Fluorescence-quenching-based chemical detection represents one of the most sensitive and convenient methods that have been widely employed in explosives identification. [1][2][3][4][5][6] Aromatic molecules and conjugated polymers (when fabricated as films) are proven effective in sensing explosives vapor via fluorescence quenching. Although porous films of conjugated polymers have typically been utilized, the quenching efficiency of these materials is often limited by the short exciton diffusion because of the poor molecular organization and/or weak intermolecular electronic interactions. 2,4 Consequently, very thin films are needed to achieve desirable amplification of signal transduction, whereas a sufficiently thick film is usually required to produce a measurable fluorescence intensity and to minimize the interference of photobleaching. Because of these limitations, there is a need to develop new sensing materials that enable long-range exciton migration and thus produce sensing systems independent of film thickness and with more flexibility for device fabrication.Herein we report an efficient sensing film fabricated from the alkoxycarbonyl-substituted, carbazole-cornered, arylene-ethynylene tetracycle (ACTC), shown in Scheme 1. The incorporation of carbazole enhances the electron donating power of the molecule and thus increases the efficiency of fluorescence quenching by oxidative explosives. The large-area planar molecular surface of ACTC enables effective long-range π-π stacking between the molecules. 7 Nanofibers in length of micrometers can be easily fabricated via surface casting (see Supporting Information). It has been demonstrated that one-dimensional π-π stacking is highly favorable for exciton migration via cofacial intermolecular electronic coupling. [8][9][10] Thereby, long-range exciton diffusion would be expected within the film cast from ACTC. Moreover, the shapepersistent molecular structure of ACTC,11,12 in combination with the networks formed by interdigitated nanofibers, produces multiscale porosity, making it an ideal sensing material for probing oxidative gaseous molecules. Indeed, efficient fluorescence quenching is observed when the ACTC film is exposed to explosives vapor, leading to potential applications in explosives sensing.This investigation was primarily focused on two explosives compounds, 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), which both exist in commercial explosive products and have been widely exploited for the purpose of evaluating explosive sensing devices. The ACTC film was fabricated by spin-casting a THF solution (0.2-1.0 mM) onto a glass substrate, followed by annealing in vacuum at 60°C for 3 h to remove the enclathrated solvent. The film thus fabricated is quite fluorescent, with a quantum yield of ca. 0.19. Upon exposure to saturated vapor of DNT or TNT, the fluorescence of the ACTC film was dramatically quenched ( Figure 1A). Since the emission wavelength of ACTC is far above the absorption range of the two explosives ( Figures S5-S6, Support...

We have demonstrated a single molecule field effect transistor (FET) which consists of a redox molecule (perylene tetracarboxylic diimide) covalently bonded to a source and drain electrode and an electrochemical gate. By adjusting the gate voltage, the energy levels of empty molecular states are shifted to the Fermi level of the source and drain electrodes. This results in a nearly 3 orders of magnitude increase in the source-drain current, in the fashion of an n-type FET. The large current increase is attributed to an electron transport mediated by the lowest empty molecular energy level when it lines up with the Fermi level.

Well-defined ultrathin nanoribbons have been fabricated from an amphiphilic electron donor-acceptor (D-A) supramolecule comprising perylene tetracarboxylic diimide as the backbone scaffold to enforce the one-dimensional intermolecular assembly via strong pi-stacking. These nanoribbons demonstrated high photoconductivity upon illumination with white light. The high photoconductivity thus obtained is likely due to the optimal molecular design that enables a good kinetic balance between the two competitive processes, the intramolecular charge recombination (between D and A) and the intermolecular charge transport along the nanoribbon. The photoconduction response has also proven to be prompt and reproducible with the light turning on and off. The photogenerated electrons within the nanoribbon can be efficiently trapped by the adsorbed oxygen molecules or other oxidizing species, leading to depletion of the charge carriers (and thus the electrical conductivity) of the nanoribbon, as typically observed for n-type semiconductor materials as applied in chemiresistors. Combination of this sensitive modulation of conductivity with the unique features intrinsic to the nanoribbon morphology (large surface area and continuous nanoporosity when deposited on a substrate to form a fibril film) enables efficient vapor sensing of nitro-based explosives.

