Publications by authors named "Xingyun Peng"

12 Publications

  • Page 1 of 1

Molecular rotor as a structural probe of glucan polymers: Amylopectin, phytoglycogen, and their β-limit dextrins as models.

Carbohydr Polym 2020 Dec 6;250:116859. Epub 2020 Aug 6.

Department of Food Science, Purdue University, West Lafayette, IN, 47907, United States; Whistler Center for Carbohydrate Research, West Lafayette, IN, 47907, United States. Electronic address:

Fluorescence emissions of molecular rotors (MRs) are affected by local restrictions to molecular motion, and therefore it was considered that MRs can be used as structural probes of biopolymers. In this study, 9-(2-carboxy-2-cyanovinyl)-julolidine (CCVJ), a hydrophilic MR, was used to differentiate branched α-D-glucans, including amylopectin, phytoglycogen, and their β-limit dextrins. CCVJ emissions of glucan dispersions were correlated with dispersion viscosities and glucan branch structures. In diluted glucan dispersions, CCVJ emission showed essentially linear correlation with glucan content. In concentrated glucan dispersions, CCVJ emission correlated with viscosity in a double-logarithmic linear pattern, with phytoglycogen showing much greater sensitivities than amylopectin. In the plots of CCVJ emission vs. molar amount of branch, phytoglycogen materials showed greater slopes than their amylopectin counterparts, suggesting evident effects of branch structure on the restrictions to CCVJ molecules. Overall, CCVJ has demonstrated its fluorescent sensitivity with glucans, showing strong potentials as a structural probe of biopolymers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.carbpol.2020.116859DOI Listing
December 2020

Anisotropic Excitation Polarization Response from a Single White Light-Emitting β-NaYF :Yb ,Pr Microcrystal.

Small 2019 Oct 6;15(43):e1904298. Epub 2019 Sep 6.

College of Optical Science and Engineering, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, 310027, China.

Precise knowledge about optical and structural performance of individual rare earth (RE)-doped particles is extremely important for the optimization of luminescent particles and for fully exploiting their capability as multifunctional probes for interdisciplinary applications. In this work, optical and structural anisotropy of individual particles through RE-doped single fluoride microcrystals with controllable morphology is reported. Unique luminescent phenomena, for example, white light-emission from Pr at single particle level and different photoluminescent spectra variation dependence on excitation polarization orientation at different excitation direction are observed upon excitation with a 980 nm linearly polarized laser. Based on the analysis of local site symmetry and electron cloud distribution of REs in hexagonal structure by density functional theory calculations, an exciting mechanism of excitation polarization response anisotropy is given for the first time, providing a guidance for emission polarization simultaneously. The structural anisotropy is presented in Raman spectra with obvious differing Raman curves, revealing the reason why there are differences between powder groups. Taking advantage of anisotropic crystals, potential applications in microscopic multi-information transportation are suggested for the optical and structural performance anisotropy from RE-doped fluoride single nano/microcrystals to ordered nano/microcrystal arrays, such as local rate probing in a flowing liquid.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/smll.201904298DOI Listing
October 2019

On the decay time of upconversion luminescence.

Nanoscale 2019 Mar;11(11):4959-4969

Department of Applied Physics, KTH Royal Institute of Technology, S-10691, Stockholm, Sweden.

In this study, we systematically investigate the decay characteristics of upconversion luminescence (UCL) under anti-Stokes excitation through numerical simulations based on rate-equation models. We find that a UCL decay profile generally involves contributions from the sensitizer's excited-state lifetime, energy transfer and cross-relaxation processes. It should thus be regarded as the overall temporal response of the whole upconversion system to the excitation function rather than the intrinsic lifetime of the luminescence emitting state. Only under certain conditions, such as when the effective lifetime of the sensitizer's excited state is significantly shorter than that of the UCL emitting state and of the absence of cross-relaxation processes involving the emitting energy level, the UCL decay time approaches the intrinsic lifetime of the emitting state. Subsequently, Stokes excitation is generally preferred in order to accurately quantify the intrinsic lifetime of the emitting state. However, possible cross-relaxation between doped ions at high doping levels can complicate the decay characteristics of the luminescence and even make the Stokes-excitation approach fail. A strong cross-relaxation process can also account for the power dependence of the decay characteristics of UCL.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c8nr10332aDOI Listing
March 2019

Fast upconversion super-resolution microscopy with 10 μs per pixel dwell times.

Nanoscale 2019 Jan;11(4):1563-1569

Centre for Optical and Electromagnetic Research, South China Academy of Advanced Optoelectronics, South China Normal University, 510006 Guangzhou, China.

