Prussian Blue Nanotubes Research Articles

Electrochemical Paper-Based Platform for Micronutrient Sensing: Potassium Detection

Rapid quantification of ions is important for preventive care and diagnostics. This is particularly significant for emergency room and clinical settings, where a quick quantification of an electrolyte imbalance can guide required treatments. We are currently developing an alternative ion sensing platform. This platform will involve measurement of the shift in potential of the redox peak of an electroactive layer as a function of the presence of a targeted ion (Figure A - Scheme of cyclic voltammograms shifting due to the increasing concentration of potassium ions in tested solution). This is caused by the intercalation of the ion into the electrodeposited layer (Figure B - Concept of electroactive sensing layer immobilized on electrode). One ion of interest is potassium. The potassium ion is present in the human body at 3.5 – 5.0 mmol/L [1]. A patient that is below the healthy range can be diagnosed with hypokalemia. This could cause an abnormal heart rhythm, and even result in cardiovascular issues. Currently, the levels of electrolyte ions are measured using ion-selective electrodes. There is a need for alternative ion quantification systems for in-field applications because the current ion-selective electrodes can be difficult to use outside of a clinical setting as they are fragile, subject to biofouling, and can be expensive. We electrodeposited Prussian blue on a screen-printed electrode for our first platform. Prussian blue has been previously reported as a sensing layer for potassium and sodium ions on platinum, alumina, and nanotubes [2], as well as on pencil graphite electrodes [3]. The measured shift of potential of the redox peak indicates the presence of the analyte, which is a result of the intercalation of the targeted ion in the electrodeposited layer. Using a screen-printed electrode, we tested a solution containing potassium ions and compared it to a similar solution containing magnesium ions. We also measured the potential shifts in the presence of sodium ions. The solution of potassium ions displayed a significant shift of the potential of the oxidative peak of Prussian blue when compared to the other two electrolytes. We are quantifying potassium as a proof-of-concept of a novel electrochemical micronutrient sensing system. Paper-based sensing platforms are very useful for resource-limited settings and field testing due to advantages such as simplicity, low cost, portability and disposability [4]. By developing an accurate, portable ion-sensing paper-based platform, we will provide a more rapid and versatile alternative to current ion-selective electrode devices. Future work includes the development of a panel of multiplexed systems with various sensing layers allowing for the detection and quantification of different clinically useful ions. References 1) Alexander Kratz, M. F., Patrick M. Sluss, Kent B. Lewandrowski (2004). "Normal Reference Laboratory Values." The New England Journal of Medicine 351: 1548-1563. 2) Kuo-Chuan Ho, C.-L. L. (2001). "A Novel Potassium Ion Sensing Based on Prussian Blue Thin Films." Sensors and Actuators B: Chemical 76: 512-518. 3) Jin Qiang Ang1, B. T. T. N., Chee-Seng Toh (2011). "A dual K+–Na+ selective Prussian blue nanotubes sensor." Sensors and Actuators B: Chemical 157(2): 417-423. 4) Wen-Jie Lan, X. U. Z., Mahiar M. Hamedi, Jinbo Hu, Claudio Parolo, E. Jane Maxwell, Philippe Buhlmann, George M. Whitesides (2014). "Paper-Based Potentiometric Ion Sensing." Analytical Chemistry 86: 9548-9553. Figure 1

Prussian blue hollow nanostructures: Sacrificial template synthesis and application in hydrogen peroxide sensing

A facile sacrificial template method was developed for the controlled synthesis of Prussian blue (PB) hollow nanostructures. The hollow nanostructures can either be hollow nanospheres or nanotubes by controlling the shape of the sacrificial template. The morphology, structure and composition of the as-prepared PB hollow nanostructures were characterized by transmission electron microscopy, scanning electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy and ultraviolet–visible absorption spectroscopy. The results showed that the PB hollow nanostructures had complementary shapes and sizes of the original sacrificial templates. In addition, PB hollow nanostructures were immobilized on the surface of glassy carbon electrode and applied to detect hydrogen peroxide. Cyclic voltammograms showed that the PB nanotubes kept their intrinsic electrochemical properties, and possessed prominent electrocatalytic activity toward the reduction of hydrogen peroxide. This approach can be extended to synthesize the other PB analogues for the applications in high-performance bioelectronic devices and biosensors.

Fuel Cell Virus Sensor Using Virus Capture within Antibody-Coated Nanochannels

We report a unique fuel cell sensor system for the first time direct detection of unlabeled virus particles based on the formation of antibody-virus complexes within the sensor's membrane nanochannels. This strategy exploits the change in the membrane resistance of the powered system, comprising a Prussian blue nanotubes (PB-nt) membrane cathode and a platinum mesh anode. The method reports an impressive shortest response time of ∼5 min toward the specific virus target, at low concentration values of 3-45 plaque-forming units per milliliter (pfu mL(-1)) with detection limit of 0.04 pfu mL(-1), comparable to state-of-the-art polymerase chain reaction (PCR)-based methods. The sensor can clearly differentiate dengue virus serotype 2 from serotype 3. When filled with Nafion perfluorinated resin, the PB-nt membrane demonstrates powerful utilization as a stand-alone fuel cell based virus sensor, and thus offers the outstanding promise of a sustainable, low-cost, and rapid low-power virus detection tool.

