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Plasmonic nanopores combined with Raman spectroscopy are emerging as platforms for single-molecule detection and sequencing in label-free mode. Recently, the ability of identifying single DNA bases or amino acids has been demonstrated for molecules adsorbed on plasmonic particles and then delivered into the plasmonic pores. Here, we report on bowl-shaped plasmonic gold nanopores capable of direct Raman detection of single λ-DNA molecules in a flow-through scheme. The bowl shape enables the incident laser to be focused into the nanopore to generate a single intense hot spot with no cut off in pore size. Therefore, we achieved ultrasmall focusing of NIR light in a spot of 3 nm. This enabled us to detect 7 consecutive bases along the DNA chain in flow-through conditions. Furthermore, we found a novel electrofluidic mechanism to manipulate the molecular trajectory within the pore volume so that the molecule is pushed toward the hot spot, thus improving the detection efficiency.

Elucidating the autoxidation of volatile organic compounds (VOCs) is crucial to understanding the formation mechanism of secondary organic aerosols, but it has been proven to be challenging due to the complexity of reactions under atmospheric conditions. Here, we report a comprehensive theoretical study of atmospheric autoxidation in VOCs exemplified by the atmospherically important methacrolein (MACR), a major oxidation product of isoprene. The results indicate that the Cl-adducts and H-abstraction products of MACR readily react with O2and undergo subsequent isomerizations via H-shift and cyclization, forming a large variety of lowly and highly oxygenated organic molecules. In particular, the first- and third-generation oxidation products derived from the Cl-adducts and the methyl-H-abstraction complexes are dominated in the atmospheric autoxidation, for which the fractional yields are remarkably affected by the NO concentration. The present findings have important implications for a systematical understanding of the oxidation processes of isoprene-derived compounds in the atmospheric environments.

Deoxyinosine (dI) is a highly mutagenic lesion that preferentially pairs with deoxycytidine during replication, which may induce A to G transition and ultimately contribute to carcinogenesis. Therefore, finding the site of dI modification in DNA is of great value for both basic research and clinical applications. Herein, we developed a novel method to sequence the dI modification site in DNA, which utilizes endonuclease V (EndoV)-dependent deamination repair to specifically label the modification site with biotin-14-dATP that allows the affinity enrichment of dI-bearing DNA for sequencing. We have achieved efficient determination of the location of the modified nucleotide in dI-bearing plasmid DNA with the assistance of EndoV-dependent deamination repair. We have also successfully applied this approach to locate the dI modification sites in the mitochondrial DNA of human cells. Our method should be generally applicable for genome-wide sequencing analysis of dI modifications in living organisms.

Durable and multilevel information encryption technology has been of great importance in recent decades. Here, an inkjet printer-adaptable invisible ink was prepared with lanthanide nanoparticles, and optical decoding of information could only be achieved when specific ligand dipicolinic acid was utilized in the presence of UV illumination. In addition, the proposed protocols displayed long shelf life (>one year) and excellent durability even at harsh conditions such as in the presence of strong acids (1 M HCl) and alkalis (1 M NaOH). Meanwhile, such invisible inks could be further employed on a soft matrix via screen-printing, holding great potential for practical applications.

Engineered electromagnetic fields in plasmonic nanopores enable enhanced optical detection for single-molecule sensing and sequencing. Here, a plasmonic nanopore prepared in a thick nanoporous film is used to investigate, by means of surface-enhanced Raman spectroscopy, the interaction between the metallic surface of the pore and a long-chain double-strand DNA molecule free to diffuse through the pore. We discuss how the matrix of the porous material can interact with the molecule thanks to: (i) transient aspecific interactions between the porous surface and DNA; (ii) diffusion; and (iii) thermal and optical forces exerted by the localized field in a metallic nanostructure on the DNA molecule. An interaction time up to tens of milliseconds enables us to collect high signal-to-noise Raman signatures, allowing an easy label-free reading of information from the DNA molecule. Moreover, to increase the rate of detection, we tested a polymeric porous hydrogel placed beneath the solid-state membrane. The hydrogel enables a slowdown of the molecule diffusion time, thus increasing the number of detected interaction events by a factor 20. The analysis of the observed Raman peaks and their relative intensities, combined with theoretical simulations, allows us to get further information on the process of translocation and the folding state and orientation of the translocating molecule. Our results demonstrate temporary adsorption of the DNA molecule on the porous material during the translocation due to the diffusion force. Finally, we provide a qualitative evaluation of the nucleotides’ contents in the different groups of collected signal. The proposed approach can find interesting applications not only in DNA sensing and sequencing but also on generic nanopore spectroscopy.

Unraveling bacterial identity through Raman scattering techniques has been persistently challenging due to homogeneously amplified Raman signals across a wide variety of bacterial molecules, predominantly protein- or nucleic acid-mediated. In this study, we present an approach involving the use of silver nanoparticles to completely and uniformly “mask” adsorption on the surface of bacterial molecules through sodium borohydride and sodium chloride. This approach enables the acquisition of enhanced surface-enhanced Raman scattering (SERS) signals from all components on the bacterial surface, facilitating rapid, specific, and label-free bacterial identification. For the first time, we have characterized the identity of a bacterium, including its DNA, metabolites, and cell walls, enabling the accurate differentiation of various bacterial strains, even within the same species. In addition, we embarked on an exploration of the origin and variability patterns of the main characteristic peaks of Gram-positive and Gram-negative bacteria. Significantly, the SERS peak ratio was found to determine the inflection point of accelerated bacterial death upon treatment with antimicrobials. We further applied this platform to identify 15 unique clinical antibiotic-resistant bacterial strains, including five Escherichia colistrains in human urine, a first for Raman technology. This work has profound implications for prompt and accurate identification of bacteria, particularly antibiotic-resistant strains, thereby significantly enhancing clinical diagnostics and antimicrobial treatment strategies.