Multi-photon upconversion super-resolution microscopy is a recently proposed imaging modality, based on lanthanide-doped nanocrystals, which can emit visible emission upon low-intensity near-infrared excitation. This imaging modality exhibits many advantages, including increased imaging depth, high signal-to-noise ratio, low phototoxicity, and high photostability. However, two factors seriously restrict its scanning speed, sometimes even to an intolerable degree; the long lanthanide emission lifetime and the low brightness. For proper imaging, pixel dwell times of several milliseconds are often required. In this work, a facile strategy is proposed to overcome these two obstacles. By adopting a high sensitizer (Yb3+) doping strategy for upconversion nanocrystals, their emission intensity is greatly increased and their emission transients are significantly accelerated, without losing the emission depletion efficiency induced by the depletion laser. This enables the implementation of a very fast upconversion stimulated emission depletion super-resolution microscopy with a scanning speed of 10 μs per pixel. This work opens the possibility for upconversion super-resolution microscopy to capture vital biological activities in real time.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c8nr08986hDOI Listing
January 2019

One-scan fluorescence emission difference nanoscopy developed with excitation orthogonalized upconversion nanoparticles.

Nanoscale 2018 Dec 14;10(45):21025-21030. Epub 2018 Nov 14.

Centre for Optical and Electromagnetic Research, Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, 510006 Guangzhou, China.

We experimentally realized one-scan fluorescence emission difference nanoscopy (FED) by simultaneously imaging two different color emissions of NaYF:[email protected]@NaYF:Yb/Tm upconversion nanoparticles. Under the irradiation of two synchronized laser beams, a solid 940 nm beam and a hollow 808 nm beam, green emission of Er and blue emission of Tm can be orthogonally generated and collected. After simple subtraction, a resulting super-resolution image featuring 54 nm resolution was obtained. This strategy of excitation orthogonality would greatly improve the imaging speed and the applicability of FED nanoscopy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c8nr07017bDOI Listing
December 2018

Sulfuric Acid Assisted Preparation of Red-Emitting Carbonized Polymer Dots and the Application of Bio-Imaging.

Nanoscale Res Lett 2018 Sep 10;13(1):272. Epub 2018 Sep 10.

Centre for Optical and Electromagnetic Research, Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, 510006, China.

Red-emitting carbonized polymer dots (CPDs) was prepared from p-phenylenediamine (p-PD) aqueous solution with the assistance of sulfuric acid (HSO), and the optical properties and bio-imaging application were studied in this paper. Compared with other strong acids-assisted systems, SA-CPDs (prepared from HSO-assisted system, average diameter is ~ 5 nm) is the brightest. The photoluminescence Quantum Yields (QYs) is 21.4% (in water), and the product yield is 16.5%. SA-CPDs aqueous solution emits at 600 nm when excited by the light from 300 to 580 nm. The emission wavelength is independent on the excitation wavelength. Formation energies of CPDs in two ways were calculated to show that longitudinal growth (forming polymers) is difficult, and the transverse growth (forming CPDs) is easy. In addition, the two-photon photoluminescence properties (emitting at 602 nm when excited by 850 nm femtosecond pulse laser) of SA-CPDs were also utilized in the experiments for HeLa cells staining and shown to have potential applications in bio-imaging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s11671-018-2657-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6134856PMC
September 2018

Non-bleaching fluorescence emission difference microscopy using single 808-nm laser excited red upconversion emission.

Opt Express 2017 Dec;25(25):30885-30894

Optical super-resolution microscopy has become a powerful technique to help scientists to monitor the sample of interest at nanoscale. Fluorescence emission difference (FED) microscopy, a very facile super-resolution method, does not require high depleting laser intensity and is independent on the species of agents, which makes FED microscopy possess great potential. However, to date, the biomarkers applied in FED microscopy usually suffer from a photo-bleaching problem. In this work, by introducing Er activated upconverting nanoparticles with red-color emission and non-photobleaching properties, we demonstrate nonbleaching super-resolution imaging with FED microscopy. The dopant neodymium ions (Nd) can work as highly efficient sensitizing ions and enable near infrared 808-nm CW laser excitation of relatively low power, which would potentially reduce high intensity/short-wavelength light induced tissue damage. Both simulations and experiments on monodispersed NaYF:Nd/Yb/[email protected]:Nd UCNPs also indicate that the easy saturation of the multiphoton properties of these UCNPs is beneficial to resolution enhancement in FED microscopy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.25.030885DOI Listing
December 2017

Ruthenium complex-modified carbon nanodots for lysosome-targeted one- and two-photon imaging and photodynamic therapy.

Nanoscale 2017 Dec;9(47):18966-18976

MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, Guangzhou, China.

Nanohybrids can in most cases kill cancer cells more efficiently as compared with free photosensitizers. In this work, we constructed nanohybrid [email protected] composed of carbon nanodots (CDs) and a phosphorescent Ru(ii) complex (Ru1) for one- and two-photon photodynamic therapy of cancer. The photosensitizer and imaging agent Ru1 is decorated onto the nanocarrier CDs covalently. Ru1 and [email protected] can penetrate into cancer cells through an energy-dependent mechanism and endocytosis, respectively. Both Ru1 and [email protected] are capable of lysosome-targeted phosphorescence imaging and photodamage under either 450 nm (one-photon) or 810 nm (two-photon) excitation. Conjugation with CDs can increase the cellular uptake efficacy of Ru1. Mechanism investigations show that both Ru1 and [email protected] can induce apoptosis through generation of reactive oxygen species and cathepsin-initiated apoptotic signaling pathways. Upon two-photon excitation, [email protected] show better penetrability, as well as higher inhibitory effects on cancer cell growth in both 2D cell and 3D multicellular tumor spheroid models. Our work provides an effective strategy for the construction of multifunctional imaging and phototherapeutic nanohybrids for the treatment of cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c7nr05349eDOI Listing
December 2017

Achieving high-efficiency emission depletion nanoscopy by employing cross relaxation in upconversion nanoparticles.

