镅 | 7440-35-9

• 物质功能分类: 无机化工 - 单质
• 分子结构分类: 无机化合物 - 均相金属化合物 - 均相锕系化合物
• 中文名称: 镅
• 英文名称: americium
• CAS: 7440-35-9
• 化学式: Am
• 分子量: 243.061
• InChiKey: LXQXZNRPTYVCNG-UHFFFAOYSA-N

物化性质

• 熔点：
  1175℃
• 沸点：
  bp (calc) 2067°
• 密度：
  13.671
• 溶解度：
  溶于酸溶液
• 颜色/状态：
  Silvery metal /Zero valence americium/
• 稳定性/保质期：

  银白色金属，有光泽，软而韧，在空气中会变暗，不具磁性，且具有强放射性。有两种同素异形体：α-型为六方结构，熔点高于800℃，沸点为2600℃，密度11.7克/立方厘米；加热至1074℃时会转化为β-型；β-型则为面心结构，其熔点为1075℃。化学性质活泼，容易溶解于稀无机酸中。所有镅的同位素均通过人工制得，新制备的镅半衰期约为432年。

计算性质

• 辛醇/水分配系数(LogP)：
  0.0
• 重原子数：
  1
• 可旋转键数：
  0
• 环数：
  0.0
• sp3杂化的碳原子比例：
  0.0
• 拓扑面积：
  0
• 氢给体数：
  0
• 氢受体数：
  0

ADMET

代谢

锕系元素中的锕与蛋白质有结合作用，并可能形成与各种无机阴离子如碳酸根、磷酸根以及有机酸如柠檬酸和乳酸的复合物。这类相互作用在所有暴露途径中都是预期的。

The metabolism of americium involves binding interactions with proteins and probably complex formation with various inorganic anions, such as carbonate and phosphate, and carboxylic acids, such as citrate and lactate. These types of interactions would be expected for all routes of exposure.

来源:Hazardous Substances Data Bank (HSDB)

代谢

镅可以通过摄入、吸入和皮肤接触被吸收。在体内，它主要分布到肝脏，以及骨骼和骨骼肌。镅的代谢涉及与蛋白质的结合相互作用，可能还会与各种无机阴离子，如碳酸根和磷酸根，以及羧酸，如柠檬酸盐和乳酸盐形成复合物。镅通过粪便和尿液排出。

Americium can be absorbed following ingestion, inhalation, and dermal exposure. In the body it distributes primarily to the liver, as well as to the bone and skeletal muscle. The metabolism of americium involves binding interactions with proteins and probably complex formation with various inorganic anions, such as carbonate and phosphate, and carboxylic acids, such as citrate and lactate. Americium is excreted in faeces and urine. (L1843)

来源:Toxin and Toxin Target Database (T3DB)

毒理性

• 毒性总结

镅毒性主要来自于放射性衰变过程中释放的α粒子所造成的损害。这种α粒子在组织中的穿透性非常有限，因此，细胞损伤仅发生在被困住的镅附近的区域。镅产生的电离辐射会导致细胞损伤，包括DNA断裂、精确或不精确的修复、细胞凋亡、基因突变、染色体改变和遗传不稳定。这会导致正常细胞和组织的稳态丧失，并发展成恶性肿瘤。那些不直接损伤DNA的电离辐射可以产生反应性氧中间体，这些中间体直接影响p53的稳定性，p53是细胞周期调节中一个重要的酶，并通过DNA复制期间的错配导致DNA单个碱基的氧化损伤和点突变。

Americium toxicity results primarily from the damage done by the alpha particle emitted during radioactive decay. This alpha particle has very limited penetration in tissue, and hence, the cellular damage occurs only in the immediate vicinity of the sequestered americium. The ionizing radiation produced by americium causes cellular damage that includes DNA breakage, accurate or inaccurate repair, apoptosis, gene mutations, chromosomal change, and genetic instability. This leads to loss of normal cell and tissue homeostasis, and development of malignancy. Ionizing radiation that does not directly damage DNA can produce reactive oxygen intermediates that directly affect the stability of p53, an important enzyme in cell-cycle regulation, and produce oxidative damage to individual bases in DNA and point mutations by mispairing during DNA replication. (L1837)

