technology was used to investigate the microstructure of single RSF fibers, which were fixed to a sample holder with the RSF fiber axis normal to the microbeam of the X-ray. The crystallinity, crystallite size, and crystalline orientation of the fiber were calculated from the WAXD data. The diffraction arcs near the equator of the two-dimensional WAXD pattern indicate that the post-treated RSF fiber has a high orientation degree.

A protocol for the microfluidic spinning and microstructure characterization of regenerated silk fibroin monofilament is presented.

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables ...

Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical properties, which allow for the absorption of near-infrared (NIR) light and can subsequently convert it into multiplexed emissions that span over a broad range of regions from the UV to the visible to the NIR. This article presents detailed experimental procedures for high-temperature co-precipitation synthesis of core-shell UCNs that incorporate different lanthanide ions into nanocrystals for efficiently converting deep-tissue penetrable NIR excitation (808 nm) into a strong blue emission at 480 nm. By controlling the surface modification with biocompatible polymer (polyacrylic acid, PAA), the as-prepared UCNs acquires great solubility in buffer solutions. The hydrophilic nanocrystals are further functionalized with specific ligands (dibenzyl cyclooctyne, DBCO) for localization on the cell membrane. Upon NIR light (808 nm) irradiation, the upconverted blue emission can effectively activate the light-gated channel protein on the cell membrane and specifically regulate the cation (e.g., Ca2+) influx in the cytoplasm. This protocol provides a feasible methodology for the synthesis of core-shell lanthanide-doped UCNs and subsequent biocompatible surface modification for further cellular applications.

A protocol is presented for the synthesis of core-shell lanthanide-doped upconversion nanocrystals (UCNs) and their cellular applications for channel protein regulation upon near-infrared (NIR) light illumination.

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical ...

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

In Situ Lithiated Reference Electrode: Four Electrode Design for In-operando Impedance Spectroscopy

Extending operating voltage of Li-ion batteries results in higher energy output from these devices. High voltages, however, may trigger or accelerate multiple processes responsible for long-term performance decay. Given the complexity of physical processes occurring inside the cell, it is often challenging to achieve a full understanding of the root causes of this performance degradation. This difficulty arises in part from the fact that any electrochemical measurement of a battery will return the combined contributions of all components in the cell. Incorporation of a reference electrode can solve part of the problem, as it allows the electrochemical reactions of the cathode and the anode to be individually probed. A variation in the voltage range experienced by the cathode, for example, can indicate alterations in the pool of cyclable lithium ions in the full-cell. The structural evolution of the many interphases existing in the battery can also be monitored, by measuring the contributions of each electrode to the overall cell impedance. Such wealth of information amplifies the reach of diagnostic analysis in Li-ion batteries and provides valuable input to the optimization of individual cell components. In this work, we introduce the design of a test cell able to accommodate multiple reference electrodes, and present reference electrodes that are appropriate for each specific type of measurement, detailing the assembly process in order to maximize the accuracy of the experimental results.

The incorporation of reference electrodes in a Li-ion battery provides valuable information to elucidate degradation mechanisms at high voltages. In this article, we present a cell design that accommodates multiple reference electrodes, along with the assembly steps to assure maximum accuracy of the data obtained in electrochemical measurements.

Extending operating voltage of Li-ion batteries results in higher energy output from these devices. High voltages, however, may trigger or accelerate ...

Negative Additive Manufacturing of Complex Shaped Boron Carbides

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for high wear, high hardness, and lightweight material applications such as armors. To overcome this challenge, negative additive manufacturing (AM) is employed to produce complex geometries of boron carbides at various length scales. Negative AM first involves gelcasting a suspension into a 3D-printed plastic mold. The mold is then dissolved away, leaving behind a green body as a negative copy. Resorcinol-formaldehyde (RF) is used as a novel gelling agent because unlike traditional hydrogels, there is little to no shrinkage, which allows for extremely complex molds to be used. Furthermore, this gelling agent can be pyrolyzed to leave behind ~50 wt% carbon, which is a highly effective sintering aid for B4C. Due to this highly homogenous distribution of in situ carbon within the B4C matrix, less than 2% porosity can be achieved after sintering. This protocol highlights in detail the methodology for creating near fully dense boron carbide parts with highly complex geometries.

A method called negative additive manufacturing is used to produce near fully dense complex shaped boron carbide parts of various length scales. This technique is possible via the formulation of a novel suspension involving resorcinol-formaldehyde as a unique gelling agent that leaves behind a homogenous carbon sintering aid after pyrolysis.

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for ...