Black phosphorus quantum dots (BPQDs) were synthesized using a liquid exfoliation method that combined probe sonication and bath sonication. With a lateral size of approximately 2.6 nm and a thickness of about 1.5 nm, the ultrasmall BPQDs exhibited an excellent NIR photothermal performance with a large extinction coefficient of 14.8 L g(-1) cm(-1) at 808 nm, a photothermal conversion efficiency of 28.4%, as well as good photostability. After PEG conjugation, the BPQDs showed enhanced stability in physiological medium, and there was no observable toxicity to different types of cells. NIR photoexcitation of the BPQDs in the presence of C6 and MCF7 cancer cells led to significant cell death, suggesting that the nanoparticles have large potential as photothermal agents.

Although phosphorene has attracted much attention in electronics and optoelectronics as a new type of two‐dimensional material, in‐depth investigations and applications have been limited by the current synthesis techniques. Herein, a basic N‐methyl‐2‐pyrrolidone (NMP) liquid exfoliation method is described to produce phosphorene with excellent water stability, controllable size and layer number, as well as in high yield. Phosphorene samples composed of one to four layers exhibit layer‐dependent Raman scattering characteristics thus providing a fast and efficient means for the in situ determination of the thickness (layer number) of phosphorene. The linear and nonlinear ultrafast absorption behavior of the as‐exfoliated phosphorene is investigated systematically by UV–vis–NIR absorption and Z‐scan measurements. By taking advantage of their unique nonlinear absorption, ultrashort pulse generation applicable to optical saturable absorbers is demonstrated. In addition to a unique fabrication technique, our work also reveals the large potential of phosphorene in ultrafast photonics.

Photothermal therapy (PTT) offers many advantages such as high efficiency and minimal invasiveness, but clinical adoption of PTT nanoagents have been stifled by unresolved concerns such as the biodegradability as well as long-term toxicity. Herein, poly (lactic-co-glycolic acid) (PLGA) loaded with black phosphorus quantum dots (BPQDs) is processed by an emulsion method to produce biodegradable BPQDs/PLGA nanospheres. The hydrophobic PLGA not only isolates the interior BPQDs from oxygen and water to enhance the photothermal stability, but also control the degradation rate of the BPQDs. The in vitro and in vivo experiments demonstrate that the BPQDs/PLGA nanospheres have inappreciable toxicity and good biocompatibility, and possess excellent PTT efficiency and tumour targeting ability as evidenced by highly efficient tumour ablation under near infrared (NIR) laser illumination. These BP-based nanospheres combine biodegradability and biocompatibility with high PTT efficiency, thus promising high clinical potential.

A titanium sulfonate ligand is synthesized for surface coordination of black phosphorus (BP). In contrast to serious degradation observed from the bare BP, the BP after surface coordination exhibits excellent stability during dispersion in water and exposure to air for a long period of time, thereby significantly extending the lifetime and spurring broader application of BP.

Photothermal therapy (PTT) is a fledgling therapeutic strategy for cancer treatment with minimal invasiveness but clinical adoption has been stifled by concerns such as insufficient biodegradability of the PTT agents and lack of an efficient delivery system. Here, black phosphorus (BP) nanosheets are incorporated with a thermosensitive hydrogel [poly(d,l‐lactide)‐poly(ethylene glycol)‐poly(d,l‐lactide) (PDLLA‐PEG‐PDLLA: PLEL)] to produce a new PTT system for postoperative treatment of cancer. The BP@PLEL hydrogel exhibits excellent near infrared (NIR) photothermal performance and a rapid NIR‐induced sol–gel transition as well as good biodegradability and biocompatibility in vitro and in vivo. Based on these merits, an in vivo PTT postoperative treatment strategy is established. Under NIR irradiation, the sprayed BP@PLEL hydrogel enables rapid gelation forming a gelled membrane on wounds and offers high PTT efficacy to eliminate residual tumor tissues after tumor removal surgery. Furthermore, the good photothermal antibacterial performance prevents infection and this efficient and biodegradable PTT system is very promising in postoperative treatment of cancer.