来源:Toxin and Toxin Target Database (T3DB)

毒理性

• 致癌性证据

混合α粒子发射体（镭-224、镭-226、钍-227、钍-228、钍-230、钍-232、镎-237、钚-238、钚-239（与钚-240一起）、镅-241、锔-244、锎-249和锎-252）在实验动物中具有致癌性的证据是充分的。/镭、钚、镅、锔、锎/

There is sufficient evidence in experimental animals for the carcinogenicity of mixed alpha-particle emitters (radium-224, radium-226, thorium-227, thorium-228, thorium-230, thorium-232, neptunium-237, plutonium-238, plutonium-239 (together with plutonium- 240), americium-241, curium-244, californium-249 and californium-252). /Radium, Plutonium, Americium, Curium, Californium/

来源:Hazardous Substances Data Bank (HSDB)

毒理性

• 致癌性证据

内化的发射α粒子的放射性核素对人类是致癌的（第1组）。在做出这一总体评估时，工作组考虑了以下因素：无论其来源如何，放射性核素发射的α粒子都会产生相同的二次电离模式和相同的生物分子局部损伤模式，包括DNA。在体外观察到的这些效应包括DNA双链断裂、染色体畸变、基因突变和细胞转化。所有发射α粒子的放射性核素，包括氡-222及其衰变产物，都已经在人类和实验动物中被证明能引起癌症。无论其来源如何，放射性核素发射的α粒子已被证明能在体内的人类循环淋巴细胞中引起染色体畸变和基因突变。人类和实验动物的研究证据表明，不同放射性核素衰变期间发射的α粒子对相同组织——例如肺细胞或骨表面——产生的相似剂量会产生相同类型的非肿瘤效应和癌症。/内化的α发射体/

Internalized radionuclides that emit alpha-particles are carcinogenic to humans (Group 1). In making this overall evaluation, the Working Group took into consideration the following: Alpha-particles emitted by radionuclides, irrespective of their source, produce the same pattern of secondary ionizations and the same pattern of localized damage to biological molecules, including DNA. These effects, observed in vitro, include DNA doublestrand breaks, chromosomal aberrations, gene mutations and cell transformation. All radionuclides that emit alpha-particles and that have been adequately studied, including radon-222 and its decay products, have been shown to cause cancer in humans and in experimental animals. Alpha-particles emitted by radionuclides, irrespective of their source, have been shown to cause chromosomal aberrations in circulating lymphocytes and gene mutations in humans in vivo. The evidence from studies in humans and experimental animals suggests that similar doses to the same tissues - for example lung cells or bone surfaces - from alpha- particles emitted during the decay of different radionuclides produce the same types of non-neoplastic effects and cancers. /Internalized alpha-emitters/

来源:Hazardous Substances Data Bank (HSDB)

毒理性

• 致癌物分类

内化的发射α粒子的放射性核素对人类是致癌的（第1组）（L2150）。镅-243经历α衰变。

Internalized radionuclides that emit α-particles are carcinogenic to humans (Group 1) (L2150). Americium-243 undergoes alpha decay.

来源:Toxin and Toxin Target Database (T3DB)

毒理性

• 健康影响

镅的放射性可导致癌症，特别是骨癌，因为它已知会在骨骼中积累。大量接触镅也可能损害肺、肝脏和甲状腺。

Americium's radioactivity can cause cancer, especially of the bone, where it is known to accumulate. Exposure to large amount of americium may also damage the lungs, liver, and thyroid. (L1843)

来源:Toxin and Toxin Target Database (T3DB)

吸收、分配和排泄

一个38岁的白人男性因急性意外吸入6.3 kBq的镅-241而受到监测，监测期持续了2,135天，期间定期进行体内测量，以评估肺、肝脏和骨骼中的放射性活度。肺部清除过程用双室指数衰减模型描述，其半衰期分别为110天和10,000天。观察到的镅-241在肝脏（72 Bq）和骨骼（170 Bq）中的摄取量显著高于国际放射性辐射防护委员会（ICRP）模型预测的肝脏（5 Bq）和骨骼（8 Bq）的摄取量。肝脏中的半衰期大约为850天。基于头部、手腕和膝盖计数的骨骼活动估计在整个监测期间通常在25%以内一致。骨骼的半衰期大约为20,000天。/镅-241/

