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Articles you may be interested inCdSe quantum dots-poly(3-hexylthiophene) nanocomposite sensors for selective chloroform vapor detection at room temperature Highly sensitive passive radio frequency identification based sensor systems Rev. Sci. Instrum. 81, 025106 (2010); 10.1063/1.3316804Metal-ferroelectric-metal capacitor based persistent memory for electronic product code class-1 generation-2 uhf passive radio-frequency identification tag Comparison of organic diode structures regarding high-frequency rectification behavior in radio-frequency identification tagsSelective vapor sensors are demonstrated that involve the combination of ͑1͒ organic electronic sensing materials with diverse response mechanisms to different vapors and ͑2͒ passive 13.56 MHz radio-frequency identification ͑RFID͒ sensors with multivariable signal transduction. Intrinsically conducting polymers such as poly͑3,4-ethylenedioxythiophene͒ and polyaniline ͑PANI͒ were applied onto resonant antennas of RFID sensors. These sensing materials are attractive to facilitate the critical evaluation of our sensing concept because they exhibit only partial vapor selectivity and have well understood diverse vapor response mechanisms. The impedance spectra Ž ͑f͒ of the RFID antennas were inductively acquired followed by spectral processing of their real Z re ͑f͒ and imaginary Z im ͑f͒ parts using principal components analysis. The typical measured 1 noise levels in frequency and impedance magnitude measurements were 60 Hz and 0.025 ⍀, respectively. These low noise levels and the high sensitivity of the resonant RFID sensor structures resulted in NH 3 determinations with the 3 detection limit down to 20 ppb. This achieved detection limit was 25-50-fold better over chemoresistor sensors based on PANI films and nanowires.

Optoelectronic consumer products that are widely employed in the office and home attract attention for optical sensor applications due to (1) their cost advantage over analytical instruments produced only in small quantities, (2) robustness in operation due to the detailed manufacturability improvements, and (3) ease of operation. We demonstrate here a new approach for quantitative chemical/biochemical sensing when analog signals are acquired from conventional optical disk drives, and these signals are used for quantitative detection of optical changes of sensor films deposited on conventional CD and DVD optical disks. Because we do not alter manufacturing process of optical disks, any disk can be employed for deposition and readout of sensor films. The optical disk drives also perform their original function of reading and writing digital content to optical media because no optical modifications are introduced to obtain the analog signal. Such a sensor platform is quite universal and can be applied for chemical and biological quantitative detection, as well as for monitoring of changes of physical properties of regions deposited onto a CD or DVD (e.g., during combinatorial screening of materials). As a model example, we demonstrate the concept using chemical detection of ionic species such as Ca2+ in liquids (e.g., blood, urine, or water). Colorimetric calcium-sensitive sensor films were deposited onto a DVD, exposed to water with different concentrations of Ca2+, and quantified in the optical disk drive. The developed lab-on-DVD system demonstrated a 5 ppm detection limit of Ca2+ determinations, similar or slightly better than that achieved using a conventional fiber-optic portable spectrometer. This detection limit corresponded to a 0.023 absorbance unit resolution, as determined by the measurement of the same colorimetric films with a portable spectrometer. Determinations of Ca2+ unknowns using the lab-on-DVD system demonstrated +/-5 ppm accuracy and 2-5% relative standard deviation precision in predicting 100 ppm Ca2+.

Passive radio frequency identification (RFID) sensors are attractive in diverse applications where sensor performance is needed at a low cost and when battery-free operation is critical. We developed a general approach for adapting ubiquitous and cost-effective passive 13.56-MHz RFID tags for diverse sensing applications. In developed RFID sensors, the complex impedance of the RFID resonant antenna is measured and correlated to physical, chemical, or biological properties of interest. In contrast to known wireless sensors, developed RFID sensors combine several measured parameters from the resonant sensor antenna with multivariate data analysis and deliver unique capability for multianalyte sensing and rejection of environmental interferences with a single sensor. Theoretical calculations and experiments in an anechoic chamber demonstrate that the developed RFID sensors are immune to common electromagnetic interferences and the sensor/reader system operates within regulated emission levels. Performance of developed RFID sensors is illustrated in measurements of toxic industrial chemicals (TICs) in air with the detection limit (DL) of 80 parts per billion and in a non-invasive monitoring of milk spoilage. Sensors selectivity is demonstrated in the detection of different vapors with individual sensors. designs such as resonant inductor-capacitor [1,2], magnetoelastic [3], thickness shear mode [4], and surface-acoustic wave [5,6] transducers. Examples of detected physical parameters using these sensors Fig. 9. Results of extended-length experiment of the response of the RFID sensor for toxic volatile polar and nonpolar vapors TCE, MeOH, and Tol. (A) Sensor exposure to four replicate sets of 0-0.20 P/Po concentrations of three tested vapors. (B) Rapid response and recovery times of the sensor to three tested vapors. Insets show the response and recovery times of less than 1 min for 0.04 P/Po of TCE, MEOH, and Tol.