Infrared spectroscopy, especially for molecular vibrations in the fingerprint region between 600 and 1,500 cm−1, is a powerful characterization method for bulk materials. However, molecular fingerprinting at the nanoscale level still remains a significant challenge, due to weak light–matter interaction between micron-wavelengthed infrared light and nano-sized molecules. Here we demonstrate molecular fingerprinting at the nanoscale level using our specially designed graphene plasmonic structure on CaF2 nanofilm. This structure not only avoids the plasmon–phonon hybridization, but also provides in situ electrically-tunable graphene plasmon covering the entire molecular fingerprint region, which was previously unattainable. In addition, undisturbed and highly confined graphene plasmon offers simultaneous detection of in-plane and out-of-plane vibrational modes with ultrahigh detection sensitivity down to the sub-monolayer level, significantly pushing the current detection limit of far-field mid-infrared spectroscopies. Our results provide a platform, fulfilling the long-awaited expectation of high sensitivity and selectivity far-field fingerprint detection of nano-scale molecules for numerous applications.

Most van der Waals crystals present highly anisotropic optical responses due to their strong in-plane covalent bonding and weak out-of-plane interactions. However, the determination of the polarization-dependent dielectric constants of van der Waals crystals remains a nontrivial task, since the size and dimension of the samples are often below or close to the diffraction limit of the probe light. In this work, we apply an optical nano-imaging technique to determine the anisotropic dielectric constants in representative van der Waals crystals. Through the study of both ordinary and extraordinary waveguide modes in real space, we are able to quantitatively determine the full dielectric tensors of nanometer-thin molybdenum disulfide and hexagonal boron nitride microcrystals, the most-promising van der Waals semiconductor and dielectric. Unlike traditional reflection-based methods, our measurements are reliable below the length scale of the free-space wavelength and reveal a universal route for characterizing low-dimensional crystals with high anisotropies.

A new hybridized plasmon-phonon polariton mode in graphene/h-BN van der Waals heterostructures is presented, featuring the ultrahigh field confinement characteristic of the graphene plasmon and the long lifetime property of the h-BN transverse optical phonon. This enables an ultralong hybrid plasmon lifetime of up to 1.6 ps (with ultrahigh mode confinement up to >l0(2)/7000 and ultrasmall group velocity down to 0.001c, where c is the speed of light in vacuum), superior to any localized plasmon ever demonstrated.

Biobased polymeric materials are gaining increasing attention in biomedical areas. Here, we report a new class of biocompatible polyurethanes prepared from soybean oil-based polyol that was synthesized by ring-opening reaction of epoxidized monoglyceride (EMG) with lactic acid. By adjusting the molar ratio of hydroxyl to isocyanate group and the content of chain extender, soybean oil-based polyurethanes with tensile strength of 9.30-27.1 MPa and elongation at break of 74.1-110.7% were prepared, while usual lipid-based polyurethanes with the same 1,6-diisocyanatohexane as reactant hardly have tensile strength higher than 5 MPa. Mouse fibroblast cells (L-929) showed good adhesion and growth behavior on the polyurethane samples with more hydrophilic surfaces, and the cell viabilities of more than 50% were achieved with commercial tissue culture polystyrene (TCPS) disk as control. The good mechanical property and biocompatibility of the soybean oil-based polyurethanes will make them suitable for wide range of potential biomedical applications.Practical applications: The synthesized soybean oil-based polyurethanes have adjustable tensile strengths from 9.30-27.1 MPa and elongation at break of 74.1-110.7%. Along with their good biocompatibility, the polyurethanes can potentially replace wide range of part of petroleum-based polymeric materials, particularly as biomedical materials.

Microbes play an essential role in the decomposition process but were poorly understood in their succession and behaviour. Previous researches have shown that microbes show predictable behaviour that starts at death and changes during the decomposition process. Research of such behaviour enhances the understanding of decomposition and benefits estimating the postmortem interval (PMI) in forensic investigations, which is critical but faces multiple challenges. In this study, we combined microbial community characterization, microbiome sequencing from different organs (i.e. brain, heart and cecum) and machine learning algorithms [random forest (RF), support vector machine (SVM) and artificial neural network (ANN)] to investigate microbial succession pattern during corpse decomposition and estimate PMI in a mouse corpse system. Microbial communities exhibited significant differences between the death point and advanced decay stages. Enterococcus faecalis, Anaerosalibacter bizertensis, Lactobacillus reuteri, and so forth were identified as the most informative species in the decomposition process. Furthermore, the ANN model combined with the postmortem microbial data set from the cecum, which was the best combination among all candidates, yielded a mean absolute error of 1.5 AE 0.8 h within 24-h decomposition and 14.5 AE 4.4 h within 15-day decomposition. This integrated model can serve as a reliable and accurate technology in PMI estimation.

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All‐optical modulators are attracting significant attention due to their intrinsic perspective on high‐speed, low‐loss, and broadband performance, which are promising to replace their electrical counterparts for future information communication technology. However, high‐power consumption and large footprint remain obstacles for the prevailing nonlinear optical methods due to the weak photon–photon interaction. Here, efficient all‐optical mid‐infrared plasmonic waveguide and free‐space modulators in atomically thin graphene‐MoS2 heterostructures based on the ultrafast and efficient doping of graphene with the photogenerated carrier in the monolayer MoS2 are reported. Plasmonic modulation of 44 cm−1 is demonstrated by an LED with light intensity down to 0.15 mW cm−2, which is four orders of magnitude smaller than the prevailing graphene nonlinear all‐optical modulators (≈103 mW cm−2). The ultrafast carrier transfer and recombination time of photogenerated carriers in the heterostructure may achieve ultrafast modulation of the graphene plasmon. The demonstration of the efficient all‐optical mid‐infrared plasmonic modulators, with chip‐scale integrability and deep‐sub wavelength light field confinement derived from the van der Waals heterostructures, may be an important step toward on‐chip all‐optical devices.

Monodispersed inorganic oxide nanoparticles are one kind of the most commonly used templates for efficient and controllable preparation of conducting polymer nanostructures. In this article, we report the fabrication and characterization of PPycoated cotton fabrics through in situ chemical polymerization by using CuO nanoparticles as template. The electrical conductivity of the coated samples increases dramatically to 10.0 S cm -1 with the introduction of CuO. The electrochemical properties of the obtained fabrics are examined by cyclic voltammetry and charge/discharge analysis. The increase of scan rate in the range of 5-50 mV s -1 has a small effect on the specific capacitance for the fabric electrode, pointing out the improved ion transportation in this electrode. The charge/discharge test further reveals that the fabric device shows high specific capacitance (225 F g -1 at a current density of 0.6 mA cm -2 ) and good cycling performance (about 92 % capacitance retention after 200 cycles) in aqueous electrolyte. These PPy-coated fabrics have potential to be used as electrode materials for wearable supercapacitors.