A 38-y-old Caucasian male who suffered an acute accidental inhalation intake of 6.3 kBq of americium-241 was monitored over 2,135 days using periodic in vivo measurements of the activity in the lungs, liver, and skeleton. Lung clearance was described by a two-compartment exponential model with half-times of 110 days and 10,000 days. The observed uptake of americium-241 in the liver (72 Bq) and skeleton (170 Bq) was significantly greater than predicted by the ICRP models for liver (5 Bq) and skeleton (8 Bq). The half-time in the liver was approximately 850 d. Estimates of skeletal activity based on head, wrist, and knee counts generally agreed within 25% over the course of the monitoring period. The half-time in the skeleton was approximately 20,000 d. /Americium-241/

来源:Hazardous Substances Data Bank (HSDB)

吸收、分配和排泄

一位成年工人在吸入钚和锕-241二氧化物（分别为239-PuO2和241-AmO2）气溶胶后，从暴露后第7天开始的胸部放射性计数，通过外部辐射探测器测定，显示锕-241从胸部区域的生物半衰期为11天（占80%）和920天（占20%）。这些估计值被认为反映了从肺部到系统部位的清除。然而，估计的粪便排泄大约为肺内估计的锕-241初始沉积量的50%，这表明大量的机械传输到胃肠道，这是吸入大颗粒的典型现象。外部计数在事故后第913天在头骨中检测到锕-241，这表明锕-241已转移到骨骼中。 /钚和锕二氧化物/

... An adult worker inhaled aerosols of plutonium and americium dioxides (239-PuO2 and 241-AmO2). Thoracic counts of radioactivity that were determined by an external radiation detector starting 7 days after the exposure showed that 241-Am was removed from the chest area with biological half-times of 11 (80%) and 920 (20%)days. These estimates were assumed to reflect clearance from the lung to systemic compartments. However, fecal excretion was estimated to be approximately 50% of the estimated initial deposit of americium-241 in the lung, suggesting that extensive mechanical transport to the gastrointestinal tract, typical of inhaled large particles, may have occurred. External counting also detected Americium-241 in the skull on day 913 post accident, suggesting that americium-241 was transferred to the skeleton. /Plutonium and americium dioxides/

来源:Hazardous Substances Data Bank (HSDB)

吸收、分配和排泄

从人体暴露的可用信息表明，含有气态镅的颗粒物沉积在呼吸道中，在一定程度上通过粘膜纤毛活动被清除，然后被吞下或排出。/气态镅/

Available information from human exposures indicates that airborne americium-containing particles are deposited in the respiratory tract, cleared to some extent via mucociliary action, and swallowed or expelled. /Airborne americium/

来源:Hazardous Substances Data Bank (HSDB)

吸收、分配和排泄

一位成年工作者吸入了混合的锔和镅的氧化物（244-CmO2和241-AmO2）（244-Cm:241-Am气溶胶比例，3:1），导致大约450 nCi（16.6 kBq）的放射性物质沉积在肺部，或者大约112 nCi（4.1 kBq）的241-Am。受试者的胸部计数表明，总放射性物质在肺部保留，其半衰期（即衰变校正后）为28天；然而，没有报告每个同位素从肺部排出的数据。胸部区域的大部分排出是通过在粪便中回收放射性物质来计算的，这与将沉积的活动性机械清除到胃肠道的现象一致。这种情况下系统吸收的证据是在尿液中检测到241-Am；大约1.1 nCi（41 Bq，沉积活性的1%）的241-Am在365天内通过尿液排出，其半衰期为35天。/锔和镅的混合氧化物/

