Lead(II) iodide (orlead iodide) is a chemical compound with the formula PbI 2. At room temperature, it is a bright yellow odorless crystalline solid, that becomes orange and red when heated.[11] It was formerly called plumbous iodide.
Lead iodide was formerly employed as a yellow pigment in some paints, with the name iodide yellow. However, that use has been largely discontinued due to its toxicity and poor stability.[16]
Lead iodide prepared from cold solutions usually consists of many small hexagonal platelets, giving the yellow precipitate a silky appearance. Larger crystals can be obtained by exploiting the fact that solubility of lead iodide in water (like those of lead chloride and lead bromide) increases dramatically with temperature. The compound is colorless when dissolved in hot water, but crystallizes on cooling as thin but visibly larger bright yellow flakes, that settle slowly through the liquid — a visual effect often described as "golden rain".[20] Larger crystals can be obtained by autoclaving the PbI 2 with water under pressure at 200 °C.[21]
Even larger crystals can be obtained by slowing down the common reaction. A simple setup is to submerge two beakers containing the concentrated reactants in a larger container of water, taking care to avoid currents. As the two substances diffuse through the water and meet, they slowly react and deposit the iodide in the space between the beakers.[22]
Another similar method is to react the two substances in a gel medium, that slows down the diffusion and supports the growing crystal away from the container's walls. Patel and Rao have used this method to grow crystals up to 30 mm in diameter and 2 mm thick.[23]
The reaction can be slowed also by separating the two reagents with a permeable membrane. This approach, with a cellulose membrane, was used in September 1988 to study the growth of PbI 2 crystals in zero gravity, in an experiment flown on the Space Shuttle Discovery.[24]
PbI 2 is also used as a high-energy photon detector for gamma-rays and X-rays, due to its wide band gap which ensures low noise operation.[4][13][25]
Lead iodide was formerly used as a paint pigment under the name "iodine yellow". It was described by Prosper Mérimée (1830) as "not yet much known in commerce, is as bright as orpimentorchromate of lead. It is thought to be more permanent; but time only can prove its pretension to so essential a quality. It is prepared by precipitating a solution of acetate or nitrate of lead, with potassium iodide: the nitrate produces a more brilliant yellow color."[16] However, due to the toxicity and instability of the compound it is no longer used as such.[16] It may still be used in art for bronzing and in gold-like mosaic tiles.[4]
Lead iodide is very toxic to human health. Ingestion will cause many acute and chronic consequences characteristic of lead poisoning.[30] Lead iodide has been found to be a carcinogen in animals suggesting the same may hold true in humans.[31] Lead iodide is an inhalation hazard, and appropriate respirators should be used when handling powders of lead iodide.
The structure of PbI 2, as determined by X-ray powder diffraction, is primarily hexagonal close-packed system with alternating between layers of lead atoms and iodide atoms, with largely ionic bonding. Weak van der Waals interactions have been observed between lead–iodide layers.[13] The most common stacking forms are 2H and 4H. The 4H polymorph is most common in samples grown from the melt, by precipitation, or by sublimation, whereas the 2H polymorph is usually formed by sol-gel synthesis.[9] The solid can also take an R6 rhombohedral structure.[32]
Lead(II) iodide precipitates when solutions of potassium iodide and lead(II) nitrate are combined
Experiment "golden rain" where iodide of lead(II) was recrystallized from hot solution by cooling, forming crystals of golden-yellow
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^West, Philip W.; Carlton, Jack K. (1952). "The extraction of lead iodide by methyl iso-propyl ketone". Analytica Chimica Acta. 6: 406–411. doi:10.1016/S0003-2670(00)86967-6.
^Ahuja, R.; Arwin, H.; Ferreira Da Silva, A.; Persson, C.; Osorio-Guillén, J. M.; Souza De Almeida, J.; Moyses Araujo, C.; Veje, E.; Veissid, N.; An, C. Y.; Pepe, I.; Johansson, B. (2002). "Electronic and optical properties of lead iodide". Journal of Applied Physics. 92 (12): 7219–7224. Bibcode:2002JAP....92.7219A. doi:10.1063/1.1523145. hdl:10495/11556. S2CID29398039.