We introduce a novel concept of hybrid metal-dielectric meta-antenna supporting type II hyperbolic dispersion, which enables full control of absorption and scattering of light in the visible/near-infrared spectral range. This ability lies in the different nature of the localized hyperbolic Bloch-like modes excited within the meta-antenna. The experimental evidence is corroborated by a comprehensive theoretical study. In particular, we demonstrate that two main modes, one radiative and one non-radiative, can be excited by direct coupling with the free-space radiation. We show that the scattering is the dominating electromagnetic decay channel, when an electric dipolar mode is induced in the system, whereas a strong absorption process occurs when a magnetic dipole is excited. Also, by varying the geometry of the system, the relative ratio of scattering and absorption, as well as their relative enhancement and/or quenching, can be tuned at will over a broad spectral range, thus enabling full control of the two channels. Importantly, both radiative and nonradiative modes supported by our architecture can be excited directly with far-field radiation. This is observed to occur even when the radiative channels (scattering) are almost totally suppressed, thereby making the proposed architecture suitable for practical applications. Finally, the hyperbolic meta-antennas possess both angular and polarization independent structural integrity, unlocking promising applications as hybrid meta-surfaces or as solvable nanostructures.

Delivery of molecules into intracellular compartments is one of the fundamental requirements in molecular biology. However, the possibility of delivering a precise number of nano-objects with single-particle resolution is still an open challenge. Here we present an electrophoretic platform based on 3D hollow nanoelectrodes to enable delivery of single nanoparticles into single selected cells and monitoring of the single-particle delivery by surface-enhanced Raman scattering (SERS). The gold-coated hollow nanoelectrode capable of confinement and enhancement of electromagnetic fields upon laser illumination can distinguish the SERS signals of a single nanoparticle flowing through the nanoelectrode. Tight wrapping of cell membranes around the nanoelectrodes allows effective membrane electroporation such that single gold nanorods are delivered on demand into a living cell by electrophoresis. The capability of the 3D hollow nanoelectrodes to porate cells and reveal single emitters from the background in continuous flow is promising for the analysis of both intracellular delivery and sampling.

Using electroabsorption spectroscopy, we explore the polarizability of Frenkel excitons in both pristine donor and D/A blend films. We observe for the first time that the polarizability of excitonic states in pristine donors can be dramatically increased by adding an n-type acceptor. By investigating the dielectric effect in different organic semiconductor systems, we find that the polarizability of Frenkel excitons has direct correlation with the measured dielectric constant of the bulk heterojunction thin films. Our results disclose the difference in the nature of Frenkel excitons in pristine donor and D/A blend systems, revealing an important role of excitonic states in charge separation process of organic photovoltaic devices.

ABSTRACTBackground Direct observation of clinical skills is a cornerstone of competency-based education and training. Ensuring direct observation in a consistent fashion has been a significant challenge for residency programs.Objective The purpose of this study was to evaluate the effects of a novel evaluation system, designed to achieve ongoing direct observation of residents, examine changes in resident observation practices, and understand faculty attitudes toward direct observation and the evaluation system.Methods Internal medicine residents on an ambulatory block rotation participated in a new evaluation system, which replaced a single end-of-rotation summative evaluation with 9 formative evaluations based on direct observation. Faculty received training in direct observation and use of the forms, and residents were given responsibility to collect 9 observations per rotation. Faculty members contacted residents at the beginning and middle of the rotation to ensure completion of the observations. Residents and faculty also completed postrotation surveys to gauge the impact of the new system.Results A total of 507 patient encounters were directly observed, and 52 of 57 (91) residents completed all 9 observations. Residents reported considerably more direct observation than prior to the intervention, and most reported changes to their clinical skills based on faculty feedback. Faculty reported improvements in their attitudes, increased their use of direct observation, and preferred the new system to the old one.Conclusions A novel evaluation system replacing summative evaluations with multiple formative evaluations based on direct observation was successful in achieving high rates of observations, and improving faculty attitudes toward direct observation.

Purpose: This exploratory research aims to investigate the barriers to career advancement for women accountants in China. Design/methodology/approach: Semi-structured interviews were conducted with eight accountants working for business companies and occupying different-level positions. Findings: Women accountants in China encounter barriers throughout their career paths. The main barrier is a negative perception of women’s work performance after having a child. Although the modern communist state claims that women have a role equal to that of men in their work contributions, centuries-old Confucian attitudes constrain women in their choices of balance between work and home life. Originality/value: The findings of this research call for enforcement of employment laws in China to give women equal opportunities in both recruitment and promotion. This research contributes to both Western and Chinese existing literature, confirming some prior findings that are contrary to modern China’s rhetoric that “Women hold up half the sky”. It also adds the perspective of accountants working in business companies rather than public practice accounting firms.