Monitoring Chemical Reactions with Terahertz Rotational Spectroscopy

Rotational spectroscopy is introduced as a new in situ method for monitoring gas-phase reactants and products during chemical reactions. Exploiting its unambiguous molecular recognition specificity and extraordinary detection sensitivity, rotational spectroscopy at terahertz frequencies was used to monitor the decomposition of carbonyl sulfide (OCS) over an aluminum nanocrystal (AlNC) plasmonic photocatalyst. The intrinsic surface oxide on AlNCs is discovered to have a large number of strongly basic sites that are effective for mediating OCS decomposition. Spectroscopic monitoring revealed two different photothermal decomposition pathways for OCS, depending on the absence or presence of H_2O. The strength of rotational spectroscopy is witnessed through its ability to detect and distinguish isotopologues of the same mass from an unlabeled OCS precursor at concentrations of <1 nanomolar or partial pressures of <10 μTorr. These attributes recommend rotational spectroscopy as a compelling alternative for monitoring gas-phase chemical reactants and products in real time

Exploiting Anisotropy of Plasmonic Nanostructures with Polarization-Modulation Infrared Linear Dichroism Microscopy (μPM-IRLD).

Metallic nanostructures that exhibit plasmon resonances in the mid-infrared range are of particular interest for a variety of optical processes where the infrared excitation and/or emission could be enhanced. This plasmon-mediated enhancement can potentially be used towards highly sensitive detection of an analyte(s) by techniques such as surface-enhanced infrared absorption (SEIRA). To maximize the SEIRA enhancement, it is necessary to prepare highly tuned plasmonic resonances over a defined spectral range that can span over several microns. Noteworthy, nanostructures with anisotropic shapes exhibit multiple resonances that can be exploited by controlling the polarization of the input light. This study demonstrates the role of polarization-modulation infrared linear dichroism coupled to microscopy measurements (μPM-IRLD) as a powerful means to explore the optical properties of anisotropic nanostructures. Quantitative μPM-IRLD measurements were conducted on a 2 series of dendritic fractals as model structures to explore the role of structural anisotropy on the resulting surface-enhanced infrared absorption and sensing application. Once functionalized with an analyte, the μPM-IRLD SEIRA results highlight that it is possible to selectively enhance further vibrational modes of analytes making use of the structural anisotropy of the metallic nanostructure

Self -esteem, self -compassion, defensive self -esteem, and related features of narcissism as predictors of aggression

This study sought to expand upon existing literature pertaining to feelings toward oneself and aggressive behavior. Specifically, global self-esteem, as well as two specific subsets of self-esteem, defensive self-esteem and narcissistic self-esteem, were examined as predictors of aggressive behavior. Additionally, the relationship between aggression and self-compassion, a recently introduced self-construct moderately correlated with self-esteem, was investigated. College students from a large Northeastern University were invited via email or through a brief classroom presentation to participate in this online study. A total of 181 students completed five surveys that were useable for data analyses: Rosenberg Self-Esteem Scale (SES; Rosenberg, 1989), Self-compassion Scale (SCS; Neff, 2003), Narcissistic Personality Inventory (NPI; Raskin & Terry, 1988), Marlowe-Crowne Social Desirability Scale (MCSD; Crowne & Marlowe, 1960), and Aggression Questionnaire (AQ; Buss & Warren, 2000). A series of hierarchical regression analyses were used to determine if aggressive behavior varied as a function of self-esteem, self-compassion, narcissism, and defensive self-esteem. Findings revealed that there was a positive relationship between global self-esteem and aggression, such that it accounted for 11.4% of the variance. When self-compassion was entered into the equation, results indicated that self-compassion had a unique contribution to aggression, accounting for 4.3% additional variance. This relationship was inverse, revealing that higher levels of self-compassion predicted lower levels of aggressive behavior. Defensive self-esteem was unexpectedly found to be related to lower levels of self-esteem, whereas narcissistic self-esteem and narcissism and self-compassion were not significant predictors. Findings suggest teaching self-compassionate skills could be a useful component of comprehensive interventions intended to decrease the occurrence of aggression

Fractal Nanoparticle Plasmonics: The Cayley Tree

There has been strong, ongoing interest over the past decade in developing strategies to design and engineer materials with tailored optical properties. Fractal-like nanoparticles and films have long been known to possess a remarkably broad-band optical response and are potential nanoscale components for realizing spectrum-spanning optical effects. Here we examine the role of self-similarity in a fractal geometry for the design of plasmon line shapes. By computing and fabricating simple Cayley tree nanostructures of increasing fractal order <i>N</i>, we are able to identify the principle behind how the multimodal plasmon spectrum of this system develops as the fractal order is increased. With increasing <i>N</i>, the fractal structure acquires an increasing number of modes with certain degeneracies: these modes correspond to plasmon oscillations on the different length scales inside a fractal. As a result, fractals with large <i>N</i> exhibit broad, multipeaked spectra from plasmons with large degeneracy numbers. The Cayley tree serves as an example of a more general, fractal-based route for the design of structures and media with highly complex optical line shapes

Charge Transfer Plasmons: Optical Frequency Conductances and Tunable Infrared Resonances

A charge transfer plasmon (CTP) appears when an optical-frequency conductive pathway between two metallic nanoparticles is established, enabling the transfer of charge between nanoparticles when the plasmon is excited. Here we investigate the properties of the CTP in a nanowire-bridged dimer geometry. Varying the junction geometry controls its conductance, which modifies the resonance energies and scattering intensities of the CTP while also altering the other plasmon modes of the nanostructure. Reducing the junction conductance shifts this resonance to substantially lower energies in the near- and mid-infrared regions of the spectrum. The CTP offers both a high-information probe of optical frequency conductances in nanoscale junctions and a new, unique approach to controllably engineering tunable plasmon modes at infrared wavelengths

Monitoring Chemical Reactions with Terahertz Rotational Spectroscopy

Rotational spectroscopy is introduced as a new <i>in situ</i> method for monitoring gas-phase reactants and products during chemical reactions. Exploiting its unambiguous molecular recognition specificity and extraordinary detection sensitivity, rotational spectroscopy at terahertz frequencies was used to monitor the decomposition of carbonyl sulfide (OCS) over an aluminum nanocrystal (AlNC) plasmonic photocatalyst. The intrinsic surface oxide on AlNCs is discovered to have a large number of strongly basic sites that are effective for mediating OCS decomposition. Spectroscopic monitoring revealed two different photothermal decomposition pathways for OCS, depending on the absence or presence of H₂O. The strength of rotational spectroscopy is witnessed through its ability to detect and distinguish isotopologues of the same mass from an unlabeled OCS precursor at concentrations of <1 nanomolar or partial pressures of <10 μTorr. These attributes recommend rotational spectroscopy as a compelling alternative for monitoring gas-phase chemical reactants and products in real time