... An adult worker inhaled mixed oxides of curium and americium dioxides (244-CmO2 and 241-AmO2) (244-Cm:241-Am airborne ratio, 3:1), which resulted in the deposition of approximately 450 nCi (16.6 kBq) of radioactivity in the lungs, or approximately 112 nCi (4.1 kBq) of 241-Am. Chest counts of the subject indicated that total radioactivity was retained in the lungs with a half-time (i.e., decay-corrected) of 28 days; however, data on the elimination of each isotope from the lung were not reported. Most of the elimination from the chest area was accounted for by recovery of radioactivity in the feces, consistent with mechanical clearance of the deposited activity to the gastrointestinal tract. Evidence for systemic absorption in this case was the detection of 241-Am in urine; approximately 1.1 nCi (41 Bq, 1% of the deposited activity) of 241-Am was excreted in urine in 365 days, with a half-time of 35 days. /Mixed oxides of curium and americium/

来源:Hazardous Substances Data Bank (HSDB)

制备方法与用途

简介

镅（Americium，台湾译作鋂）是一种放射性超铀元素，符号为Am，原子序数为95。镅属于锕系元素，在元素周期表中位于镧系元素铕之下，并以发现它的美洲大陆命名。

性质

镅是一种柔软的放射性金属，外表呈银白色。最常见的是241Am和243Am这两种同位素。在化合物中，特别是溶液中，镅通常表现出+3价态，但也有从+2到+7之间的其他氧化态，可通过吸收光谱测量来区分。由于辐射变晶效应，镅固体和其化合物的晶体结构本身含有缺陷，这些缺陷随时间增加，导致物质属性的变化。

合成

虽然铀是反应堆中最常见的物质，但镅并不是直接从铀生成的，而是通过以下过程从钚同位素239Pu产生：

[ 239\text{Pu} + 2 \text{n} \xrightarrow{\beta^-} 241\text{Am} ]

反应信息

• 作为反应物：
  描述：

  镅 在 HCl 作用下， 以 盐酸 为溶剂， 生成 氢气
  参考文献：
  名称：

  Gmelin Handbuch der Anorganischen Chemie, Gmelin Handbook: Np: TrU.B1, 1.3, page 57 - 67

  摘要：

  DOI：
• 作为产物：
  描述：

  americium trifluoride 在 Ba or Li 作用下， 以 not given 为溶剂， 生成 镅
  参考文献：
  名称：

  meric金属的晶体结构，热膨胀和熔点

  摘要：

  详细讨论了制备毫克量的纯净，良好结晶的a金属的方法。介绍了一种用于小型放射性样品的多功能高低温X射线粉末相机。

  DOI：

  10.1016/0022-1902(62)80246-2

文献信息

• Americium chloro-complexes
  作者：K. W. Bagnall、J. B. Laidler、M. A. A. Stewart

  DOI：10.1039/j19680000133

  日期：——

  Americium(III) tetrachloro- and hexachloro-complexes, CsAmCl4(hydrated and anhydrous), Cs2NaAmCl6, and Cs3AmCl6 have been prepared. Their infrared spectra and some X-ray powder results are reported; the analyses of these compounds, and of the americium(V) chloro-complex, Cs3AmO2Cl4, are consistent with the new value (433 years) for the half-life of 241Am.

  制备了（（III）四氯和六氯配合物，CsAmCl 4（水合和无水），Cs 2 NaAmCl 6和Cs 3 AmCl 6。报告了它们的红外光谱和一些X射线粉末结果。这些化合物以及a（V）氯配合物Cs 3 AmO 2 Cl 4的分析与241 Am半衰期的新值（433年）一致。
• Actinide(lanthanide)-noble metal alloy phases, preparation and properties
  作者：B. Erdmann、C. Keller

  DOI：10.1016/0022-4596(73)90119-9

  日期：1973.5

  extremely purified hydrogen. Alloy phases of composition AB2, AB3, and/or AB5 have been identified, most of which crystallize in the Cu2Mg, Cu3Au, Ni3Ti, Cd3Mg, Ni5U, and Pt5Sm types of structure. The lattice constants of isostructural series show a trend which also is known for the radii of the actinide elements. Analytical data, self-irradiation effects, magnetic data, nuclear γ resonance spectra, and

