The tip shape dependence of the STM-induced luminescence

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Influence of the Tip Shape on Scanning Tunneling Luminescence Spectra: Implications for Nanomaterial Characterization

Scanning tunneling luminescence (STL) provides a unique opportunity to determine the optical properties of nanostructures beyond the diffraction limit. However, the relationship between the STL spectra and nanoscale tip shapes remains poorly understood because of the uncertainty regarding the nanoscale tip geometry. Here, we provide direct experimental evidence supporting a relationship between the tip shapes and resulting STL spectra. We find that asymmetric nanoscale tips generated dissimilar STL spectra in different directions by simultaneously collecting STL spectra in two opposing directions. Our experiment provides an efficient way to tune the STL spectra, which can be used to characterize the optical properties of nanomaterials.11Nsciescopu

Tunable Plasmonic Quantum Light Source with Silver Nanoclusters on a Silver Surface

Scanning tunneling luminescence (STL) can be used to investigate the optical properties of nanostructures with high spatial resolution beyond the diffraction limit of light. To get appropriate STL spectra, one needs to modify the tip repeatedly. However, such irreversible tip modification often leads to very unstable tips. Here, by using a scanning tunneling microscope (STM) tip, we demonstrate that STL spectra are tunable via silver nanocluster arrays fabricated directly on a silver surface. The silver nanoclusters are created by transferring silver atoms from the silver tip to the silver surface under STM. We found that the STL spectra were enhanced (suppressed) at higher (lower) energy on the clusters and that they showed opposite behaviors between the nanoclusters. Without relying on the irreversible tip shape modification, our findings indicate that we can tune the STL spectra simply by moving the STM tip over the nanoclusters. Our method can be used to provide a tunable light source for systematic nano-optical experiments and for nanoscale optical devices.11Nsciescopuskc

Unusual Diffusion Behavior of Copper-Hexadecafluoro-Phthalocyanine Molecules on Au(111)

© 2020, The Korean Physical Society. The unusual bias-voltage dependence of copper-hexadecafluoro-phthalocyanine (F16CuPc) molecules on Au(111) was investigated by using scanning tunneling microscopy/spectroscopy (STM/STS) at low temperatures. Depending on the bias polarity, the molecules seem to cover the whole surface of Au(111) at positive bias voltages while they are apparently invisible in STM images at negative bias voltages. Here, we experimentally demonstrate that the molecular diffusivity on Au(111) varies according to the applied electric field induced between the STM tip and the Au(111) surface rather than the intrinsic molecule-substrate interaction. Such results are corroborated by STS measurements indicating that attraction/repulsion of a molecule indeed occurs under an STM tip at positive/negative bias voltages during sweeps of the bias voltage. In addition, we found that the diffusive molecules are immobilized at a temperature of 8 K at both positive and negative bias voltages due to a lack of thermal energy for diffusion11sciekc

Detecting the Tip Shape Dependence of the Plasmonic Photon Emission under STM

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Spherical nucleic acids-based nanoplatforms for tumor precision medicine and immunotherapy

Precise diagnosis and treatment of tumors currently still face considerable challenges due to the development of highly degreed heterogeneity in the dynamic evolution of tumors. With the rapid development of genomics, personalized diagnosis and treatment using specific genes may be a robust strategy to break through the bottleneck of traditional tumor treatment. Nevertheless, efficient in vivo gene delivery has been frequently hampered by the inherent defects of vectors and various biological barriers. Encouragingly, spherical nucleic acids (SNAs) with good modularity and programmability are excellent candidates capable of addressing traditional gene transfer-associated issues, which enables SNAs a precision nanoplatform with great potential for diverse biomedical applications. In this regard, there have been detailed reviews of SNA in drug delivery, gene regulation, and dermatology treatment. Still, to the best of our knowledge, there is no published systematic review summarizing the use of SNAs in oncology precision medicine and immunotherapy, which are considered new guidelines for oncology treatment. To this end, we summarized the notable advances in SNAs-based precision therapy and immunotherapy for tumors following a classification standard of different types of precise spatiotemporal control on active species by SNAs. Specifically, we focus on the structural diversity and programmability of SNAs. Finally, the challenges and possible solutions were discussed in the concluding remarks. This review will promote the rational design and development of SNAs for tumor-precise medicine and immunotherapy

Geometric Dependence of Tip Shape on Scanning Tunneling Luminescence Spectra.

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Casting red light for bad oil by dual turning-on mechanisms of fluorescence and its application in the portable platform

© 2022 Elsevier B.V.Cooking oil undergoes complicated reactions and generates harmful chemicals during the cooking process. Unfortunately, part of the bad cooking oil was illegally recycled and sold back to consumers. The conventional detection methods usually require heavy equipment and professional skills, which are not easily accessible to the public. Herein, we describe a robust turn-on fluorescent molecular probe, BOS (Bad Oil Sensor), for the straightforward and highly sensitive detection of bad cooking oil. BOS detects bad oil through the inevitable intrinsic change of viscosity and pH during cooking. Therefore, BOS enables the monitoring of cooking extent for any bad oil regardless of the origins, including adulterated oil. With the dual turn-on mechanisms and high sensitivity of BOS, a portable platform named Bad Oil Sensing System (BOSS) was constructed for the quick and simple in-field detection of bad oil. We believe that BOS and its portable platform will become a widely applicable tool for oil quality monitoring for the public and in the field of food chemistry.11Nsciescopu