Photothermal induced resonance (PTIR) has recently attracted great interest for enabling chemical identification and imaging with nanoscale resolution. In this work, electron beam nanopatterned ...polymer samples are fabricated directly on 3D zinc selenide prisms and used to experimentally evaluate the PTIR lateral resolution, sensitivity and linearity. It is shown that PTIR lateral resolution for chemical imaging is comparable to the lateral resolution obtained in the atomic force microscopy height images, up to the smallest feature measured (100 nm). Spectra and chemical maps are produced from the thinnest sample analyzed (40 nm). More importantly, experiments show for the first time that the PTIR signal increases linearly with thickness for samples up to ≈ 1 μm (linearity limit); a necessary requirement towards the use of the PTIR technique for quantitative chemical analysis at the nanoscale. Finally, the analysis of thicker samples provides the first evidence that the previously developed PTIR signal generation theory is correct. It is believed that the findings of this work will foster nanotechnology development in disparate applications by proving the basis for quantitative chemical analysis with nanoscale resolution.
Quantitative chemical imaging with nanoscale resolution is demonstrated using a photothermal induced resonance technique by measuring the sample thermal expansion induced by the absorption of IR light with an atomic force microscopy tip. Lateral resolution, sensitivity, and linearity of the technique is evaluated with lithographically defined samples.
The atomic force microscope (AFM) offers a rich observation window on the nanoscale, yet many dynamic phenomena are too fast and too weak for direct AFM detection. Integrated cavity-optomechanics is ...revolutionizing micromechanical sensing; however, it has not yet impacted AFM. Here, we make a groundbreaking advance by fabricating picogram-scale probes integrated with photonic resonators to realize functional AFM detection that achieve high temporal resolution (<10 ns) and picometer vertical displacement uncertainty simultaneously. The ability to capture fast events with high precision is leveraged to measure the thermal conductivity (η), for the first time, concurrently with chemical composition at the nanoscale in photothermal induced resonance experiments. The intrinsic η of metal–organic-framework individual microcrystals, not measurable by macroscale techniques, is obtained with a small measurement uncertainty (8%). The improved sensitivity (50×) increases the measurement throughput 2500-fold and enables chemical composition measurement of molecular monolayer-thin samples. Our paradigm-shifting photonic readout for small probes breaks the common trade-off between AFM measurement precision and ability to capture transient events, thus transforming the ability to observe nanoscale dynamics in materials.
The photon-drag effect, the rectified current in a medium induced by conservation of momentum of absorbed or redirected light, is a unique probe of the detailed mechanisms underlying radiation ...pressure. We revisit this effect in gold, a canonical Drude metal. We discover that the signal for p-polarized illumination in ambient air is affected in both sign and magnitude by adsorbed molecules, opening previous measurements for reinterpretation. Further, we show that the intrinsic sign of the photon-drag effect is contrary to the prevailing intuitive model of direct momentum transfer to free electrons.
Multiphoton polymer cross-linking evolves as the core process behind high-resolution additive microfabrication with soft materials for implantable/wearable electronics, tissue engineering, ...microrobotics, biosensing, drug delivery, etc. Electrons and soft X-rays, in principle, can offer even higher resolution and printing rates. However, these powerful lithographic tools are difficult to apply to vacuum incompatible liquid precursor solutions used in continuous additive fabrication. In this work, using biocompatible hydrogel as a model soft material, we demonstrate high-resolution in-liquid polymer cross-linking using scanning electron and X-ray microscopes. The approach augments the existing solid-state electron/X-ray lithography and beam-induced deposition techniques with a wider class of possible chemical reactions, precursors, and functionalities. We discuss the focused beam cross-linking mechanism, the factors affecting the ultimate feature size, and layer-by-layer printing possibilities. The potential of this technology is demonstrated on a few practically important applications such as in-liquid encapsulation of nanoparticles for plasmonic sensing and interfacing of viable cells with hydrogel electrodes.
