Heteroatom　interaction　of　atomically　thin　nanomaterials　enables　the　improvement　of　electronic　transfer,　band　structure,　and　optical　properties.　Black　phosphorus　quantum　dots　(BP　QDs)　are　considered　to　be　candidate　diagnostic　and/or　therapeutic　agents　due　to　their　innate　biocompatibility　and　exceptional　photochemical　effects.　However,　BP　QDs　are　not　competitive　regarding　second　near-infrared　(NIR-II)　window　medical　diagnosis　and　X-ray　induced　phototherapy.　Here,　an　Nd3+　ion　coordinated　BP　QD　(BPNd)　is　synthesized　with　the　aim　to　sufficiently　improve　its　performances　in　NIR-II　fluorescence　imaging　and　X-ray　induced　photodynamic　therapy,　benefitting　from　the　retrievable　NIR/X-ray　optoelectronic　switching　effects　between　BP　QD　and　Nd3+　ion.　Given　its　ultrasmall　size　and　efficient　cargo　loading　capacity,　BPNd　can　easily　cross　the　blood-brain　barrier　to　precisely　monitor　the　growth　of　glioblastoma　through　intracranial　NIR-II　fluorescence　imaging　and　impede　its　progression　by　specific　X-ray　induced,　synergistic　photodynamic　chemotherapy.