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Phosphorus is required for plants and humans to survive because it is needed for cell signaling, skeletal integrity, energy storage and metabolism. Phosphorus measurements are performed using colorimetric and electrochemical methods. Colorimetry is the most accepted method for commercial devices for phosphorus monitoring while electrochemical systems are still in the research phase. Here we provide the first comprehensive review of solid-state sensors for phosphate monitoring. The review focuses on solid state reagent storage for colorimetric sensors and different materials used in solid state electrochemical sensors. The electrochemical sensors are further classified into three groups: potentiometric, amperometric and voltammetric. All sensors are evaluated based on parameters such as measurement range, limit of detection (LOD), working pH and response time. Finally, we discuss limitations of the current sensors and future directions for the development of these sensors. [ABSTRACT FROM AUTHOR]

Palladium nanomaterials have shown great promise for use in sensing and energy storage devices, and developing simple and inexpensive top-down and bottom-up methods for creating such materials has attracted much attention. In spite of tremendous progress in recent years, creating hierarchical multiscale materials which are dually optimized at the nanoscale for addressing various functional demands and are amenable for micro/macroscale integration into practical devices, remains a challenge. Here we demonstrate a rapid and simple approach based on kinetically-controlled electrochemical deposition and photolithography for creating programmable hierarchical multiscale palladium structures. Through electrochemical methods, we are able to structurally and functionally program palladium materials based on their deposition kinetics. Structures ranging from 2D thin films into 3D globules decorated with nano-needles are created with a tunable hydrogen storage capacity. Raman signal magnitude, and analytical sensitivity. Furthermore, lithography-based methods are used to pattern these programmable structures into highly organized and periodic configurations. [ABSTRACT FROM AUTHOR]

The accuracy of many biological and chemical sensors is critically dependent on the stability of the potential imposed or sensed through a reference electrode. As these sensors are miniaturized, the reference electrode has to be miniaturized simultaneously without any loss to its stability. In this paper, we describe a new microfluidic miniaturized silver/silver chloride reference electrode that demonstrates significantly better stability and lifetime than conventional designs. In our new design, we have miniaturized the existing format of the macroscale reference electrode and added the capability to replenish the internal solution by integrating it with a microfluidic channel. The replenishment of the internal solution significantly improves the performance of these electrodes over other miniaturized designs. We demonstrate reference electrodes that are very stable (potential variation of <0.1 mV), with minimal drift (~ I mV) and lifetimes longer than 100 hours. We have also characterized the behavior of these electrodes to changes in pH and chlorine concentration of the external solution. The results indicate insensitivity of the microfluidic reference electrode potential to the presence of any analyte in the test solution. [ABSTRACT FROM AUTHOR]