Dominick J. Casadonte

Frequency effect on the sonochemical remediation of alachlor.

The effect of ultrasonic frequency on the sonodegradation of alachlor is described. The rate observed for the destruction of alachlor is approximately 25 times faster at 300 kHz under argon saturation than at 20 kHz under comparable acoustic input energy. The effect of variation of a number of extrinsic parameters such as dissolved gases, radical scavengers and hydroxyl radical promoters is also explored. Argon-saturated solutions display an enhancement in rate by a factor of two compared to either oxygen- or air-saturated solutions upon sonication at 300 kHz. The principal ultrasonic degradation products have been determined in air, argon, and oxygen. The products results primarily from cleavage of the N-methoxymethyl unit when sonication occurs in argon and air. Oxygen addition has been observed when the saturating gas is oxygen. The nature of the active site for reactivity of alachlor is discussed.

Design and calibration of a single-transducer variable-frequency sonication system.

The design of a novel single-transducer variable-frequency sonication system capable of operating at constant acoustic power over the range 20-500 kHz is described. The system employs a mass-loaded sandwich transducer arrangement and a series of transformers to provide an accurate impedance matching circuit. Approximately 0-5 W of acoustic power are produced by the system at typical operating frequencies of 20, 40, 150, 200, 300, and 450 kHz. As a first test of the single-transducer variable-sonication system we have re-examined the frequency dependence of the sonochemical oxidation of potassium iodide. Previous investigators have monitored the frequency dependence using a multi-transducer system to obtain the different frequencies required. In accordance with the earlier findings, we have observed an eightfold increase in the rate of potassium iodide oxidation at 300 kHz compared to 20 kHz, as well as an inversion in the rate of oxidation for argon and air-saturated solutions at 300 kHz. Possible reasons for the rate variations are discussed.

Synthesis of PtCu3 bimetallic nanoparticles as oxygen reduction catalysts via a sonochemical method

We report a sonochemical synthesis of homogeneous PtCu3 nanoparticles. Ultra-sonication during reduction in a non-aqueous solution is compared with synthesis under identical conditions in the absence of sonication (to form a Rieke alloy). X-ray diffraction (XRD) measurements suggest that the sonochemical procedure produces an amorphous, uniformly alloyed nanomaterial having a composition consistent with the PtCu3 stoichiometry, while the Rieke alloy is polyphasic. Energy dispersive X-ray (EDX) analysis indicates that the composition of the sonochemically prepared PtCu3 material reflects the nominal values. EDX and XRD analyses also provide evidence for the inhibition of oxide formation on sonochemically prepared PtCu3 nanoparticles, but oxide is readily apparent in the Rieke alloy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the sonochemically prepared sample show particles with diameters of ∼2 to 3 nm. As-synthesized PtCu3 particles were activated using an electrochemical de-alloying procedure to prepare an oxygen reduction electrocatalyst. The de-alloyed catalyst consisted of a Pt-rich surface layer, over a core indicated as having a Pt3Cu composition. The de-alloyed sample exhibited ∼3 to 6 fold enhancements in oxygen reduction reaction (ORR) activity when compared to commercial Pt catalysts.

Structural analysis of sonochemically prepared PtRu versus Johnson Matthey PtRu in operating direct methanol fuel cells

Sonochemically prepared PtRu (3 : 1) and Johnson Matthey PtRu (1 : 1) were analyzed by X-ray absorption spectroscopy in operating liquid feed direct methanol fuel cells. The total metal loadings were 4 mg cm(-2) unsupported catalysts at the anode and cathode of the membrane electrode assembly. Ex situ XRD lattice parameter analysis indicates partial segregation of the Ru from the PtRu fcc alloy in both catalysts. A comparison of the in situ DMFC EXAFS to that of the as-received catalyst shows that catalyst restructuring during DMFC operation increases the total metal coordination numbers. A combined analysis of XRD determined grain sizes and lattice parameters, ex situ and in situ EXAFS analysis, and XRF of the as-received catalysts enables determination of the catalyst shell composition. The multi-spectrum analysis shows that the core size increases during DMFC operation by reduction of Pt oxides and incorporation of Pt into the core. This increases the mole fraction of Ru in the catalyst shell structure.

