LED-based screener for photoelectrochemical materials discovery
An LED-based materials analysis apparatus that measures the photoelectrochemical response of materials to illumination. The apparatus uses an array of light sources such as a plurality of LEDs that provide light of desired wavelengths to illuminate one or more samples of materials of interest that are immersed in an electrolyte. A measurement circuit is connected between a transparent conductor attached to each sample of interest and a counter electrode. In some measurements, a third, standard electrode may be connected to the measurement circuit. A pulsing circuit that operates the LEDs causes each sample to be tested according to a predetermined sequence. Data is collected using a programmable computer operating under the control of instructions recorded on a machine readable medium. The data is analyzed and is available to be displayed to a user, recorded in a database, or communicated to another apparatus or process.
1. An LED-based apparatus for measuring photoelectrically active materials, comprising:
a plurality of LEDs, said plurality of LEDs arranged in a spatially defined array, each of said plurality of LEDs configured to provide illumination having a desired range of wavelengths, each of said plurality of LEDs configured to illuminate a location in registry with said LED, each of said plurality of LEDs having two terminals, each of said plurality of LEDs configured to be individually addressed for the purpose of illuminating said plurality of locations in a predetermined sequence;
a pulsing circuit configured to generate an electrical pulse sufficient to operate a respective one of said plurality of LEDs, said pulsing circuit having a terminal configured to control an illumination current of said respective one of said plurality of LEDs at a controlled voltage and a terminal configured to be connected to a reference voltage, said pulsing circuit configured to be connected to said two terminals of each of said plurality of LEDs in said predetermined sequence;
an electrochemical cell configured to receive at least one specimen of interest, said specimen of interest comprising a material to be examined for electrochemical activity; said electrochemical cell comprising;
a transparent specimen holder configured to receive said at least one specimen of interest, said at least one specimen of interest positioned at a respective one of said locations in registry with a selected one of said plurality of LEDs, said transparent specimen holder having an electrically conductive surface configured to make electrical contact with said at least one specimen of interest, and having a specimen holder electrical contact terminal in electrical communication with said electrically conductive surface;
an electrolyte volume configured to contain an electrolyte; and
a counter electrode having a counter electrode electrical terminal, said transparent specimen holder, said electrolyte volume and said counter electrode configured to provide a cell in which a photoelectrochemical measurement of said at least one specimen of interest can be conducted;
a potentiostat configured to measure a photoelectrochemical signal generated in response to an illumination of a respective one of said locations in registry with said LED, said potentiostat connected to said specimen holder electrical contact terminal and to said counter electrode electrical terminal; and
a general purpose programmable computer having a set of instructions recorded on a machine-readable medium, said general purpose programmable computer configured to receive said photoelectrochemical signal, configured to analyze said photoelectrochemical signal to obtain a result, and configured to perform at least one of recording said photoelectrochemical signal, displaying said result to a user, and recording said result.
2. The LED-based apparatus for measuring photoelectrically active materials of claim 1 , wherein at least one of said plurality of LEDs is configured to provide white light illumination.
3. The LED-based apparatus for measuring photoelectrically active materials of claim 1 , wherein at least one of said plurality of LEDs is configured to provide colored light illumination.
4. The LED-based apparatus for measuring photoelectrically active materials of claim 3 , wherein at least one of said plurality of LEDs configured to provide colored light illumination includes an LED and a filter having a pass band.
5. The LED-based apparatus for measuring photoelectrically active materials of claim 1 , wherein said transparent specimen holder comprises a non-conductive transparent plate and a conductive transparent layer thereon.
6. The LED-based apparatus for measuring photoelectrically active materials of claim 1 , further comprising a reference electrode configured to be in contact with said electrolyte and configured to be electrically connected to said potentiostat.
7. The LED-based apparatus for measuring photoelectrically active materials of claim 1 , wherein said plurality of LEDs is disposed in an array having rows and columns.
8. The LED-based apparatus for measuring photoelectrically active materials of claim 1 , wherein said plurality of LEDs is disposed in an 8×8 array.
9. The LED-based apparatus for measuring photoelectrically active materials of claim 1 , wherein said plurality of LEDs comprises 2 N LEDs, where N is an integer greater than 0.