Intrinsic graphene is a semimetal or zero bandgap semiconductor, which hinders its applications for nanoelectronics. To develop high-performance nanodevices with graphene, it is necessary to open the bandgap and precisely control the charge carrier type and density. In this perspective, we focus on tailoring the electronic properties of graphene by noncovalent stacking with aromatic molecules through π–π interaction. Different types of molecules (functioning as either an electron donor or acceptor when stacked with graphene) as reported in recent literature are presented regarding surface patterning, bandgap engineering, surface doping, as well as applications in nanodevices, particularly the field-effect transistors (FETs). On the basis of the current progress along this research line, future issues and challenges are also briefly discussed.

A new type of fluorescence sensory material with high sensitivity, selectivity, and photostability has been developed for vapor probing of organic amines. The sensory material is primarily based on well-defined nanofibers fabricated from an n-type organic semiconductor molecule, N-(1-hexylheptyl)perylene-3,4,9,10-tetracarboxyl-3,4-anhydride-9,10-imide. Upon deposition onto a substrate, the entangled nanofibers form a meshlike, highly porous film, which enables expedient diffusion of gaseous analyte molecules within the film matrix, leading to milliseconds response for the vapor sensing.

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BackgroundLysyl oxidase-like 4 (LOXL4) has been found to be dysregulated in several human malignancies, including hepatocellular carcinoma (HCC). However, the role of LOXL4 in HCC progression remains largely unclear. In this study, we investigated the clinical significance and biological involvement of LOXL4 in the progression of HCC.MethodsLOXL4 expression was measured in HCC tissues and cell lines. Overexpression, shRNA-mediated knockdown, recombinant human LOXL4 (rhLOXL4), and deletion mutants were applied to study the function of LOXL4 in HCC. Exosomes derived from HCC cell lines were assessed for the ability to promote cancer progression in standard assays. The effects of LOXL4 on the FAK/Src pathway were examined by western blotting.ResultsLOXL4 was commonly upregulated in HCC tissues and predicted a poor prognosis. Elevated LOXL4 was associated with tumor differentiation, vascular invasion, and tumor-node-metastasis (TNM) stage. Overexpression of LOXL4 promoted, whereas knockdown of LOXL4 inhibited cell migration and invasion of HCC in vitro, and overexpressed LOXL4 promoted intrahepatic and pulmonary metastases of HCC in vivo. Most interestingly, we found that HCC-derived exosomes transferred LOXL4 between HCC cells, and intracellular but not extracellular LOXL4 promoted cell migration by activating the FAK/Src pathway dependent on its amine oxidase activity through a hydrogen peroxide-mediated mechanism. In addition, HCC-derived exosomes transferred LOXL4 to human umbilical vein endothelial cells (HUVECs) though a paracrine mechanism to promote angiogenesis.ConclusionsTaken together, our data demonstrate a novel function of LOXL4 in tumor metastasis mediated by exosomes through regulation of the FAK/Src pathway and angiogenesis in HCC.Electronic supplementary materialThe online version of this article (10.1186/s12943-019-0948-8) contains supplementary material, which is available to authorized users.

Sepsis is an excessive inflammatory condition with a high mortality rate and limited prediction and therapeutic options. In this study, for the first time, to our knowledge, we found that downregulation and/or blockade of T cell Ig and mucin domain protein 3 (Tim-3), a negative immune regulator, correlated with severity of sepsis, suggesting that Tim-3 plays important roles in maintaining the homeostasis of sepsis in both humans and a mouse model. Blockade and/or downregulation of Tim-3 led to increased macrophage activation, which contributed to the systemic inflammatory response in sepsis, whereas Tim-3 overexpression in macrophages significantly suppressed TLR-mediated proinflammatory cytokine production, indicating that Tim-3 is a negative regulator of TLR-mediated immune responses. Cross-talk between the Tim-3 and TLR4 pathways makes TLR4 an important contributor to Tim-3–mediated negative regulation of the innate immune response. Tim-3 signaling inhibited LPS–TLR4–mediated NF-κB activation by increasing PI3K–AKT phosphorylation and A20 activity. This negative regulatory role of Tim-3 reflects a new adaptive compensatory and protective mechanism in sepsis victims, a finding of potential importance for modulating innate responses in these patients.