Sonochemical synthesis of iron phosphide.

The sonochemical reaction of Fe(CO)5 and triethylphosphine has been found to produce solid amorphous iron phosphide of composition FeP. The resulting compound was characterized by elemental microanalysis, scanning electron microscopy, energy-dispersive X-ray analysis, and Debye-Scherrer powder X-ray diffraction. X-ray powder patterns were obtained after the amorphous material had been heated above 950 degrees C and then slowly cooled to induce crystallization. This reaction provides the first use of ultrasound to sonochemically synthesize amorphous phosphide semiconductor materials from organometallic precursors.

The use of pulsed ultrasound technology to improve environmental remediation: a comparative study.

Relatively little is known about the effects of pulsed ultrasound on the facilitation of chemical reactivity and remediation. Previous studies have indicated that sonochemistry using pulses may be either more or less effective than continuous wave (CW) ultrasonic irradiation. However, because of the time-modulated nature of the pulses used in these studies, less acoustic energy in general was transmitted to the solutions compared to CW sonication. The effectiveness of ultrasound when the pulse is adjusted so that the same amount of acoustic energy is input compared to continuous irradiation over a given time has not been previously explored. In this study we have embarked on a comparison of the efficacy of power-modulated pulsed (PMP) sonochemistry with more traditional time-modulated pulsing. As a prototypical reaction, we have explored the effects of pulse type on the degradation of acid orange, a common industrial colorant. An increase in the degradation rate by a factor of three was observed using PMP ultrasound compared with continuous irradiation under conditions of equivalent acoustic input power, while the use of time-modulated pulsed ultrasound from a commercially available direct-immersion (DI) horn-type sonicator exhibited a rate decrease compared to CW sonication. Possible mechanisms for the enhancement are discussed.

Forensic identification of pharmaceuticals via portable X-ray fluorescence and diffuse reflectance spectroscopy

The importance of unknown substance identification in forensic science is vital to implementation or exclusion of criminal charges against an offender. While traditional laboratory measures include the use of gas chromatography/mass spectroscopy, an alternate method has been proposed to efficiently perform presumptive analyses of unknown substances at a crime scene or at airport security points. The use of portable X-ray fluorescence (PXRF) and visible near infrared diffuse reflectance spectroscopy (DRS) to determine elemental composition was applied to pharmaceutical medications (n=83), which were then categorized into 21 classifications based on their active ingredients. Each pharmaceutical was processed by standard laboratory procedures and scanned with both PXRF and DRS. Lastly, the datasets obtained were compared using multivariate statistical analyses. The aforementioned devices indicate that differentiation of unknown substances is clearly demonstrated among the samples with 73.49% DRS classification accuracy. Thus, the approach shows promise for future development as a rapid analytical technique for unknown pharmaceutical substances and/or illicit narcotics.

Work in progress — Classroom and distance components of a GK12 program placing graduate students in high school classrooms

As our national mathematics and science scores continue to fall below expectations, creating environments that engage the professional scientific and engineering communities in public education becomes increasingly important. Most mathematics and science teachers in high schools do not have a professional background in mathematics, science, or engineering (STEM) fields; thus, students in the public education system rarely interact with STEM professionals, and know little about the opportunities for careers in these fields. The NSF GK12 program supports graduate students who spend time in K12 classrooms for the purposes of learning to share their research with a nontechnical community. In year 3 of this specific GK12 program, a distance component was implemented by placing the graduate student in the classroom, virtually, through online streaming video. This paper discusses the technology, both hardware and software, that is used in this arrangement, as well as the challenges associated with implementing the technology in the school. This paper also describes the approach taken in designing and deploying an interdisciplinary learning module via distance. Finally, the paper describes the plans for continued distance components of the program.