Nanofibrils play a pivotal role in spider silk and are responsible for many of the impressive properties of this unique natural material. However, little is known about the internal structure of these protein fibrils. We carry out polarized Raman and polarized Fourier-transform infrared spectroscopies on native spider silk nanofibrils and determine the concentrations of six distinct protein secondary structures, including β-sheets, and two types of helical structures, for which we also determine orientation distributions. Our advancements in peak assignments are in full agreement with the published silk vibrational spectroscopy literature. We further corroborate our findings with X-ray diffraction and magic-angle spinning nuclear magnetic resonance experiments. Based on the latter and on polypeptide Raman spectra, we assess the role of key amino acids in different secondary structures. For the recluse spider we develop a highly detailed structural model, featuring seven levels of structural hierarchy. The approaches we develop are directly applicable to other proteinaceous materials.

Nonuniform strain on multilayer transition-metal dichalcogenide (TMDC) nanosheets is an exciting path toward practical optoelectronic devices, as it combines the advantages of localized control of optical and electronic properties with ease of fabrication. However, the weaker photoluminescence (PL) due to their indirect nature poses a challenge to their application. Here, we demonstrate extraordinary enhancement of PL from multilayer MoS2 nanosheets under nonuniform strain generated by nanopillars. We observe charge and exciton funneling to the pillar strain apex. The screening from the increased exciton and charge density lowers the exciton binding energy and renormalizes the band gap. Hence, we attribute the dramatic increase in PL to dissociation of bound excitons to free electron–hole pairs, showing that nonuniform strain on TMDC nanosheets can effectively manipulate the nature of light–matter interaction in these atomically thin materials for application in novel strain-engineered optoelectronics.

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Recent breakthroughs in material development have increased the demand for characterization methods capable of probing nanoscale features on ultrafast time scales. As the sample reduces to atomically thin levels, an extremely low-level signal limits the feasibility of many experiments. Here, we present an affordable and easy-to-implement solution to expand the maximum sensitivity of lock-in detection systems used in transient absorption spectroscopy by multiple orders of magnitude. By implementation of a tuned RC circuit to the output of an avalanche photodiode, electric pulse shaping allows for vastly improved lock-in detection. Furthermore, a carefully designed “peak detector” circuit provides additional pulse shaping benefits, resulting in even more lock-in detection signal enhancement. We demonstrate the improvement of lock-in detection with each of these schemes by performing benchmark measurements of a white-light continuum signal and micro-transient absorption spectroscopy on a few-layer transition metal dichalcogenide sample. Our results show the practicality of ultrafast pump–probe spectroscopy for many high-sensitivity experimental schemes.