Nat Commun 2017 10 20;8(1):1058. Epub 2017 Oct 20.

Centre for Optical and Electromagnetic Research, South China Academy of Advanced Optoelectronics, South China Normal University, 510006, Guangzhou, P.R. China.

Stimulated emission depletion microscopy provides a powerful sub-diffraction imaging modality for life science studies. Conventionally, stimulated emission depletion requires a relatively high light intensity to obtain an adequate depletion efficiency through only light-matter interaction. Here we show efficient emission depletion for a class of lanthanide-doped upconversion nanoparticles with the assistance of interionic cross relaxation, which significantly lowers the laser intensity requirements of optical depletion. We demonstrate two-color super-resolution imaging using upconversion nanoparticles (resolution ~ 66 nm) with a single pair of excitation/depletion beams. In addition, we show super-resolution imaging of immunostained cytoskeleton structures of fixed cells (resolution ~ 82 nm) using upconversion nanoparticles. These achievements provide a new perspective for the development of photoswitchable luminescent probes and will broaden the applications of lanthanide-doped nanoparticles for sub-diffraction microscopic imaging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-017-01141-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5648820PMC
October 2017

Carbohydrates as Fat Replacers.

Annu Rev Food Sci Technol 2017 02;8:331-351

The Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, Indiana 47907; email:

The overconsumption of dietary fat contributes to various chronic diseases, which encourages attempts to develop and consume low-fat foods. Simple fat reduction causes quality losses that impede the acceptance of foods. Fat replacers are utilized to minimize the quality deterioration after fat reduction or removal to achieve low-calorie, low-fat claims. In this review, the forms of fats and their functions in contributing to food textural and sensory qualities are discussed in various food systems. The connections between fat reduction and quality loss are described in order to clarify the rationales of fat replacement. Carbohydrate fat replacers usually have low calorie density and provide gelling, thickening, stabilizing, and other texture-modifying properties. In this review, carbohydrates, including starches, maltodextrins, polydextrose, gums, and fibers, are discussed with regard to their interactions with other components in foods as well as their performances as fat replacers in various systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1146/annurev-food-030216-030034DOI Listing
February 2017

Effects of high-temperature pressure cooking and traditional cooking on soymilk: Protein particles formation and sensory quality.

Food Chem 2016 Oct 13;209:50-6. Epub 2016 Apr 13.

College of Food Science and Nutritional Engineering, China Agricultural University, No. 17, Qinghua Donglu, Haidian District, Beijing 100083, China. Electronic address:

This study focused on the effect of high-temperature pressure cooking on the sensory quality of soymilk. Soymilk was prepared by high-temperature pressure cooking (105-125°C and 0.12-0.235MPa) and traditional cooking (97°C and 0.1MPa). The size distribution and composition of protein particles and the rheological properties of soymilk were compared. Results showed that the content of protein particles and the average size of soymilk particles were higher in high-temperature pressure cooking than in traditional cooking (p<0.05). High-temperature pressure cooking affected soymilk protein denaturation and favored protein aggregation. Similar to traditional soymilk, soymilk cooked at 115°C was categorized as a Newtonian fluid but was found with increased viscosity in the rheological test. Soymilk cooked at 115°C for 10min exhibited a homogeneous, smooth, and creamy texture with a high acceptability in the sensory test.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2016.04.026DOI Listing
October 2016

Evaluation of the aroma quality of Chinese traditional soy paste during storage based on principal component analysis.

Food Chem 2014 May 27;151:532-8. Epub 2013 Nov 27.

College of Food Science and Nutritional Engineering, China Agricultural University, 17 Qinghuadonglu Rd., Beijing 100083, China. Electronic address:

Soy paste, a fermented soybean product, is widely used for flavouring in East and Southeast Asian countries. The characteristic aroma of soy paste is important throughout its shelf life. This study extracted volatile compounds via headspace solid-phase microextraction and conducted a quantitative analysis of 15 key volatile compounds using gas chromatography and gas chromatography-mass spectrum analysis. Changes in aroma content during storage time were analyzed using an acceleration model (40 °C, 28 days). In the 28 days of storage, results showed that among key soy paste volatile compounds, alcohol and aldehyde contents decreased by 35% and 26%, respectively. By contrast, acid, ester, and heterocycle contents increased by 130%, 242%, and 15%, respectively. The overall odour type transformed from a floral to a roasting aroma. According to sample clustering in the principal component analysis, the storage life of soy paste could be divided into three periods. These three periods represent the floral, roasting, and pungent aroma types of soy paste.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.foodchem.2013.11.095DOI Listing
May 2014
-->