Gods in the Desert explores the fascinating religious cultures of the ancient Near East. From the mysterious pyramids, tombs, and temples of Egypt to the powerful heroes, gods, and legends of ...Mesopotamia, Glenn Holland guides readers through the early religions that are the root of many of today's major faiths. Holland compares the religions of ancient Egypt, Mesopotamia, and Syria-Palestine, including Israel and Judah, from the Neolithic era through the conquest of Alexander the Great. He provides a historical survey of each region, then discusses the gods, the rulers, the afterlife, and the worship rituals. This accessible overview makes clear how these religions converged and diverged, and are intimately connected to many of the religions we recognize today, sometimes in surprising ways.
Background & Aims Polymorphisms in brain-derived neurotrophic factor (BDNF) can affect brain and behavioral responses. However, little is known about the effects of a single nucleotide polymorphism ...(SNP) in BDNF , at codon 66 (the Val−Met substitution, detected in approximately 33% of the Caucasian population) on stimulation-induced plasticity in the cortico-bulbar system. We examined whether this SNP influenced outcomes of different forms of neurostimulation applied to the pharyngeal motor cortex. Methods Thirty-eight healthy volunteers were assessed for corticobulbar excitability after single-pulse, transcranial magnetic stimulation of induced pharyngeal electromyographic responses, recorded from a swallowed intraluminal catheter. Thereafter, volunteers were conditioned with pharyngeal electrical stimulation, or 2 forms of repetitive (1 and 5 Hz) transcranial magnetic stimulation (rTMS). Repeated measurements of pharyngeal motor-evoked potentials were assessed with transcranial magnetic stimulation for as long as 1 hour after the 3 forms of neurostimulation and correlated with SNPs at codon 66 of BDNF (encoding Val or Met). Results Pharyngeal electrical stimulation significantly increased the amplitude of motor-evoked potentials in individuals with the SNP that encoded Val66, compared to those that encoded Met66, with a strong GENOTYPE*TIME interaction ( F8,112 = 2.4; P = .018). By contrast, there was a significant reduction in latencies of subjects with the SNP that encoded Met66 after 5-Hz rTMS ( F3,60 = 4.9; P = .04). In addition, the expected inhibitory effect of 1-Hz rTMS on amplitude was not observed in subjects with the SNP that encoded Met66 in BDNF ( F7,140 = 2.23; P = .035). Conclusions An SNP in human BDNF at codon 66 affects plasticity of the pharyngeal cortex to different forms of neurostimulation. Genetic analysis might help select specific forms of neurostimulation as therapeutics for patients with disorders such as dysphagic stroke.
The collective oscillation of conduction electrons, responsible for the localized surface plasmon resonances, enables engineering nanomaterials by tuning their optical response from the visible to ...terahertz as a function of nanostructure size, shape, and environment. While theoretical calculations helped tremendously in understanding plasmonic nanomaterials and optimizing their light matter interaction, only a few experimental techniques are available to study these materials with high spatial resolution. In this work, the photothermal-induced resonance (PTIR) technique is applied for the first time to image the dark plasmonic resonance of gold asymmetric split ring resonators (A-SRRs) in the mid-infrared (IR) spectral region with nanoscale resolution. Additionally, the chemically specific PTIR signal is used to map the local absorption enhancement of poly(methyl methacrylate) coated on A-SRRs, revealing hot spots with local enhancement factors up to ≈30 at 100 nm lateral resolution. We argue that PTIR nanoscale characterization will facilitate the engineering and application of plasmonic nanomaterials for mid-IR applications.
Absorption spectroscopy and mapping from visible through mid-IR wavelengths has been achieved with spatial resolution exceeding the limit imposed by diffraction via the photothermal induced resonance ...technique. Correlated vibrational (chemical), and electronic properties are obtained simultaneously with topography with a wavelength-independent resolution of ≈20 nm using a single laboratory-scale instrument. This marks the highest resolution reported for PTIR, as determined by comparing height and PTIR images, and its first extension to near-IR and visible wavelengths.
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