There has been increased concern surrounding exposure to heavy metals due to the evolving understanding of their role in the development of cancer. This review highlights research related to the impact that heavy metals aluminum, arsenic, beryllium, cadmium, lead, mercury, nickel and radium have on human health. Research was collected through PubMed, and it was compiled to assess the current knowledge of exposure sources, types of cancers induced and therapeutic measures for these metals. Furthermore, it was designed to assist in guiding future research efforts with respect to heavy metals and cancer.

Photoinduced charge transfer from an indium tin oxide (ITO) contact into [6,6]-phenyl-C61-butyric acid methyl ester (PC 60 BM) and [6,6]-phenyl-C71-butyric acid methyl ester (PC 70 BM) is measured. For both, chargetransfer peaks are observed for a series of excitation energies below the absorption edge. If charge transfer is blocked using a tunnel barrier or an applied electric field, then the peaks disappear. The observed transitions are similar to those predicted by theoretical calculations of the absorption spectra for negatively charged C 60 and C 70 chains. This observation suggests that charge transfer occurs preferentially at the polaronic transition energies, providing a new means for polaronic state spectroscopy. ■ INTRODUCTIONPCBM ([6,6]-phenyl-C61-butyric acid methyl ester) is a fullerene derivative commonly used in organic solar cells as an electron acceptor due its high electron affinity and relatively strong absorbance in the visible region. 1 In organic solar cells, electron transfer to the PCBM occurs following dissociation of photoexcited electron−hole pairs. 2 On the basis of calculations for isolated C 60 molecules 3 and fullerene chains, 4 it can be concluded that electrons transferred to the PCBM will be stored in a polaronic state. The polaron is the bound state of a charged soliton and a neutral soliton, 5 and is the primary charged species in organic solar cells. 6 Polaron formation is accompanied by the creation of two additional energy levels inside the optical gap. Experimental verification for the existence of polarons comes in part from the observation of optical features brought about by these midgap states. 5 For fullerenes, this includes sub-band-gap peaks in the lowtemperature luminescence of C 60 films 7 and sub-band-gap photoinduced absorption features in both C 60 8 and PCBM. 9 However, because subgap optical peaks can be caused by a number of effects, the identification of the polaronic transitions should ideally correlate subgap features with charge transfer to the fullerene.Here we present the results of a capacitive photocurrent (CPC) spectroscopy technique that is able to detect the appearance of subgap optical transitions directly associated with charge transfer. Optical excitation of the PCBM causes electron transfer from an underlying ITO substrate into the PCBM. The charge transfer is detected by measuring the CPC appearing on a floating probe contact. Peaks are observed in the CPC below the absorption edge of the PCBM. These peaks can be attributed to the subgap transitions appearing in the negatively charged polaronic state. The results show that excitation at the polaronic transition energies promotes both charge transfer and the formation of the polaronic state. ■ EXPERIMENTAL METHODSSample Preparation and Characterization. 80 nm thick ITO-coated glass slides were purchased from Sigma-Aldrich. The slides were ultrasonically cleaned in acetone, IPA, and DI water and then annealed at 45°C for 30 min. Eighteen mg of 99.9% pure PC 60 BM and PC 70 BM was purc...

Photo-induced charge transfer from an Indium Tin Oxide (ITO) contact into [6,6]-phenyl-C61-butyric acid methyl ester (PC 60 BM) and [6,6]-phenyl-C71-butyric acid methyl ester (PC 70 BM) is measured. Charge transfer peaks are observed for a series of excitation energies below the PCBM absorption edge. If charge transfer is blocked using a tunnel barrier or an applied electric field, the peaks disappear. The observed transitions are similar to those predicted by theoretical calculations of the absorption spectra for negatively charged C 60 and C 70 chains. This observation suggests that charge transfer occurs preferentially at the polaronic transition energies in the PCBM, providing a means for polaronic state spectroscopy.