At itanium sulfonate ligand is synthesized for surface coordination of black phosphorus (BP). In contrast to serious degradation observed from the bare BP,the BP after surface coordination exhibits excellent stability during dispersion in water and exposure to air for al ong period of time, therebys ignificantly extending the lifetime and spurring broader application of BP.Atomically thin black phosphorus (BP), an ew member of two-dimensional (2D) materials,h as attracted increasing interest because of its unique electronic and optical properties and promising applications. [1][2][3][4][5][6][7][8][9][10][11][12][13] BP crystals have strong inplane bonds and the weak van der Waals interlayer interaction enables exfoliation into few-layer BP sheets or phosphorene (single-layer BP). [14][15][16][17][18] As am etal-free layered semiconductor,B Ph as thickness-dependent band gaps varying from 0.3 eV for bulk to 2.0 eV for phosphorene. [3] Moreover,B Pw ith high mobility and as izeable band gap is at the electronic intersection of graphene (a zero-gap highmobility 2D material) and semiconducting transition metal dichalcogenides (large-gap low-mobility 2D materials). [2,[19][20][21] These fascinating properties suggest that BP is not only promising in nanoscale electronic devices, [22][23][24][25][26] but also suitable for near-a nd mid-infrared region optoelectronic applications. [27][28][29][30][31] Moreover,BPnanosheets possess excellent photochemical and photothermal properties with potential catalytic and biomedical applications. [11,32] In spite of these promising properties,afundamental obstacle hindering the application of BP is its lack of air-and water-stability. [3] It has been demonstrated that BP is very reactive to oxygen and water under ambient conditions, resulting in compositional and physical changes and consequently considerable degradation in the electronic and optical properties. [10,26,[33][34][35][36] Long-term exposure of BP to humid air or water can even completely etch the materials away.[37] This poses as evere limitation to the adoption of BP in flexible electronics and photoelectronics,a nd its instability in water further limits potential electrochemical and biomedical applications.T herefore,m uch effort has been made to understand the degradation mechanism and to improve the stability of BP. [10,22,[38][39][40][41][42][43] Optical microscopy and atomic force microscopy (AFM) have revealed droplet-like structures on the surface of BP upon exposure to air. [10,37,38] Consequently, capping layers have been developed to encapsulate BP sheets and enhance the air-stability of BP,but oxygen and water may enter through the interfaces causing eventual breakdown. [38] Ther ole of oxygen and water in BP degradation has been studied recently, [42] and it has been shown that degradation of BP under ambient conditions is initiated by contact with oxygen but water does not play aprimary role in the reaction. However,water is capable of removing P x O y from the surface and exposing P 0 to con...

Blackp hosphorus quantum dots (BPQDs) were synthesized using al iquid exfoliation method that combined probe sonication and bath sonication. With al ateral sizeo f approximately 2.6 nm and at hickness of about 1.5 nm, the ultrasmall BPQDs exhibited an excellent NIR photothermal performance with al arge extinction coefficient of 14.8 Lg À1 cm À1 at 808 nm, aphotothermal conversion efficiency of 28.4 %, as well as good photostability.After PEG conjugation, the BPQDs showed enhanced stability in physiological medium, and there was no observable toxicity to different types of cells.N IR photoexcitation of the BPQDs in the presence of C6 and MCF7 cancer cells led to significant cell death, suggesting that the nanoparticles have large potential as photothermal agents.Owing to the superior tissue-penetration ability of nearinfrared (NIR) light, [1] NIR photothermal agents have attracted considerable attention in cancer photothermal therapy (PTT), [2] drug/gene delivery, [3] and tissue engineering. [4] Thei deal photothermal agent should not only have ac onsiderable extinction coefficient and photothermal conversion efficacy in the NIR region, but also satisfy the strict safety requirements of clinical use. [5] Theb iocompatibility of chemical components is the first consideration to ensure safety and proper surface functionalization by means of,f or example,b iocompatible polymers such as PEG,w hich can improve the biocompatibility and facilitate tumor targeting. [6] Thep article size influences both the toxicity and clearance characteristics. [7] In clinical applications,t he therapy agents should be completely cleared from the human body within ar easonable period. Ty pically,e fficient renal and liver clearance requires the agents to be smaller than 10 nm. [7c,d] Va rious nanoparticles with good NIR optical properties have hitherto been developed, and they exhibit efficient photothermal performance in vitro and in vivo. [2,[8][9][10][11][12][13][14][15][16][17][18][19][20][21] However,very few nanoparticles meet the safety requirements,a nd hence, the development of new biocompatible photothermal agents is of scientific and clinical interest.Herein, we describe the synthesis and photothermal properties of ultrasmall black phosphorus quantum dots (BPQDs), which display an excellent NIR photothermal performance and biocompatibility.P hosphorus is av ital element in the human body,a mounting to approximately 660 gi na na dult human and accounting for 1% of the body weight. As one of the three allotropes of phosphorus,b lack phosphorus (BP), ac onceptually new two-dimensional (2D) layered material, has received much interest owing to its unique layered structure and al ayer-dependent bandgap of 0.3 to 2.0 eV. [22] Mechanical and liquid exfoliation methods have been adopted to prepare BP nanosheets with different numbers of layers and sizes, [23] and the products have fascinating applications in electronics and photoelectric devices. [24] However,t heir application in biomedicine is still in its infancy owing to the ...

Poly(vinylpyrrolidone)-encapsulated Bi2 Se3 nanosheets with a thickness of 1.7 nm and diameter of 31.4 nm are prepared by a solution method. Possessing an extinction coefficient of 11.5 L g(-1) cm(-1) at 808 nm, the ultrathin Bi2 Se3 nanosheets boast a high photothermal conversion efficiency of 34.6% and excellent photoacoustic performance. After systemic administration, the Bi2 Se3 nanosheets with the proper size and surface properties accumulate passively in tumors enabling efficient photoacoustic imaging of the entire tumors to facilitate photothermal cancer therapy. In vivo biodistribution studies reveal that they are expelled from the body efficiently after 30 d. The ultrathin Bi2 Se3 nanosheets have large clinical potential as metabolizable near-infrared-triggered theranostic agents.