In vivo fluorescence imaging in the second near-infrared window (1.0-1.7 mm) can afford deep tissue penetration and high spatial resolution, owing to the reduced scattering of long-wavelength photons. Here we synthesize a series of low-bandgap donor/acceptor copolymers with tunable emission wavelengths of 1,050-1,350 nm in this window. Noncovalent functionalization with phospholipid-polyethylene glycol results in water-soluble and biocompatible polymeric nanoparticles, allowing for live cell molecular imaging at 41,000 nm with polymer fluorophores for the first time. Importantly, the high quantum yield of the polymer allows for in vivo, deep-tissue and ultrafast imaging of mouse arterial blood flow with an unprecedented frame rate of 425 frames per second. The high time-resolution results in spatially and time resolved imaging of the blood flow pattern in cardiogram waveform over a single cardiac cycle (B200 ms) of a mouse, which has not been observed with fluorescence imaging in this window before.

We have developed a class of blackbody materials, i. e., hyperbranched Au plasmonic blackbodies (AuPBs), of compact sizes (<50 nm). The AuPBs were prepared in a seedless and surfactant-free approach based on the use of mussel-inspired dopamine. Strong intraparticle plasmonic coupling among branches in close proximity leads to intense and uniform broadband absorption across 400-1350 nm. The blackbody absorption imparts the compact AuPB with a superior photothermal efficiency of >80% and closely matched photothermal activity in the first near-infrared (NIR-I) and the second near-infrared (NIR-II) spectral windows, making it a rare broadband theranostic probe for integrated photoacoustic imaging and photothermal therapy (PTT). Our comparative study, using the same probe, has demonstrated that the improved PTT outcome of NIR-II over NIR-I primarily results from its higher maximum permission exposure (MPE) rather than the deeper tissue penetration favored by longer wavelengths. The compact plasmonic broadband nanoabsorbers with tailored surface properties hold potential for a wide spectrum of light-mediated applications.

Upconversion, the conversion of photons from lower to higher energies, is a process that promises applications ranging from high-efficiency photovoltaic and photocatalytic cells to background-free bioimaging and therapeutic probes. Existing upconverting materials, however, remain too inefficient for viable implementation. In this Perspective, we describe the significant improvements in upconversion efficiency that can be achieved using plasmon resonances. As collective oscillations of free electrons, plasmon resonances can be used to enhance both the incident electromagnetic field intensity and the radiative emission rates. To date, this approach has shown upconversion enhancements up to 450×. We discuss both theoretical underpinnings and experimental demonstrations of plasmon-enhanced upconversion, examining the roles of upconverter quantum yield, plasmonic geometry, and plasmon spectral overlap. We also discuss nonoptical consequences of including metal nanostructures near upconverting emitters. The rapidly expanding field of plasmon-enhanced upconversion provides novel fundamental insight into nanoscale light-matter interactions while improving prospects for technological relevance.

Phenolics are readily accessible molecules with versatile reactivity and good biocompatibility—they have catalyzed research into phenolic-enabled nanotechnology thus providing a powerful toolkit for on-demand particle engineering in biomedicine.

NaYF4:Yb(3+),Er(3+) nanoparticle upconverters are hindered by low quantum efficiencies arising in large part from the parity-forbidden nature of their optical transitions and the nonoptimal spatial separations between lanthanide ions. Here, we use pressure-induced lattice distortion to systematically modify both parameters. Although hexagonal-phase nanoparticles exhibit a monotonic decrease in upconversion emission, cubic-phase particles experience a nearly 2-fold increase in efficiency. In-situ X-ray diffraction indicates that these emission changes require only a 1% reduction in lattice constant. Our work highlights the intricate relationship between upconversion efficiency and lattice geometry and provides a promising approach to modifying the quantum efficiency of any lanthanide upconverter.

Photothermal therapy (PTT), a local heating photothermal effect induced by a near-infrared (NIR) laser irradiation, is a promising method for ablating tumors with poorly vascularized microenvironment. [1] The local heating with a high temporal and spatial control can be realized by using an NIR light Transition metal dichalcogenide (TMD) nanomaterials, specially MoS 2 , are proven to be appealing nanoagents for photothermal cancer therapies. However, the impact of the crystal phase of TMDs on their performance in photoacoustic imaging (PAI) and photothermal therapy (PTT) remains unclear. Herein, the preparation of ultrasmall single-layer MoS 2 nanodots with different phases (1T and 2H phase) is reported to explore their phasedependent performances as nanoagents for PAI guided PTT in the second near-infrared (NIR-II) window. Significantly, the 1T-MoS 2 nanodots give a much higher extinction coefficient (25.6 L g −1 cm −1) at 1064 nm and subsequent photothermal power conversion efficiency (PCE: 43.3%) than that of the 2H-MoS 2 nanodots (extinction coefficient: 5.3 L g −1 cm −1 , PCE: 21.3%). Moreover, the 1T-MoS 2 nanodots also give strong PAI signals as compared to negligible signals of 2H-MoS 2 nanodots in the NIR-II window. After modification with polyvinylpyrrolidone, the 1T-MoS 2 nanodots can be used as a highly efficient agent for PAI guided PTT to effectively ablate cancer cells in vitro and tumors in vivo under 1064 nm laser irradiation. This work proves that the crystal phase plays a key role in determining the performance of nanoagents based on TMD nanomaterials for PAI guided PTT.

Sustainable developments of nanotechnology necessitate the exploration of structure-activity relationships (SARs) at nano-bio interfaces. While ferroptosis may contribute in the developments of some severe diseases (e.g., Parkinson’s disease, stroke and tumors), the cellular pathways and nano-SARs are rarely explored in diseases elicited by nano-sized ferroptosis inducers. Here we find that WS 2 and MoS 2 nanosheets induce an iron-dependent cell death, ferroptosis in epithelial (BEAS-2B) and macrophage (THP-1) cells, evidenced by the suppression of glutathione peroxidase 4 (GPX4), oxygen radical generation and lipid peroxidation. Notably, nano-SAR analysis of 20 transition metal dichalcogenides (TMDs) disclosures the decisive role of surface vacancy in ferroptosis. We therefore develop methanol and sulfide passivation as safe design approaches for TMD nanosheets. These findings are validated in animal lungs by oropharyngeal aspiration of TMD nanosheets. Overall, our study highlights the key cellular events as well as nano-SARs in TMD-induced ferroptosis, which may facilitate the safe design of nanoproducts.

The production of bulk chemicals and fuels from renewable bio-based feedstocks is of significant importance for the sustainability of human society. Adipic acid, as one of the most-demanded drop-in chemicals from a bioresource, is used primarily for the large-volume production of nylon-6,6 polyamide. It is highly desirable to develop sustainable and environmentally friendly processes for the production of adipic acid from renewable feedstocks. However, currently there is no suitable bio-adipic acid synthesis process. Demonstrated herein is the highly efficient synthetic protocol for the conversion of mucic acid into adipic acid through the oxorhenium-complex-catalyzed deoxydehydration (DODH) reaction and subsequent Pt/C-catalyzed transfer hydrogenation. Quantitative yields (99 %) were achieved for the conversion of mucic acid into muconic acid and adipic acid either in separate sequences or in a one-step process.