  of系（AThCm）-含铂，钯，铑和铱（B）的贵金属相-和镧系元素-贵金属与铂和钯的相，是通过在以下条件下还原相应的氧化物或氟化物来制备的贵金属由极其纯净的氢气制成。已经鉴定出成分为AB 2，AB 3和/或AB 5的合金相，其中大多数在Cu 2 Mg，Cu 3 Au，Ni 3 Ti，Cd 3 Mg，Ni 5 U和Pt 5中结晶。Sm类型的结构。同构系列的晶格常数显示出一种趋势，这种趋势也因act系元素的半径而为人所知。所选合金相的分析数据，自辐照效应，磁数据，核γ共振光谱和热行为，以及其他一些过渡元素和主族元素（例如Zr，Hf，Nb，Ta， MgBa，据报道。
• Evidence for covalence in a N-donor complex of americium(iii)
  作者：Christian Adam、Peter Kaden、Björn B. Beele、Udo Müllich、Sascha Trumm、Andreas Geist、Petra J. Panak、Melissa A. Denecke

  DOI：10.1039/c3dt50953b

  日期：——

  The molecular origin of the selectivity of N-donor ligands, such as alkylated bis-triazinyl pyridines (BTPs), for actinide complexation in the presence of lanthanides is still largely unclear. NMR investigations of an Am(nPrBTP)33+ complex with a 15N labelled ligand showed that it exhibits large differences in 15N chemical shift for coordinating N-atoms in comparison to both lanthanide(III) complexes and the free ligand. The temperature dependence of NMR chemical shifts observed for this complex indicates a weak paramagnetism. This fact and the observed large chemical shift for bound nitrogen atoms allow us to conclude that metal–ligand bonding in the reported Am(III) N-donor complex has a larger share of covalence than in lanthanide complexes. This may account for the observed selectivity.

  N-供体配体（如烷基化双三嗪基吡啶（BTP））在锕系元素复合物中对镧系元素存在的选择性分子来源仍然很大程度上不明确。对一个带有15N标记配体的Am(nPrBTP)33+复合物的NMR研究表明，与镧系(III)复合物和游离配体相比，该复合物的配位氮原子的15N化学位移差异显著。观察到的该复合物NMR化学位移的温度依赖性表明存在弱的顺磁性。这一事实以及与配位氮原子相关的显著化学位移使我们得出结论，即在所报道的Am(III) N-供体复合物中，金属-配体间的结合具有比镧系复合物更大的共价特性。这可能解释了观察到的选择性。
• Alkaline oxidation of americium; preparation and reactions of Am(IV) hydroxide
  作者：R.A. Penneman、J.S. Coleman、T.K. Keenan

  DOI：10.1016/0022-1902(61)80199-1

  日期：1961.4

  in sulphuric acid giving Am(VI) and Am(III), with a minimum of half of the Am(V) produced from the simple disproportionation of Am(IV) being consumed by a consecutive reaction: Am(IV) + Am(V) + Am(VI) + Am(III). Revision from + 0·4 to at least −0·5 V is suggested for the value of the standard potential of the Am(OH)3, Am(OH)4 couple.

  在稀碱中通过次氯酸盐氧化将Am（OH）3的粉红色浆液定量转化为四价a的黑色氢氧化物（或含水氧化物）。以前尚未报道过从水溶液中制备四价a。该物质溶于硝酸或高氯酸，并根据以下公式歧化：2Am（IV）= Am（V）+ Am（III）。它溶解于硫酸中，得到Am（VI）和Am（III），通过连续反应消耗的Am（IV）的简单歧化产生的Am（V）的至少一半被以下连续反应消耗：Am（IV）+ Am （V）+ Am（VI）+ Am（III）。建议将Am（OH）3和Am（OH）4对的标准电势值从+ 0·4更改为至少−0·5V 。
• A test for oxidation of actinides in concentrated CsF solutions
  作者：H.P. Holcomb

  DOI：10.1016/0022-1902(67)80119-2

  日期：1967.12

  A chemical test was devised to differentiate between tracer concentrations of the actinide (III) state and higher oxidation states in 12–15 M CsF. Attempts to oxidize Cm(III) and Cf(III) with sodium perxenate in this matrix were unsuccessful although Am(III) was readily oxidized.

  设计了一种化学测试，以区分示踪剂浓度的act系元素（III）状态和12–15 M CsF中的较高氧化态。尽管Am（III）容易被氧化，但用该过氧化钠在该基质中氧化Cm（III）和Cf（III）的尝试仍未成功。