The world's oceans may absorb a large part of the C02 emissions generated by burning fossil fuels, thereby lessening the greenhouse effect. However, measuring this global process will require highly accurate, precise new chemical sensors that can operate unattended for long periods on buoys deployed at sea. This project will develop a fiber optical pH sensor and instrument package that does not require calibration with external standards and therefore can operate unattended. The inherently calibrated sensor is made possible by a proprietary process that produces thin, physically resilient transparent films of pH indicator dyes. Optical absorbance measurements made at multiple wavelengths will provide accurate (0.001 pH units) and precise pH measurements free from the drift displayed by conventional pH electrodes. Phase I will demonstrate that the immobilized dyes, because they have optical properties and acid/base chemistries that are similar to dyes in solution, are therefore capable of inherent calibration. Phase 11 will develop an instrument that can exploit the benefits of inherent calibration. The self-calibrating instrument will be constructed using low-power Composite Metal-Oxide Semiconductor technology on a circuit board that can be plugged into a personal computer (PC). Multiplexing will allow several pH sensors to use a single linear diode array detector. Internal shutdown software will schedule measurements around low current idle periods so that long-term, unattended operation on buoys at sea will be possible using solar trickle recharging of the power supply. The sensors and instrument package will allow oceanographers to deploy large numbers of sensors for extended periods and will provide the data necessary to measure oceans' response to anthropogenic inputs of C02.Anticipated Results/Potential Commercial Applications as described by the awardee:The inherently calibrated pH sensors and PC board-mounted optical instrument will give the highly accurate and precise data necessary for evaluating C02 flux into the oceans. More importantly, the technology will find direct and immediate application in the $100 million process control instrumentation industry. The pH sensors and PC plug-in instrument are ideally suited for control of bioreactors and fermentors. Unlike existing electrodes, inherently calibrated sensors can be sterilized without changing their calibration and can be left for long periods without drifting. The improved yields from better pH control of fermentations can be measured in the millions of dollars. The principle of inherent calibration can be applied to a wide array of chemical sensors.