二硫化钼（MoS₂）这类二维材料为什么受关注？
Why are 2D materials like MoS₂ interesting?
单层 MoS₂ 是直接带隙半导体，可作超薄晶体管与催化剂；与石墨烯互补，拓展了二维电子学。
Monolayer MoS₂ is a direct-gap semiconductor useful as ultrathin transistors and catalysts; it complements graphene in 2D electronics.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#二维材料 #MoS2 #半导体
组成相同的 CdSe 量子点,粒径从约 2 nm 增大到 6 nm 时荧光由蓝色变为红色,其化学根源是什么?
For CdSe quantum dots of identical composition, why does the fluorescence shift from blue to red as the diameter grows from about 2 nm to 6 nm?
当 CdSe 颗粒直径小于其激子玻尔直径(约 11 nm,对应玻尔半径约 5.6 nm)时,电子与空穴受到三维量子限域,准连续能带分裂为分立能级,有效带隙随尺寸减小而展宽。小颗粒带隙大,发射短波蓝光;颗粒长大,限域减弱,带隙收窄,发射红移至橙红。合成上通过控制成核后的熟化时间与温度来调节粒径,即可实现发射波长的连续调谐。
When the particle diameter falls below the exciton Bohr diameter of CdSe (about 11 nm, corresponding to a Bohr radius near 5.6 nm), electrons and holes experience three-dimensional quantum confinement and the quasi-continuous bands split into discrete levels, widening the effective gap as size decreases. Small particles have large gaps and emit short-wavelength blue light; as particles grow, confinement weakens, the gap narrows, and emission red-shifts toward orange-red. Controlling post-nucleation ripening time and temperature adjusts particle size, enabling continuous tuning of the emission wavelength.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Brus L. E., J. Chem. Phys., 1984, 80, 4403;Murray C. B. 等, J. Am. Chem. Soc., 1993, 115, 8706
Brus L. E., J. Chem. Phys., 1984, 80, 4403; Murray C. B. et al., J. Am. Chem. Soc., 1993, 115, 8706
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1021/ja00072a025
#量子限域 #带隙调谐
氧化石墨烯膜为什么能用来海水淡化？
Why can graphene-oxide membranes be used for desalination?
氧化石墨烯层间有纳米级通道，水分子可快速通过而截留盐离子；调节层间距还能控制选择性。
Graphene oxide has nanochannels between layers that let water pass fast while rejecting salt ions; tuning the spacing controls selectivity.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#石墨烯 #纳滤 #海水淡化
碳纳米管为什么又轻又强还能导电？
Why are carbon nanotubes light, strong and conductive?
卷曲的石墨烯sp²碳网络赋予极高强度与导电性，中空结构又极轻；单壁管可呈金属性或半导体性。
The rolled graphene sp² network gives strength and conductivity, while the hollow structure is very light; single-wall tubes can be metallic or semiconducting.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#碳纳米管 #纳米材料 #导电
脂质体怎么当药物的“快递员”？
How do liposomes act as drug couriers?
磷脂双分子层自组装成空心囊泡，把难溶或易降解的药包在里面，延长循环并帮助靶向递送。
Phospholipid bilayers self-assemble into hollow vesicles that encapsulate hard-to-dissolve or fragile drugs, prolonging circulation and aiding targeting.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#脂质体 #药物递送 #纳米医学
为什么纳米金溶胶会呈现红色,而块体金是金黄色?
Why does colloidal gold appear red while bulk gold looks golden-yellow?
纳米金颗粒尺寸远小于可见光波长时,入射光的电磁场驱动导带电子集体振荡,产生表面等离激元共振,在约520 nm处强烈吸收绿光。透射光因此缺失绿色成分而呈红色。相比之下,块体金的颜色来自5d带向6sp导带的带间跃迁,它选择性吸收蓝绿光使反射光偏金黄,并无尖锐的等离激元峰。颗粒尺寸、形貌和介质折射率都会改变共振峰位置,所以不同粒径的溶胶可从红变紫再到蓝。
When gold nanoparticles are much smaller than the wavelength of visible light, the incident electromagnetic field drives collective oscillation of conduction electrons, producing a localized surface plasmon resonance that strongly absorbs green light around 520 nm. The transmitted light is therefore depleted in green and appears ruby-red. By contrast, the color of bulk gold arises from interband 5d-to-6sp transitions that preferentially absorb blue-green light and tint the reflection golden-yellow, with no sharp plasmon peak. Because particle size, shape, and the refractive index of the medium all shift the resonance peak, sols of different diameters range from red through purple to blue.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Link 与 El-Sayed,《Size and Temperature Dependence of the Plasmon Absorption of Colloidal Gold Nanoparticles》,The Journal of Physical Chemistry B,1999 (DOI: 10.1021/jp984796o)
Link & El-Sayed, 'Size and Temperature Dependence of the Plasmon Absorption of Colloidal Gold Nanoparticles', The Journal of Physical Chemistry B, 1999, DOI: 10.1021/jp984796o
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1021/jp984796o
#纳米金 #表面等离激元共振
用热注入法合成单分散 CdSe 量子点时，为什么前驱体注入后要立即降温，而不是维持高温继续反应？
In the hot-injection synthesis of monodisperse CdSe quantum dots, why must the flask be cooled immediately after precursor injection instead of being kept at the initial high temperature?
注入瞬间单体过饱和度骤升，触发 LaMer 模型中的爆发式成核；随后降温使残余单体只能在已有核上缓慢外延生长，把成核与生长两个阶段分开。若持续高温会不断二次成核，粒径分布变宽，激子吸收与荧光峰随之展宽。快速淬冷配合油酸等配体还能钝化表面悬挂键，保住量子点尺寸依赖的可调发光。
Injection spikes monomer supersaturation and triggers the burst nucleation described by the LaMer model; cooling then lets residual monomers grow slowly onto existing nuclei only, separating nucleation from growth. Sustained heat would cause repeated secondary nucleation, broadening the size distribution and smearing the excitonic absorption and emission peaks. Rapid quenching plus passivating ligands such as oleic acid also caps surface dangling bonds, preserving the size-tunable photoluminescence.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Murray, Norris, Bawendi,《Synthesis and characterization of nearly monodisperse CdE (E = sulfur, selenium, tellurium) semiconductor nanocrystallites》,Journal of the American Chemical Society,1993 (DOI: 10.1021/ja00072a025)
Murray, Norris, Bawendi, 'Synthesis and characterization of nearly monodisperse CdE (E = sulfur, selenium, tellurium) semiconductor nanocrystallites', Journal of the American Chemical Society, 1993, DOI: 10.1021/ja00072a025
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1021/ja00072a025
#纳米材料 #热注入合成
量子点为什么颜色随尺寸变？
Why do quantum dots change color with size?
量子限域使带隙随粒径减小而增大，越小发光越偏蓝；广泛用于 QLED 显示与生物标记。
Quantum confinement widens the band gap as particles shrink, shifting emission bluer; used in QLED displays and bio-labeling.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#量子点 #尺寸效应 #发光