Abstract：
BACKGROUND: Single-wall carbon nanotubes (SWCNT) dispersed in water with the help of sodium dodecyl sulfate (SDS) surfactants exhibit a temperature dependent near infrared (NIR) exciton spectrum. Due to their biocompatibility and NIR spectrum falling within the transparent window for biological tissue, SWCNTs hold potential for sensing temperature inside cells. Here, we seek to elucidate the mechanism responsible for this temperature dependence, focusing on changes in the water coverage of the SWCNT as the surfactant structure changes with temperature. We compare optical absorption spectra in the UV-Vis-IR range and fully atomistic molecular dynamics (MD) simulations. The observed temperature dependence of the spectra for various SWCNTs may be attributed to changes in the dielectric environment and its impact on excitons. MD simulations reveal that the adsorbed SDS molecules effectively shield the SWCNT, with ~ 70% of water molecules removed from the first two adlayers; this coverage shows a modest temperature dependence. Although we are not able to directly demonstrate how this influences the NIR spectrum, this represents a potential pathway given the strong influence of the water environment on the excitons in SWCNTs.
METHODS: Optical absorption measurements were carried out in the UV-Vis-NIR range using a Varian Cary 5000 spectrophotometer in a temperature-controlled environment. PeakFit™ v. 4.06 was used as peak-fitting program in the spectral range 900-1400 nm (890-1380 meV) as a function of the temperature. Fully atomistic molecular dynamics simulations were conducted using the NAMD2 package. The CHARMM force field comprising two-body bond stretching, three-body angle deformation, four-body dihedral angle deformation, and nonbonded interactions (electrostatic and Lennard-Jones 6-16 potentials) was employed.
METHODS: Optical absorption measurements were carried out in the UV-Vis-NIR range using a Varian Cary 5000 spectrophotometer in a temperature-controlled environment. PeakFit™ v. 4.06 was used as peak-fitting program in the spectral range 900-1400 nm (890-1380 meV) as a function of the temperature. Fully atomistic molecular dynamics simulations were conducted using the NAMD2 package. The CHARMM force field comprising two-body bond stretching, three-body angle deformation, four-body dihedral angle deformation, and nonbonded interactions (electrostatic and Lennard-Jones 6-16 potentials) was employed.
摘要：
背景：借助十二烷基硫酸钠（SDS）表面活性剂分散在水中的单壁碳纳米管（SWCNT）表现出温度依赖性近红外（NIR）激子光谱。由于它们的生物相容性和近红外光谱落在生物组织的透明窗口内，SWCNT具有感测电池内部温度的潜力。这里,我们试图阐明这种温度依赖性的机制，重点关注SWCNT的水覆盖率随着表面活性剂结构随温度变化而变化。我们比较了UV-Vis-IR范围内的光学吸收光谱和完全原子分子动力学（MD）模拟。观察到的各种SWCNT光谱的温度依赖性可能归因于介电环境的变化及其对激子的影响。MD模拟表明，吸附的SDS分子有效地屏蔽了SWCNT，从前两个adlayer中去除约70％的水分子；这种覆盖范围显示出适度的温度依赖性。虽然我们无法直接证明这对近红外光谱的影响，考虑到水环境对SWCNT中激子的强烈影响，这代表了潜在的途径。
方法:使用VarianCary5000分光光度计在温控环境中在UV-Vis-NIR范围内进行光吸收测量。使用PeakFit™v.4.06作为温度的函数在900-1400nm(890-1380meV)的光谱范围内的峰拟合程序。使用NAMD2包进行全原子分子动力学模拟。CHARMM力场包括两体结合拉伸，三体角度变形，四体二面角变形，并采用非键合相互作用（静电和Lennard-Jones6-16电位）。
方法:使用VarianCary5000分光光度计在温控环境中在UV-Vis-NIR范围内进行光吸收测量。使用PeakFit™v.4.06作为温度的函数在900-1400nm(890-1380meV)的光谱范围内的峰拟合程序。使用NAMD2包进行全原子分子动力学模拟。CHARMM力场包括两体结合拉伸，三体角度变形，四体二面角变形，并采用非键合相互作用（静电和Lennard-Jones6-16电位）。