^ abcDhiaputra, I.; Permana, B.; Maulana, Y.; Dwi Inayatie, Y.; Purba, Y. R.; Bahtiar, A. (2016). Composition and crystal structure of perovskite films attained from electrodes of used car battery. The 2nd Padjadjaran International Physics Symposium 2015 (PIPS-2015). Vol. 1712. Jatinangor, Indonesia. doi:10.1063/1.4941896.
^ abcShah, K. S.; Olschner, F.; Moy, L. P.; Bennett, P.; Misra, M.; Zhang, J.; Squillante, M. R.; Lund, J. C. (1996). "Lead iodide x-ray detection systems". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. Proceedings of the 9th International Workshop on Room Temperature Semiconductor X- and γ-Ray Detectors, Associated Electronics and Applications. 380 (1–2): 266–270. Bibcode:1996NIMPA.380..266S. doi:10.1016/S0168-9002(96)00346-4.
^US 3764368, Jacobs, J. & Corrigan, R., "Lead iodide film", published 9 October 1973
^ abcEastaugh, N.; Walsh, V.; Chaplin, T.; Siddall, R. (2004). The Pigment Compendium: a Dictionary of Historical Pigments. Butterworth-Heinemann. ISBN978-0750657495.
^Ahmad, S.; Prakash, G. V. (2012). "Fabrication of excitonic luminescent inorganic‑organic hybrid nano and microcrystals". International Conference on Fibre Optics and Photonics. OSA: MPo.40. doi:10.1364/photonics.2012.mpo.40.
^ abMatuchova, M.; Zdansky, K.; Zavadil, J.; Danilewsky, A.; Riesz, F.; Hassan, M.A.S.; Alexiew, D.; Kral, R. (2009). "Study of the influence of the rare-earth elements on the properties of lead iodide". Journal of Crystal Growth. 311 (14): 3557–3562. Bibcode:2009JCrGr.311.3557M. doi:10.1016/j.jcrysgro.2009.04.043.
^Chaudhuri, T.K.; Acharya, H.N. (1982). "Preparation of lead iodide films by iodination of chemically deposited lead sulphide films". Materials Research Bulletin. 17 (3): 279–286. doi:10.1016/0025-5408(82)90074-5.
^Zhu, Xinghua; Wangyang, Peihua; Sun, Hui; Yang, Dingyu; Gao, Xiuying; Tian, Haibo (2016). "Facile growth and characterization of freestanding single crystal PbI2 film". Materials Letters. 180: 59–62. doi:10.1016/j.matlet.2016.05.101.
^Fernelius, W. Conard; Detling, Kenneth D. (1934). "Preparation of crystals of sparingly soluble salts". Journal of Chemical Education. 11 (3): 176. Bibcode:1934JChEd..11..176F. doi:10.1021/ed011p176..
^Scaife, C. W. J.; Cavoli, S. R.; Blanton, T. N.; Morse, M. D.; Sever, B. R.; Willis, W. S.; Suib, S. L. (1990). "Synthesis and characterization of lead(II) iodide grown in space". Chemistry of Materials. 2 (6): 777–780. doi:10.1021/cm00012a034.
^ abcFornaro, L.; Saucedo, E.; Mussio, L.; Yerman, L.; Ma, X.; Burger, A. (2001). "Lead iodide film deposition and characterization". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 458 (1–2): 406–412. Bibcode:2001NIMPA.458..406F. doi:10.1016/S0168-9002(00)00933-5.
^Liu, X.; Ha, S. T.; Zhang, Qing; de la Mata, M.; Magen, C.; Arbiol, J.; Sum, T. C.; Xiong, Q. (2015). "Whispering Gallery Mode Lasing from Hexagonal Shaped Layered Lead Iodide Crystals". ACS Nano. 9 (1): 687–695. doi:10.1021/nn5061207. hdl:10220/38493. PMID25562110.
^Tonn, J.; Matuchova, M.; Danilewsky, A. N.; Cröll, A. (2015). "Removal of oxidic impurities for the growth of high purity lead iodide single crystals". Journal of Crystal Growth. 416: 82–89. Bibcode:2015JCrGr.416...82T. doi:10.1016/j.jcrysgro.2015.01.024.
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