Self-powering amperometric sensor and biosensor

A unique Prussian blue nanotubes sensor using a two-compartment cell derives the current signal from the chemical energy of the hydrogen peroxide analyte, without input of electrical potentials, is described. The Prussian blue reduces hydrogen peroxide and is itself reduced by electron flow from the counter reaction at the auxiliary electrode. The concentrations of the Prussian blue (PB) and Everitt’s salt (ES) forms of the Prussian blue are maintained at steady-state values, by the hydrogen peroxide reduction and the galvanic cell reaction. This strategy gives low detection limit of 0.1μM H2O2 with linear range up to 80μM and is further demonstrated in a model glucose biosensor. The simple design to reduce energy usage opens up the study of amperometric sensor development by selecting anodic and cathodic reactions with suitable thermodynamic potentials with consideration of reactions at the sensing and auxiliary electrodes modified with appropriate mediators or enzymes.

A dual K +–Na + selective Prussian blue nanotubes sensor

A strategy for dual sensing of Na + and K + ions using Prussian blue nanotubes via selective inter/deintercalation of K + ion and competitive inhibition by Na + ion, is reported. The analytical signal is derived from the cyclic voltammetry cathodic peak position E pc of Prussian blue nanotubes. Na + and K + levels in a sample solution can be determined conveniently using one Prussian blue nanotubes sensor. In addition, this versatile method can be applied for the analysis of single type of either Na + or K + ions. The dual-ion sensor response towards Na + and K + can be described using a model based on the competitive inhibition effects of Na + on K + inter/deintercalation in Prussian blue nanotubes. Successful application of the Prussian blue nanotubes sensor for Na + and K + determination is demonstrated in artificial saliva.

Ion-selective detection of non-intercalating Na + using competitive inhibition of K + intercalation in Prussian blue nanotubes sensor

A nanotubes sensor for Na + is fabricated using electrodeposition of iron hexacyanoferrate polymer within the nanochannels of a nanoporous metal-coated membrane. The sensing signal is derived from the influence of Na + on the cathodic peak potential of the voltammetric response of the Prussian blue (PB) nanotubes immersed in a background solution containing K +, giving a 2K +:1e − Nernstian response, instead of the usual 1K +:1e − process in the absence of Na +. A competitive-inhibition reaction scheme is proposed which gives excellent agreement of theoretical values derived from equilibrium consideration, with experimental data obtained under reversible, slow scan rate conditions. A wide linear range over three orders of magnitude for Na sensing can be achieved by simple adjustment of background K + levels. Specific and accurate detection of Na + using the PB nanotubes sensor is demonstrated in a solution containing potential interfering ions: K +, Mg 2+, Ca 2+.

Sensitive detection of potassium ion using Prussian blue nanotube sensor

A model K + sensor using Prussian blue nanotubes is fabricated by electrochemical deposition of Prussian blue (PB) within the nanochannels of a porous metal-coated membrane with partially covered pore openings. The PB nanotube sensor exhibits excellent stability giving reproducible peak potentials up to 500 measurement cycles, a very low detection limit of 2.0 × 10 −8 M and extremely wide logarithmic linear ranges between 5.0 × 10 −8–7.0 × 10 −4 M and 7.0 × 10 −4–1.0 M. Negligible interferences by Na +, Mg 2+ and Ca 2+ are observed and a rapid analysis time of 30 s is readily achieved. The ease of electrodeposition, high stability of PB nanotubes and outstanding analytical performance which surpasses conventional PB voltammetric and potentiometric sensors demonstrates potential sensing applications including ion sensors and biosensors using PB and other metal hexacyanoferrate nanotubes.

Nano-patterned liquid metal electrode for the synthesis of novel Prussian blue nanotubesand nanowires

We report the fabrication of Prussian blue nanotubes and nanowires via a novel techniquewherein a liquid metal surface is nano-patterned with a porous polycarbonate membraneused as a hard mask. Prussian blue as 1D nanowires and nanotubes is an excellentcandidate for ultra-low level sensing, optical waveguides and model systems to test theone-dimensional Ising model. One of the most feasible techniques for nanowire fabricationis to use a porous template. However, Prussian blue dissolves in strong acids anddecomposes in strong bases. Conventional procedures which use porous alumina blockedwith a back side metal contact require strong acid and base treatment in the varioussteps of the nanowire fabrication. We report a novel technique which will pave anew route for the facile synthesis of nanowires and nanotubes of materials thatare sensitive to strong acidic or basic treatment. Hence, nano-patterning of aliquid metal (Hg, which functions as a top-side metal contact) with polycarbonatemembrane instead of porous alumina membrane excludes the necessity of both strongacid and base during the fabrication of nanowires. By attempting this innovativetechnique, we report the synthesis of novel organic Prussian blue nanotubes andnanowires.

Fabrication of High-Aspect-Ratio Prussian Blue Nanotubes Using a Porous Alumina Template

Prussian blue nanotubes were fabricated by using a sequential deposition technique inside the 60-nm well-ordered pores of anodic alumina. By varying the deposition parameters and the dimensions of the template, we could tailor the length and the outer as well as the inner diameter of the tubes. The nanotubes were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD).